Journal articles on the topic 'Plantarflexor function'
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Palmer, Jacqueline A., Ryan Zarzycki, Susanne M. Morton, Trisha M. Kesar, and Stuart A. Binder-Macleod. "Characterizing differential poststroke corticomotor drive to the dorsi- and plantarflexor muscles during resting and volitional muscle activation." Journal of Neurophysiology 117, no. 4 (April 1, 2017): 1615–24. http://dx.doi.org/10.1152/jn.00393.2016.
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Imbalance of corticomotor excitability between the paretic and nonparetic limbs has been associated with the extent of upper extremity motor recovery poststroke, is greatly influenced by specific testing conditions such as the presence or absence of volitional muscle activation, and may vary across muscle groups. However, despite its clinical importance, poststroke corticomotor drive to lower extremity muscles has not been thoroughly investigated. Additionally, whereas conventional gait rehabilitation strategies for stroke survivors focus on paretic limb foot drop and dorsiflexion impairments, most contemporary literature has indicated that paretic limb propulsion and plantarflexion impairments are the most significant limiters to poststroke walking function. The purpose of this study was to compare corticomotor excitability of the dorsi- and plantarflexor muscles during resting and active conditions in individuals with good and poor poststroke walking recovery and in neurologically intact controls. We found that plantarflexor muscles showed reduced corticomotor symmetry between paretic and nonparetic limbs compared with dorsiflexor muscles in individuals with poor poststroke walking recovery during active muscle contraction but not during rest. Reduced plantarflexor corticomotor symmetry during active muscle contraction was a result of reduced corticomotor drive to the paretic muscles and enhanced corticomotor drive to the nonparetic muscles compared with the neurologically intact controls. These results demonstrate that atypical corticomotor drive exists in both the paretic and nonparetic lower limbs and implicate greater severity of corticomotor impairments to plantarflexor vs. dorsiflexor muscles during muscle activation in stroke survivors with poor walking recovery. NEW & NOTEWORTHY The present study observed that lower-limb corticomotor asymmetry resulted from both reduced paretic and enhanced nonparetic limb corticomotor excitability compared with neurologically intact controls. The most asymmetrical corticomotor drive was observed in the plantarflexor muscles of individuals with poor poststroke walking recovery. This suggests that neural function of dorsi- and plantarflexor muscles in both paretic and nonparetic limbs may play a role in poststroke walking function, which may have important implications when developing targeted poststroke rehabilitation programs to improve walking ability.
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Vandervoort, A. A., and K. C. Hayes. "Plantarflexor muscle function in young and elderly women." European Journal of Applied Physiology and Occupational Physiology 58, no. 4 (1989): 389–94. http://dx.doi.org/10.1007/bf00643514.
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Bojsen-Møller, Jens, Sidse Schwartz, Kari K. Kalliokoski, Taija Finni, and S. Peter Magnusson. "Intermuscular force transmission between human plantarflexor muscles in vivo." Journal of Applied Physiology 109, no. 6 (December 2010): 1608–18. http://dx.doi.org/10.1152/japplphysiol.01381.2009.
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The exact mechanical function of synergist muscles within a human limb in vivo is not well described. Recent studies indicate the existence of a mechanical interaction between muscle actuators that may have functional significance and further play a role for injury mechanisms. The purpose of the present study was to investigate if intermuscular force transmission occurs within and between human plantarflexor muscles in vivo. Seven subjects performed four types of either active contractile tasks or passive joint manipulations: passive knee extension, voluntary isometric plantarflexion, voluntary isometric hallux flexion, passive hallux extension, and selective percutaneous stimulation of the gastrocnemius medialis (MG). In each experiment plantar- and hallux flexion force and corresponding EMG activity were sampled. During all tasks ultrasonography was applied at proximal and distal sites to assess task-induced tissue displacement (which is assumed to represent loading) for the plantarflexor muscles [MG, soleus (SOL), and flexor hallucis longus (FHL)]. Selective MG stimulation and passive knee extension resulted in displacement of both the MG and SOL muscles. Minimal displacement of the triceps surae muscles was seen during passive hallux extension. Large interindividual differences with respect to deep plantarflexor activation during voluntary contractions were observed. The present results suggest that force may be transmitted between the triceps surae muscles in vivo, while only limited evidence was provided for the occurrence of force transfer between the triceps surae and the deeper-lying FHL.
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De Jaeger, Dominique, Venus Joumaa, and Walter Herzog. "Intermittent stretch training of rabbit plantarflexor muscles increases soleus mass and serial sarcomere number." Journal of Applied Physiology 118, no. 12 (June 15, 2015): 1467–73. http://dx.doi.org/10.1152/japplphysiol.00515.2014.
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In humans, enhanced joint range of motion is observed after static stretch training and results either from an increased stretch tolerance or from a change in the biomechanical properties of the muscle-tendon unit. We investigated the effects of an intermittent stretch training on muscle biomechanical and structural variables. The left plantarflexors muscles of seven anesthetized New Zealand (NZ) White rabbits were passively and statically stretched three times a week for 4 wk, while the corresponding right muscles were used as nonstretched contralateral controls. Before and after the stretching protocol, passive torque produced by the left plantarflexor muscles as a function of the ankle angle was measured. The left and right plantarflexor muscles were harvested from dead rabbits and used to quantify possible changes in muscle structure. Significant mass and serial sarcomere number increases were observed in the stretched soleus but not in the plantaris or medial gastrocnemius. This difference in adaptation between the plantarflexors is thought to be the result of their different fiber type composition and pennation angles. Neither titin isoform nor collagen amount was modified in the stretched compared with the control soleus muscle. Passive torque developed during ankle dorsiflexion was not modified after the stretch training on average, but was decreased in five of the seven experimental rabbits. Thus, an intermittent stretching program similar to those used in humans can produce a change in the muscle structure of NZ White rabbits, which was associated in some rabbits with a change in the biomechanical properties of the muscle-tendon unit.
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Hullfish, Todd J., Kathryn M. O’Connor, and Josh R. Baxter. "Medial gastrocnemius muscle remodeling correlates with reduced plantarflexor kinetics 14 weeks following Achilles tendon rupture." Journal of Applied Physiology 127, no. 4 (October 1, 2019): 1005–11. http://dx.doi.org/10.1152/japplphysiol.00255.2019.
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Deficits in plantarflexor kinetics are associated with poor outcomes in patients following Achilles tendon rupture. In this longitudinal study, we analyzed the fascicle length and pennation angle of the medial gastrocnemius muscle and the length of the Achilles tendon using ultrasound imaging. To determine the relationship between muscle remodeling and deficits in plantarflexor kinetics measured at 14 wk after injury, we correlated the reduction in fascicle length and increase in pennation angle with peak torque measured during isometric and isokinetic plantarflexor contractions. We found that the medial gastrocnemius underwent an immediate change in structure, characterized by decreased length and increased pennation of the muscle fascicles. This decrease in fascicle length was coupled with an increase in tendon length. These changes in muscle-tendon structure persisted throughout the first 14 wk following rupture. Deficits in peak plantarflexor torque were moderately correlated with decreased fascicle length at 120 degrees per second ( R2 = 0.424, P = 0.057) and strongly correlated with decreased fascicle length at 210 degrees per second ( R2 = 0.737, P = 0.003). However, increases in pennation angle did not explain functional deficits. These findings suggest that muscle-tendon structure is detrimentally affected following Achilles tendon rupture. Plantarflexor power deficits are positively correlated with the magnitude of reductions in fascicle length. Preserving muscle structure following Achilles tendon rupture should be a clinical priority to maintain plantarflexor kinetics. NEW & NOTEWORTHY In our study, we found that when the Achilles tendon ruptures due to excessive biomechanical loading, the neighboring skeletal muscle undergoes rapid changes in its configuration. The magnitude of this muscle remodeling explains the amount of ankle power loss demonstrated by these patients once their Achilles tendons are fully healed. These findings highlight the interconnected relationship between muscle and tendon. Isolated injuries to the tendon stimulate detrimental changes to the muscle, thereby limiting joint-level function.
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Furlong, L. A. M., and A. J. Harrison. "Sex-related differences in plantarflexor function during repeated stretch-shortening cycle loading." Muscle Ligaments and Tendons Journal 08, no. 01 (January 2019): 76. http://dx.doi.org/10.32098/mltj.01.2018.10.
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Hinds, Robyn, Jessica Blank, Sunita Mathur, Chris M. Gregory, Trevor Lentz, Susan M. Tillman, Glenn A. Walter, and Krista Vandenborne. "Improvements In Plantarflexor Size And Function Following Rehabilitation After Lower Leg Injury." Medicine & Science in Sports & Exercise 41 (May 2009): 286–87. http://dx.doi.org/10.1249/01.mss.0000355425.73812.ec.
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McCall, G. E., C. Goulet, G. E. Boorman, J. A. Hodgson, R. R. Roy, M. C. Greenisen, and V. R. Edgerton. "MAINTENANCE OF PLANTARFLEXOR MUSCLE FUNCTION IN HUMANS DURING A 17-DAY SPACEFLIGHT 163." Medicine & Science in Sports & Exercise 29, Supplement (May 1997): 28. http://dx.doi.org/10.1097/00005768-199705001-00163.
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Selsby, Joshua T., Pedro Acosta, Meg M. Sleeper, Elisabeth R. Barton, and H. Lee Sweeney. "Long-term wheel running compromises diaphragm function but improves cardiac and plantarflexor function in the mdx mouse." Journal of Applied Physiology 115, no. 5 (September 1, 2013): 660–66. http://dx.doi.org/10.1152/japplphysiol.00252.2013.
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Dystrophin-deficient muscles suffer from free radical injury, mitochondrial dysfunction, apoptosis, and inflammation, among other pathologies that contribute to muscle fiber injury and loss, leading to wheelchair confinement and death in the patient. For some time, it has been appreciated that endurance training has the potential to counter many of these contributing factors. Correspondingly, numerous investigations have shown improvements in limb muscle function following endurance training in mdx mice. However, the effect of long-term volitional wheel running on diaphragm and cardiac function is largely unknown. Our purpose was to determine the extent to which long-term endurance exercise affected dystrophic limb, diaphragm, and cardiac function. Diaphragm specific tension was reduced by 60% ( P < 0.05) in mice that performed 1 yr of volitional wheel running compared with sedentary mdx mice. Dorsiflexor mass (extensor digitorum longus and tibialis anterior) and function (extensor digitorum longus) were not altered by endurance training. In mice that performed 1 yr of volitional wheel running, plantarflexor mass (soleus and gastrocnemius) was increased and soleus tetanic force was increased 36%, while specific tension was similar in wheel-running and sedentary groups. Cardiac mass was increased 15%, left ventricle chamber size was increased 20% (diastole) and 18% (systole), and stroke volume was increased twofold in wheel-running compared with sedentary mdx mice. These data suggest that the dystrophic heart may undergo positive exercise-induced remodeling and that limb muscle function is largely unaffected. Most importantly, however, as the diaphragm most closely recapitulates the human disease, these data raise the possibility of exercise-mediated injury in dystrophic skeletal muscle.
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Furlong, Laura-Anne M., and Andrew J. Harrison. "Differences in plantarflexor function during a stretch-shortening cycle task due to limb preference." Laterality: Asymmetries of Body, Brain and Cognition 20, no. 2 (May 30, 2014): 128–40. http://dx.doi.org/10.1080/1357650x.2014.921688.
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White, L. J., S. C. McCoy, V. Castellano, G. Gutierrez, J. E. Stevens, G. A. Walter, and K. Vandenborne. "Resistance training improves strength and functional capacity in persons with multiple sclerosis." Multiple Sclerosis Journal 10, no. 6 (December 2004): 668–74. http://dx.doi.org/10.1191/1352458504ms1088oa.
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The purpose of this study was to evaluate the effect of an eight-week progressive resistance training programme on lower extremity strength, ambulatory function, fatigue and self-reported disability in multiple sclerosis (MS) patients (mean disability score 3.79-0.8). Eight MS subjects volunteered for twice weekly training sessions. During the first two weeks, subjects completed one set of 8 -10 reps at 50% of maximal voluntary contraction (MVC) of knee flexion, knee extension and plantarflexion exercises. In subsequent sessions, the subjects completed one set of 10 -15 repetitions at 70% of MVC. The resistance was increased by 2 -5% when subjects completed 15 repetitions in consecutive sessions. Isometric strength of the quadriceps, hamstring, plantarflexor and dorsiflexor muscle groups was assessed before and after the training programme using an isokinetic dynamometer. Magnetic resonance images of the thigh were acquired before and after the exercise programme as were walking speed (25-ft), number of steps in 3 min, and self-reported fatigue and disability. Knee extension (7.4%), plantarflexion (52%) and stepping performance (8.7%) increased significantly (PB-0.05). Self-reported fatigue decreased (PB-0.05) and disability tended to decrease (P -0.07) following the training programme. MS patients are capable of making positive adaptations to resistance training that are associated with improved ambulation and decreased fatigue.
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Furlong, Laura-Anne M., and Andrew J. Harrison. "Reliability and consistency of plantarflexor stretch-shortening cycle function using an adapted force sledge apparatus." Physiological Measurement 34, no. 4 (March 22, 2013): 437–48. http://dx.doi.org/10.1088/0967-3334/34/4/437.
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Kurz, Max J., Elizabeth Heinrichs-Graham, Katherine M. Becker, and Tony W. Wilson. "The magnitude of the somatosensory cortical activity is related to the mobility and strength impairments seen in children with cerebral palsy." Journal of Neurophysiology 113, no. 9 (May 2015): 3143–50. http://dx.doi.org/10.1152/jn.00602.2014.
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The noted disruption of thalamocortical connections and abnormalities in tactile sensory function has resulted in a new definition of cerebral palsy (CP) that recognizes the sensorimotor integration process as central to the motor impairments seen in these children. Despite this updated definition, the connection between a child's motor impairments and somatosensory processing remains almost entirely unknown. In this investigation, we explored the relationship between the magnitude of neural activity within the somatosensory cortices, the strength of the ankle plantarflexors, and the gait spatiotemporal kinematics of a group of children with CP and a typically developing matched cohort. Our results revealed that the magnitude of somatosensory cortical activity in children with CP had a strong positive relationship with the ankle strength, step length, and walking speed. These results suggest that stronger activity within the somatosensory cortices in response to foot somatosensations was related to enhanced ankle plantarflexor strength and improved mobility in the children with CP. These results provide further support for the notion that children with CP exhibit, not only musculoskeletal deficits, but also somatosensory deficits that potentially contribute to their overall functional mobility and strength limitations.
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Willy, Richard W., Annelie Brorsson, Hayley C. Powell, John D. Willson, Roy Tranberg, and Karin Grävare Silbernagel. "Elevated Knee Joint Kinetics and Reduced Ankle Kinetics Are Present During Jogging and Hopping After Achilles Tendon Ruptures." American Journal of Sports Medicine 45, no. 5 (February 10, 2017): 1124–33. http://dx.doi.org/10.1177/0363546516685055.
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Background: Deficits in plantarflexor function are common after an Achilles tendon rupture. These deficits may result in an altered distribution of joint loads during lower extremity tasks. Hypothesis: We hypothesized that, regardless of treatment, the Achilles tendon–ruptured limb would exhibit deficits in ankle kinematics and joint power while exhibiting elevated knee joint power and patellofemoral joint loads during walking, jogging, and hopping. We further hypothesized that this loading pattern would be most evident during jogging and hopping. Study Design: Controlled laboratory study. Methods: Thirty-four participants (17 participants treated surgically, 17 treated nonsurgically) were tested at a mean 6.1 ± 2.0 years after an Achilles tendon rupture. Lower extremity kinematics and kinetics were assessed while participants completed walking, jogging, and single-legged hopping trials. Patellofemoral joint stress was calculated via a musculoskeletal model. Data were analyzed via mixed-model repeated analyses of variance (α = .05) and the limb symmetry index (LSI). Results: No differences ( P ≥ .05) were found between the surgical and nonsurgical groups. In both groups, large side-to-side deficits in the plantarflexion angle at toeoff (LSI: 53.5%-73.9%) were noted during walking, jogging, and hopping in the involved limb. Side-to-side deficits in the angular velocity were only present during jogging (LSI: 93.5%) and hopping (LSI: 92.5%). This pattern was accompanied by large deficits in eccentric (LSI: 80.8%-94.7%) and concentric (LSI: 82.2%-84.7%) ankle joint powers in the involved limb during all tasks. Interestingly, only jogging and hopping demonstrated greater knee joint loads when compared with the uninvolved limb. Concentric knee power was greater during jogging (LSI: 117.2%) and hopping (LSI: 115.9%) compared with the uninvolved limb. Similarly, peak patellofemoral joint stress was greater in the involved limb during jogging (LSI: 107.5%) and hopping (LSI: 107.1%), while only hopping had a greater loading rate of patellofemoral joint stress (LSI: 110.9%). Conclusion: Considerable side-to-side deficits in plantarflexor function were observed during walking, jogging, and hopping in patients after an Achilles tendon rupture. As a possible compensation, increased knee joint loads were present but only during jogging and hopping. Clinical Relevance: These data suggest that after an Achilles tendon rupture, patients may be susceptible to greater mechanical loading of the knee during sporting tasks, regardless of surgical or nonsurgical treatment.
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Schmidtbauer, Kelly A., E. Russell Esposito, and Jason M. Wilken. "Ankle–foot orthosis alignment affects running mechanics in individuals with lower limb injuries." Prosthetics and Orthotics International 43, no. 3 (February 14, 2019): 316–24. http://dx.doi.org/10.1177/0309364619826386.
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Background: Individuals with severe lower extremity injuries often require ankle–foot orthoses to return to normal activities. Ankle–foot orthoses alignment is a key consideration during the clinical fitting process and may be particularly important during dynamic activities such as running. Objective: To investigate how 3° changes in sagittal plane ankle–foot orthoses alignment affect running mechanics. Study design: Controlled laboratory study. Methods: Twelve participants with unilateral lower limb injury ran overground and lower extremity running mechanics were assessed. Participants wore their passive-dynamic ankle–foot orthoses in three alignments: clinically fit neutral, 3° plantarflexed from clinically fit neutral, and 3° dorsiflexed from clinically fit neutral. Results: The 3° changes in sagittal alignment significantly influenced ankle mechanics during running. The plantarflexed alignment significantly decreased the peak ankle plantarflexor moment, peak knee extensor moment, and peak ankle and knee power absorption and generation compared to more dorsiflexed alignments. Alignment also altered footstrike angle, with dorsiflexed alignments associated with a more dorsiflexed footstrike pattern and plantarflexed alignments toward a more plantarflexed footstrike pattern. However, alignment did not influence loading rate. Conclusion: Small changes in ankle–foot orthoses alignment significantly altered running mechanics, including footstrike angle, and knee extensor moments. Understanding how ankle–foot orthoses design parameters affect running mechanics may aid the development of evidence-based prescription guidelines and improve function for ankle–foot orthoses users who perform high-impact activities. Clinical relevance Understanding how ankle–foot orthoses alignment impacts biomechanics should be a consideration when fitting passive-dynamic devices for higher impact activities, such as running. Individual running styles, including footstrike patterns, may be affected by small changes in alignment.
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Yu, W., Y. Ikemoto, R. Acharya, and J. Unoue. "Comparing normal walking and compensated walking: Their stability and perturbation resistance. A simulation study." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 224, no. 7 (December 15, 2009): 891–901. http://dx.doi.org/10.1243/09544119jeim627.
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People usually develop different kinds of compensated gait in response to local function deficits, such as muscle weakness, spasticity in specific muscle groups, or joint stiffness, in order to overcome the falling risk factors. Compensated walking has been analysed empirically in the impaired gait analysis area. However, the compensation could be identified spatially and temporally. The stability and perturbation resistance of compensated walking have not been analysed quantitatively. In this research, a biomimetic human walking simulator was employed to model one individual paraplegic subject with plantarflexor spasticity. The pes equinus was expressed by biasing the outputs of plantarflexor neurons corresponding to the spastic muscles. Then, the compensatory mechanism was explored by adjusting the outputs of the other muscles. It was shown that this approach can be used for quantitative analysis of the spastic gait and compensated walking. Thus, this research can improve the understanding of the behaviour of compensated walking, bringing insights not only for building useful walking assist systems with high safety but also for designing effective rehabilitation interventions.
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Addison, Odessa. "FRAILTY." Innovation in Aging 3, Supplement_1 (November 2019): S574. http://dx.doi.org/10.1093/geroni/igz038.2128.
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Abstract The ability to safely maintain mobility function with aging is critical as immobility and falls are among the top reasons for long-term care admissions. One potential cause for these functional deficits are muscle composition changes resulting in reductions in muscle mass, strength and power, ultimately contributing to the development of frailty. While the majority of work examining muscle composition and mobility changes with aging have focused on the quadriceps and ankle plantarflexor/dorsiflexor muscles, accumulating evidence suggests that deficits involving the proximal hip muscles may be particularly harmful to balance and mobility functions leading to falls, hip fractures, and frailty. We will discuss muscle changes that occur with aging and frailty, the implications on mobility, and the effects of potential exercise interventions on muscle structure and function as well as their ability to improve functional mobility.
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Javidi, Mehrdad, Craig P. McGowan, and David C. Lin. "Estimation of the force–velocity properties of individual muscles from measurement of the combined plantarflexor properties." Journal of Experimental Biology 223, no. 18 (July 17, 2020): jeb219980. http://dx.doi.org/10.1242/jeb.219980.
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ABSTRACTThe force–velocity (F–V) properties of isolated muscles or muscle fibers have been well studied in humans and other animals. However, determining properties of individual muscles in vivo remains a challenge because muscles usually function within a synergistic group. Modeling has been used to estimate the properties of an individual muscle from the experimental measurement of the muscle group properties. While this approach can be valuable, the models and the associated predictions are difficult to validate. In this study, we measured the in situ F–V properties of the maximally activated kangaroo rat plantarflexor group and used two different assumptions and associated models to estimate the properties of the individual plantarflexors. The first model (Mdl1) assumed that the percent contributions of individual muscles to group force and power were based upon the muscles' cross-sectional area and were constant across the different isotonic loads applied to the muscle group. The second model (Mdl2) assumed that the F–V properties of the fibers within each muscle were identical, but because of differences in muscle architecture, the muscles' contributions to the group properties changed with isotonic load. We compared the two model predictions with independent estimates of the muscles' contributions based upon sonomicrometry measurements of muscle length. We found that predictions from Mdl2 were not significantly different from sonomicrometry-based estimates while those from Mdl1 were significantly different. The results of this study show that incorporating appropriate fiber properties and muscle architecture is necessary to parse the individual muscles' contributions to the group F–V properties.
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Gallinger, Tessa L., Jared R. Fletcher, and Brian R. MacIntosh. "Mechanisms of reduced plantarflexor function in Cerebral palsy: smaller triceps surae moment arm and reduced muscle force." Journal of Biomechanics 110 (September 2020): 109959. http://dx.doi.org/10.1016/j.jbiomech.2020.109959.
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Arch, Elisa S., and Darcy S. Reisman. "Passive-Dynamic Ankle-Foot Orthoses with Personalized Bending Stiffness Can Enhance Net Plantarflexor Function for Individuals Poststroke." Journal of Prosthetics and Orthotics 28, no. 2 (April 2016): 60–67. http://dx.doi.org/10.1097/jpo.0000000000000089.
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Kremer, Theodore R., Linda R. Van Dillen, and Joanne M. Wagner. "Dynamometer-based measure of spasticity confirms limited association between plantarflexor spasticity and walking function in persons with multiple sclerosis." Journal of Rehabilitation Research and Development 51, no. 6 (2014): 975–84. http://dx.doi.org/10.1682/jrrd.2013.08.0186.
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Franz, Jason R., and Darryl G. Thelen. "Depth-dependent variations in Achilles tendon deformations with age are associated with reduced plantarflexor performance during walking." Journal of Applied Physiology 119, no. 3 (August 1, 2015): 242–49. http://dx.doi.org/10.1152/japplphysiol.00114.2015.
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The anatomical arrangement of the Achilles tendon (AT), with distinct fascicle bundles arising from the gastrocnemius and soleus muscles, may facilitate relatively independent behavior of the triceps surae muscles. A reduced capacity for sliding between adjacent tendon fascicles with age may couple gastrocnemius and soleus muscle behavior, thereby potentially contributing to diminished plantarflexor performance commonly observed in old adults. Nine healthy young (mean age, 23.9 yr) and eight healthy old (69.9 yr) adults walked at three speeds (0.75, 1.00, and 1.25 m/s) on a force-sensing treadmill. We coupled dynamic ultrasound imaging of the free AT with motion capture and inverse dynamic analyses to compute, in part: 1) depth-dependent variations in AT tissue displacements and elongations and 2) net ankle joint kinetics during push-off. The difference in displacements between superficial and deep AT regions, and in their corresponding elongations, did not differ between old and young adults at the slower two walking speeds ( P > 0.61). However, old adults walked with 41% smaller depth-dependent variations in free AT displacements and elongations at 1.25 m/s ( P = 0.02). These more uniform tendon deformations in old adults most strongly correlated with reduced peak ankle moment ( R2= 0.40), but also significantly correlated with reduced peak power generation ( R2= 0.15) and positive ankle work during push-off ( R2= 0.19) ( P > 0.01). Our findings: 1) demonstrate a potential role for nonuniform AT deformations in governing gastrocnemius and soleus muscle-tendon function and 2) allude to altered tendon behavior that may contribute to the age-related reduction in plantarflexor performance during walking.
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Masood, Tahir, Kari Kalliokoski, Jens Bojsen-Møller, S. Peter Magnusson, and Taija Finni. "Plantarflexor muscle function in healthy and chronic Achilles tendon pain subjects evaluated by the use of EMG and PET imaging." Clinical Biomechanics 29, no. 5 (May 2014): 564–70. http://dx.doi.org/10.1016/j.clinbiomech.2014.03.003.
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Edgerton, V. R., G. E. McCall, J. A. Hodgson, J. Gotto, C. Goulet, K. Fleischmann, and R. R. Roy. "Sensorimotor adaptations to microgravity in humans." Journal of Experimental Biology 204, no. 18 (September 15, 2001): 3217–24. http://dx.doi.org/10.1242/jeb.204.18.3217.
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SUMMARY Motor function is altered by microgravity, but little detail is available as to what these changes are and how changes in the individual components of the sensorimotor system affect the control of movement. Further, there is little information on whether the changes in motor performance reflect immediate or chronic adaptations to changing gravitational environments. To determine the effects of microgravity on the neural control properties of selected motor pools, four male astronauts from the NASA STS-78 mission performed motor tasks requiring the maintenance of either ankle dorsiflexor or plantarflexor torque. Torques of 10 or 50% of a maximal voluntary contraction (MVC) were requested of the subjects during 10° peak-to-peak sinusoidal movements at 0.5Hz. When 10% MVC of the plantarflexors was requested, the actual torques generated in-flight were similar to pre-flight values. Post-flight torques were higher than pre- and in-flight torques. The actual torques when 50% MVC was requested were higher in- and post-flight than pre-flight. Soleus (Sol) electromyographic (EMG) amplitudes during plantarflexion were higher in-flight than pre- or post-flight for both the 10 and 50% MVC tasks. No differences in medial gastrocnemius (MG) EMG amplitudes were observed for either the 10 or 50% MVC tasks. The EMG amplitudes of the tibialis anterior (TA), an antagonist to plantarflexion, were higher in- and post-flight than pre-flight for the 50% MVC task. During the dorsiflexion tasks, the torques generated in both the 10 and 50% MVC tasks did not differ pre-, in- and post-flight. TA EMG amplitudes were significantly higher in- than pre-flight for both the 10 or 50% MVC tasks, and remained elevated post-flight for the 50% MVC test. Both the Sol and MG EMG amplitudes were significantly higher in-flight than either pre- or post-flight for both the 10 and 50% MVC tests. These data suggest that the most consistent response to space flight was an elevation in the level of contractions of agonists and antagonists when attempting to maintain constant torques at a given level of MVC. Also, the chronic levels of EMG activity in selected ankle flexor and extensor muscles during space flight and during routine activities on Earth were recorded. Compared with pre- and post-flight values, there was a marked increase in the total EMG activity of the TA and the Sol and no change in the MG EMG activity in-flight. These data indicate that space flight, as occurs on shuttle missions, is a model of elevated activation of both flexor and extensor muscles, probably reflecting the effects of programmed work schedules in flight rather than a direct effect of microgravity.
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Paxton, Roger J., Caitlin Feldman-Kothe, Megan K. Trabert, Leah N. Hitchcock, Raoul F. Reiser, and Brian L. Tracy. "Postural Steadiness and Ankle Force Variability in Peripheral Neuropathy." Motor Control 20, no. 3 (July 2016): 266–84. http://dx.doi.org/10.1123/mc.2014-0072.
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Introduction:The purpose was to determine the effect of peripheral neuropathy (PN) on motor output variability for ankle muscles of older adults, and the relation between ankle motor variability and postural stability in PN patients.Methods:Older adults with (O-PN) and without PN (O), and young adults (Y) underwent assessment of standing postural stability and ankle muscle force steadiness.Results:O-PN displayed impaired ankle muscle force control and postural stability compared with O and Y groups. For O-PN, the amplitude of plantarflexor force fluctuations was moderately correlated with postural stability under no-vision conditions (r = .54, p = .01).Discussion:The correlation of variations in ankle force with postural stability in PN suggests a contribution of ankle muscle dyscontrol to the postural instability that impacts physical function for older adults with PN.
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Furlong, Laura-Anne M., and Andrew J. Harrison. "Corrigendum: Reliability and consistency of plantarflexor stretch-shortening cycle function using an adapted force sledge apparatus (2013 Physiological Measurement 34 437)." Physiological Measurement 35, no. 10 (September 22, 2014): 2177. http://dx.doi.org/10.1088/0967-3334/35/10/2177.
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Hill, Mathew William, Matthew Roberts, Michael James Price, and Anthony David Kay. "Association between knee extensor and ankle plantarflexor muscle thickness and echo intensity with postural sway, mobility and physical function in older adults." Experimental Gerontology 150 (July 2021): 111385. http://dx.doi.org/10.1016/j.exger.2021.111385.
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O’Connor, Kathryn M., Todd J. Hullfish, and Josh R. Baxter. "Gastrocnemius Muscle Structure Remodels Within the First Month Following Acute Achilles Tendon Rupture." Foot & Ankle Orthopaedics 4, no. 4 (October 1, 2019): 2473011419S0032. http://dx.doi.org/10.1177/2473011419s00324.
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Category: Sports, Trauma, Achilles Tendon Introduction/Purpose: Two out of three patients Achilles tendon ruptures have limited plantarflexor function 1-year following Achilles tendon rupture. While tendon elongation has been reported as a possible mechanism of functional deficits, the effects of rupture on plantarflexor muscle structure has not been as rigorously investigated. A recent study found that gastrocnemius fascicle length was decreased 6-months following Achilles tendon rupture compared to the uninjured limb. However, the changes in muscle structure following the first month of injury – when the healing tendon is most susceptible to elongation – has not yet been established. The purpose of this study was to quantify the structural changes to the medial gastrocnemius in patients who suffered acute Achilles tendon ruptures and were treated non-operatively. Methods: To test our hypothesis that plantarflexor structure would undergo rapid remodeling following Achilles tendon rupture, we quantified muscle structure in ten patients (9 male, Age: 44 ± 12; BMI: 28.6 ± 6.5) who provide informed written consent in this IRB approved study. We acquired B-mode ultrasound images of the medial gastrocnemius muscle at the initial presentation (week 0), two weeks, and four weeks following the injury. The same investigator acquired all the ultrasound images and measured fascicle length, pennation angle, muscle thickness, and echo intensity. These measurements had a coefficient of variation less than 10%. We compared these structural measurements of the injured muscle at each time point with the contralateral muscle scans at the initial presentation using paired t-tests. Results: Gastrocnemius muscle structure following an acute Achilles tendon rupture differed with the healthy-contralateral muscle throughout the first four weeks following injury (Figure). Fascicle length was 15% shorter (P < 0.001) and pennation angle was 21% greater (P < 0.001) at the presentation of injury (week 0). These differences in fascicle length (P < 0.001) and pennation angle persisted throughout the 4 weeks after the injury (P < 0.008). Muscle thickness changes were not detected at any of the post-injury visits. Muscle quality, measured as mean echo intensity, was 8% lower in the injured limb immediately (P= 0.008) and 11% lower 2 weeks following injury (P < 0.001). At week 4 muscle quality had returned to within 1% of the contralateral limb (P = 0.393). Conclusion: Our findings support our hypothesis that the gastrocnemius muscle fascicles of the affected side would demonstrate shorter length and greater pennation angle than the contralateral control muscle. These findings are a preliminary set of data from a larger clinical cohort of patients that were enrolled in an ongoing 1-year long prospective study. Achilles tendon ruptures elicit rapid changes in the configuration and quality of the medial gastrocnemius, which may explain long-term functional deficits.
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Hösl, Matthias, Harald Böhm, Justine Eck, Leonhard Döderlein, and Adamantios Arampatzis. "Effects of backward-downhill treadmill training versus manual static plantarflexor stretching on muscle-joint pathology and function in children with spastic Cerebral Palsy." Gait & Posture 65 (September 2018): 121–28. http://dx.doi.org/10.1016/j.gaitpost.2018.07.171.
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Brooks, Matthew J., Ameena Hajira, Junaith S. Mohamed, and Stephen E. Alway. "Voluntary wheel running increases satellite cell abundance and improves recovery from disuse in gastrocnemius muscles from mice." Journal of Applied Physiology 124, no. 6 (June 1, 2018): 1616–28. http://dx.doi.org/10.1152/japplphysiol.00451.2017.
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Reloading of atrophied muscles after hindlimb suspension unloading (HSU) can induce injury and prolong recovery. Low-impact exercise, such as voluntary wheel running, has been identified as a nondamaging rehabilitation therapy in rodents, but its effects on muscle function, morphology, and satellite cell activity after HSU are unclear. This study tested the hypothesis that low-impact wheel running would increase satellite cell proliferation and improve recovery of muscle structure and function after HSU in mice. Young adult male and female C57BL/6 mice ( n = 6/group) were randomly placed into five groups. These included HSU without recovery (HSU), normal ambulatory recovery for 14 days after HSU (HSU+NoWR), and voluntary wheel running recovery for 14 days after HSU (HSU+WR). Two control groups were used: nonsuspended mouse cage controls (Control) and voluntary wheel running controls (ControlWR). Satellite cell activation was evaluated by providing mice 5-bromo-2′-deoxyuridine (BrdU) in their drinking water. As expected, HSU significantly reduced in vivo maximal force, decreased in vivo fatigability, and decreased type I and IIa myosin heavy chain (MHC) abundance in plantarflexor muscles. HSU+WR mice significantly improved plantarflexor fatigue resistance, increased type I and IIa MHC abundance, increased fiber cross-sectional area, and increased the percentage of type I and IIA muscle fibers in the gastrocnemius muscle. HSU+WR mice also had a significantly greater percentage of BrdU-positive and Pax 7-positive nuclei inside muscle fibers and a greater MyoD-to-Pax 7 protein ratio compared with HSU+NoWR mice. The mechanotransduction protein Yes-associated protein (YAP) was elevated with reloading after HSU, but HSU+WR mice had lower levels of the inactive phosphorylated YAPserine127, which may have contributed to increased satellite cell activation with reloading after HSU. These results indicate that voluntary wheel running increased YAP signaling and satellite cell activity after HSU and this was associated with improved recovery. NEW & NOTEWORTHY Although satellite cell involvement in muscle remodeling has been challenged, the data in this study suggest that voluntary wheel running increased satellite cell activity and suppressed Yes-associated protein (YAP) protein relative to no wheel running and this was associated with improved muscle recovery of force, fatigue resistance, expression of type I myosin heavy chain, and greater fiber cross-sectional area after disuse.
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Joo, So Young, Seung Yeol Lee, Yoon Soo Cho, Kuem Ju Lee, and Cheong Hoon Seo. "Effects of Robot-Assisted Gait Training in Patients with Burn Injury on Lower Extremity: A Single-Blind, Randomized Controlled Trial." Journal of Clinical Medicine 9, no. 9 (August 31, 2020): 2813. http://dx.doi.org/10.3390/jcm9092813.
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This study investigated the effects of robot-assisted gait training (RAGT) on gait function in burn patients. Briefly, 40 burn patients were randomly divided into an RAGT group or a conventional training (CON) group. SUBAR® (Cretem, Korea) is a wearable robot with a footplate that simulates normal gait cycles. The RAGT group underwent 30 min of robot-assisted training using SUBAR® with 30 min of conventional physiotherapy once a day, 5 days a week for 12 weeks. Patients in the CON group received 30 min of overground gait training and range-of-motion (ROM) exercises twice a day for 5 days a week for 12 weeks. The RAGT group and the CON group underwent 60 min of training per day. The intervention frequency and duration did not differ between the RAGT group and the CON group. The main outcomes were functional ambulatory category (FAC); 6-min walking test (6MWT); visual analogue scale (VAS) during gait movement; ROM; and isometric forces of bilateral hip, knee, and ankle muscles before and after 12 weeks of training. The results of the VAS, FAC, and 6MWT (8.06 ± 0.66, 1.76 ± 0.56, and 204.41 ± 85.60) before training in the RAGT group improved significantly (4.41 ± 1.18, 4.18 ± 0.39, and 298.53 ± 47.75) after training (p < 0.001, p < 0.001, and p < 0.001). The results of the VAS, FAC, and 6MWT (8.00 ± 1.21, 1.75 ± 0.58, and 220.94 ± 116.88) before training in the CON group improved significantly (5.00 ± 1.03, 3.81 ± 1.05, and 272.19 ± 110.14) after training (p < 0.001, p < 0.001, and p = 0.05). There were differences in the improvement of results of the VAS, FAC, and 6MWT between groups after training, but they were not statistically significant (p = 0.23, p = 0.14, and p = 0.05). The isometric strengths of the right hip extensor (p = 0.02), bilateral knee flexor (p = 0.04 in the right, and p = 0.001 in the left), bilateral knee extensor (p = 0.003 in the right, and p = 0.002 in the left), bilateral ankle dorsiflexor (p = 0.04 in the right, and p = 0.02 in the left), and bilateral ankle plantarflexor (p = 0.001 in the right, and p = 0.008 in the left) after training were significantly improved compared with those before training in the RAGT group. The ROMs of the right knee extension (p = 0.03) and bilateral ankle plantarflexion (p = 0.008 in the right, and p = 0.03 in the left) were significantly improved compared with measurements before training in the RAGT. There were no significant differences of the isometric strengths and ROMs of the bilateral hip, knee, and ankle muscles after training in the CON group. There were significant improvements in the isometric strengths of the left knee flexor (p = 0.01), left ankle dorsiflexor (p = 0.01), and left ankle plantarflexor (p = 0.003) between the two groups. The results suggested that RAGT is effective to facilitate early recovery of muscles strength after a burn injury. This is the first study to evaluate the effectiveness of RAGT in patients with burns compared with those receiving conventional training. The absence of complications in burn patients provides an opportunity to enlarge the application area of RAGT.
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Waugh, C. M., and A. Scott. "Substantial Achilles adaptation following strength training has no impact on tendon function during walking." PLOS ONE 16, no. 7 (July 29, 2021): e0255221. http://dx.doi.org/10.1371/journal.pone.0255221.
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Tendons are responsive to mechanical loading and their properties are often the target of intervention programs. The tendon’s mechanical properties, particularly stiffness, also govern its function, therefore changes to these properties could have substantial influence on energy-saving mechanisms during activities utilizing the stretch-shortening cycle. We investigated Achilles tendon (AT) function in vivo during walking with respect to a training intervention that elicited significant increases in AT stiffness. 14 men and women completed 12-weeks of isometric plantarflexor strength training that increased AT stiffness, measured during isometric MVC, by ~31%. Before and after the intervention, participants walked shod at their preferred velocity on a fully-instrumented treadmill. Movement kinematics, kinetics and displacement of the gastrocnemius medialis muscle-tendon junction were captured synchronously using 3D motion capture and ultrasound imaging, respectively. A MANOVA test was used to examine changes in AT force, stress, strain, stiffness, Young’s modulus, hysteresis and strain energy, measured during walking, before and following strength training. All were non-significant for a main effect of time, therefore no follow-up statistical tests were conducted. Changes in joint kinematics, tendon strain, velocity, work and power and muscle activity during the stance phase were assessed with 1D statistical parametric mapping, all of which also demonstrated a lack of change in response to the intervention. This in vivo examination of tendon function in walking provides an important foundation for investigating the functional consequences of training adaptations. We found substantial increases in AT stiffness did not impact on tendon function during walking. AT stiffness measured during walking, however, was unchanged with training, which suggests that increases in stiffness may not be evident across the whole force-elongation relation, a finding which may help explain previously mixed intervention results and guide future investigations in the functional implications of tendon adaptation.
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Petrovic, M., C. N. Maganaris, K. Deschamps, S. M. Verschueren, F. L. Bowling, A. J. M. Boulton, and N. D. Reeves. "Altered Achilles tendon function during walking in people with diabetic neuropathy: implications for metabolic energy saving." Journal of Applied Physiology 124, no. 5 (May 1, 2018): 1333–40. http://dx.doi.org/10.1152/japplphysiol.00290.2017.
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The Achilles tendon (AT) has the capacity to store and release elastic energy during walking, contributing to metabolic energy savings. In diabetes patients, it is hypothesized that a stiffer Achilles tendon may reduce the capacity for energy saving through this mechanism, thereby contributing to an increased metabolic cost of walking (CoW). The aim of this study was to investigate the effects of diabetes and diabetic peripheral neuropathy (DPN) on the Achilles tendon and plantarflexor muscle-tendon unit behavior during walking. Twenty-three nondiabetic controls (Ctrl); 20 diabetic patients without peripheral neuropathy (DM), and 13 patients with moderate/severe DPN underwent gait analysis using a motion analysis system, force plates, and ultrasound measurements of the gastrocnemius muscle, using a muscle model to determine Achilles tendon and muscle-tendon length changes. During walking, the DM and particularly the DPN group displayed significantly less Achilles tendon elongation (Ctrl: 1.81; DM: 1.66; and DPN: 1.54 cm), higher tendon stiffness (Ctrl: 210; DM: 231; and DPN: 240 N/mm), and higher tendon hysteresis (Ctrl: 18; DM: 21; and DPN: 24%) compared with controls. The muscle fascicles of the gastrocnemius underwent very small length changes in all groups during walking (~0.43 cm), with the smallest length changes in the DPN group. Achilles tendon forces were significantly lower in the diabetes groups compared with controls (Ctrl: 2666; DM: 2609; and DPN: 2150 N). The results strongly point toward the reduced energy saving capacity of the Achilles tendon during walking in diabetes patients as an important factor contributing to the increased metabolic CoW in these patients. NEW & NOTEWORTHY From measurements taken during walking we observed that the Achilles tendon in people with diabetes and particularly people with diabetic peripheral neuropathy was stiffer, was less elongated, and was subject to lower forces compared with controls without diabetes. These altered properties of the Achilles tendon in people with diabetes reduce the tendon’s energy saving capacity and contribute toward the higher metabolic energy cost of walking in these patients.
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Kovács, B., I. Kóbor, Ö. Sebestyén, and J. Tihanyi. "Longer Achilles tendon moment arm results in better running economy." Physiology International 107, no. 4 (January 12, 2021): 527–41. http://dx.doi.org/10.1556/2060.2020.10000.
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AbstractBased on the current literature, the link between Achilles tendon moment arm length and running economy is not well understood. Therefore, the aim of this study was to further investigate the connection between Achilles tendon moment arm and running economy and the influence of Achilles tendon moment arm on the function of the plantarflexor muscle-tendon unit during running.Ten male competitive marathon runners volunteered for this study. The participants ran on a treadmill at two running speeds: 3 and 3.5 m s−1. During running the oxygen consumption, lower leg kinematics, electrical activity of plantar flexor muscles, and fascicle behavior of the lateral gastrocnemius were measured simultaneously. On the second occasion, an MRI scan of the right leg was taken and used to estimate the Achilles tendon moment arm length.There was a negative correlation between running economy and the body height normalized moment arm length at both selected speeds (r = −0.68, P = 0.014 and r = −0.70, P = 0.01). In addition, Achilles tendon moment arm length correlated with the amplitude of the ankle flexion at both speeds (r = −0.59, P = 0.03 and r = −0.60, P = 0.03) and with the electrical activity of the medial gastrocnemius muscle at 3 m s−1 speed (r = −0.62, P = 0.02). Our finding supports the concept that a longer moment arm could be beneficial for distance runners.
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Jackson, Janna R., Michael J. Ryan, Yanlei Hao, and Stephen E. Alway. "Mediation of endogenous antioxidant enzymes and apoptotic signaling by resveratrol following muscle disuse in the gastrocnemius muscles of young and old rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 299, no. 6 (December 2010): R1572—R1581. http://dx.doi.org/10.1152/ajpregu.00489.2010.
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Hindlimb suspension (HLS) elicits muscle atrophy, oxidative stress, and apoptosis in skeletal muscle. Increases in oxidative stress can have detrimental effects on muscle mass and function, and it can potentially lead to myonuclear apoptosis. Resveratrol is a naturally occurring polyphenol possessing both antioxidant and antiaging properties. To analyze the capacity of resveratrol to attenuate oxidative stress, apoptosis and muscle force loss were measured following 14 days of HLS. Young (6 mo) and old (34 mo) rats were administered either 12.5 mg·kg−1·day−1 of trans-resveratrol, or 0.1% carboxymethylcellulose for 21 days, including 14 days of HLS. HLS induced a significant decrease in plantarflexor isometric force, but resveratrol blunted this loss in old animals. Resveratrol increased gastrocnemius catalase activity, MnSOD activity, and MnSOD protein content following HLS. Resveratrol reduced hydrogen peroxide and lipid peroxidation levels in muscles from old animals after HLS. Caspase 9 abundance was reduced and Bcl-2 was increased, but other apoptotic markers were not affected by resveratrol in the gastrocnemius muscle after HLS. The data indicate that resveratrol has a protective effect against oxidative stress and muscle force loss in old HLS animals; however, resveratrol was unable to attenuate apoptosis following HLS. These results suggest that resveratrol has the potential to be an effective therapeutic agent to treat muscle functional decrements via improving the redox status associated with disuse.
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Cinone, Nicoletta, Sara Letizia, Luigi Santoro, Salvatore Facciorusso, Raffaella Armiento, Alessandro Picelli, Maurizio Ranieri, and Andrea Santamato. "Combined Effects of Isokinetic Training and Botulinum Toxin Type A on Spastic Equinus Foot in Patients with Chronic Stroke: A Pilot, Single-blind, Randomized Controlled Trial." Toxins 11, no. 4 (April 8, 2019): 210. http://dx.doi.org/10.3390/toxins11040210.
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Botulinum toxin A (BoNT-A) has been shown effective for poststroke lower limb spasticity. Following injections, a wide range of multidisciplinary approach has been previously provided. The purpose of this pilot, single-blind, randomized controlled trial was to determine whether BoNT-A combined with a regime of a four-week ankle isokinetic treatment has a positive effect on function and spasticity, compared with BoNT-A alone. Secondly, the validity of the use of an isokinetic dynamometer to measure the stretch reflex at the ankle joint and residual strength has been investigated. Twenty-five chronic stroke patients were randomized to receive combined treatment (n = 12; experimental group) or BoNT-A alone (n = 13; control group). Outcome measures were based on the International Classification of Functioning, Disability and Health. An isokinetic dynamometer was also used for stretch reflex and strength assessment. Patients were evaluated at baseline (t0), after five (t1) and eight weeks after the injection (t2). The experimental group reported significantly greater improvements on lower limb spasticity, especially after eight weeks from baseline. Gait speed (10-m walk test) and walking capacity (6-min walking test) revealed statistically significantly better improvement in the experimental than in control group. Peak resistive ankle torque during growing angular velocities showed a significant reduction at the higher velocities after BoNT-A injections in the experimental group. Peak dorsiflexor torque was significantly increased in the experimental group and peak plantarflexor torque was significantly decreased in control group. Alternative rehabilitation strategies that combine BoNT-A and an intense ankle isokinetic treatment are effective in reducing tone and improving residual strength and motor function in patients with chronic hemiparesis.
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Paton, Joanne S., Katherine Thomason, Karl Trimble, James E. Metcalfe, and Jonathan Marsden. "Effect of a Forefoot Off-loading Postoperative Shoe on Muscle Activity, Posture, and Static Balance." Journal of the American Podiatric Medical Association 103, no. 1 (January 1, 2013): 36–42. http://dx.doi.org/10.7547/1030036.
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Background: We investigated whether a forefoot off-loading postoperative shoe (FOPS) alters standing posture, ankle muscle activity, and static postural sway and whether any effects are altered by wearing a shoe raise on the contralateral side. Methods: Posture, ankle muscle activity, and postural sway were compared in 14 healthy participants wearing either a FOPS or a control shoe with or without a contralateral shoe raise. Participants were tested under different sensory and support surface conditions. Additionally, reductions in peak pressure under the forefoot while walking were assessed with and without a contralateral shoe raise to determine whether the FOPS continued to achieve its primary off-loading function. Results: Compared with the control condition, wearing a FOPS moved the center of pressure posteriorly, increased tibialis anterior muscle activity, and reduced ankle plantarflexor activity. These changes decreased when a contralateral shoe raise was added. No difference in postural sway was found between footwear conditions. Forefoot peak pressure was always reduced when wearing the FOPS. Conclusions: The posterior shift in center of pressure toward and behind the ankle joint axis is believed to result in the increase in tibialis anterior muscle activity that now acts as the primary stabilizer around the ankle. Instability may, therefore, increase in patients with weak tibialis anterior muscles (eg, diabetic neuropathy) who need to wear offloading devices for ulcer management. We suggest that the addition of a contralateral shoe raise fitted with a FOPS may potentially be beneficial in maintaining stability while off-loading the forefoot in this patient group. (J Am Podiatr Med Assoc 103(1): 36–42, 2013)
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Wade, Francesca E., Gregory Lewis, Andrea H. Horne, Lauren Hickox, Michael C. Aynardi, Paul J. Juliano, Umur Aydogan, and Stephen J. Piazza. "Changes in the Plantarflexion Moment Arm of the Achilles Tendon Following Total Ankle Arthroplasty." Foot & Ankle Orthopaedics 5, no. 4 (October 1, 2020): 2473011420S0048. http://dx.doi.org/10.1177/2473011420s00480.
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Category: Ankle; Ankle Arthritis Introduction/Purpose: Deficits in ankle joint kinetics following total ankle arthroplasty (TAA) may be attributed to a reduction in the force-generating capacity of ankle joint muscles, but it is also important to consider the alterations to joint structure that may accompany this procedure. One key parameter indicative of joint structure with the potential to be influenced by TAA is the plantarflexion moment arm of the Achilles tendon (ATma). ATma is an indicator of the potential for the tendon force to produce plantarflexion moment that is determined by the three-dimensional line of action of the tendon relative to the ankle joint axis. The purpose of this study was to assess pre-to-post TAA changes in ATma; we hypothesized that pre- and post-TAA moment arms would not be different. Methods: We tested 10 TAA patients (age at surgery: 62.86 +- 9.72 y; height: 1.72 +- 0.08 m; body mass: 97.81 +- 20.89 kg) at pre-operative (˜ 1 mo pre) and post-operative (˜6 mo post) visits. All procedures involving testing of human subjects were approved by the Penn State Hershey Medical Center Institutional Review Board. ATma were measured using a method that combined ultrasound imaging of the tendon with 3D motion tracking of both the ultrasound probe and the ankle joint. The tendon and joint axis were located during trials in which the patients were seated with the knee extended while the ankle joint was voluntarily rotated in the sagittal plane. We also examined sagittal-plane weightbearing radiographs (pre- and post-op) to determine the AP distance from the center of the talar dome to the posterior margin of the calcaneus. Pre- and post-op ATma were compared using a paired t-test and regression. Results: No significant mean differences were found between post-op ATma and pre-op ATma (p = 0.360). Despite this, some patients were found to have large differences between pre- and postoperative ATma. For example, participants 1, 3, and 8 exhibited changes of -54.22%, +64.14% and +123.98% (pre-to-post) respectively (Figure 1). A moderate correlation between pre- and post-op ATma was found (r2 = 0.461, p = 0.031), indicating that only 46.1% of the variance in post-op ATma was explained by pre-op ATma (Figure 1). The normalized AP distance measured from the radiographs did not significantly change on average pre- to post-TAA (p = 0.561), and we found the change in this distance to correlate with the change in ATma (r2 = 0.370, p = 0.062). Conclusion: This is the first investigation of whether TAA alters ATma. Our results supported our hypothesis that pre-operative ATma predicts post-operative ATma. However, our hypothesis is supported only when the mean differences are considered, as there were sizeable differences for individuals. Despite a non-significant average change in ATma following TAA, at the individual level substantial changes in ATma were observed in seven of the 10 patients. Change in ATma was only partly explained by change in the AP position of the talar dome. Change in ATma has potential consequences for function in terms of ankle plantarflexor strength and walking velocity.
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Kanayama, Atsuki, Mayuka Minami, Saki Yamamoto, Toshimitsu Ohmine, Minami Fujiwara, Takayuki Murakami, Shuji Okuno, Ryoga Ueba, and Akira Iwata. "Examination of the Impact of Strength and Velocity of the Knee and Ankle on Gait Speed in Community-Dwelling Older Adults." Healthcare 10, no. 10 (October 20, 2022): 2093. http://dx.doi.org/10.3390/healthcare10102093.
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The muscle strength of the knee extension and plantarflexion plays a crucial role in determining gait speed. Recent studies have shown that no-load angular velocity of the lower limb joints is essential for determining gait speed. However, no reports have compared the extent to which lower limb functions, such as knee extension strength, knee extension velocity, plantarflexion strength, and plantarflexion velocity, impact gait speed in a single study. Therefore, this study aimed to examine the relative importance of maximum strength and no-load angular velocity on gait speed. Overall, 164 community-dwelling older adults (72.9 ± 5.0 years) participated in this study. We measured the gait speed and lower limb function (the strength and velocity of knee extension and plantarflexion). Strength was measured with a hand-held dynamometer, and velocity with a gyroscope. A multiple regression analysis was performed with gait speed as the dependent variable and age, sex, and lower-limb function as independent variables. Plantarflexion velocity (β = 0.25) and plantarflexion strength (β = 0.21) were noted to be significant predictors of gait speed. These findings indicate that no-load plantarflexion velocity is more important than the strength of plantarflexion and knee extensions as a determinant of gait speed, suggesting that improvement in plantarflexion velocity may increase gait speed.
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Tavara-Vidalón, Sandra, Manuel Monge-Vera, Guillermo Lafuente-Sotillos, Gabriel Domínguez-Maldonado, and Pedro Munuera-Martínez. "Static Range of Motion of the First Metatarsal in the Sagittal and Frontal Planes." Journal of Clinical Medicine 7, no. 11 (November 21, 2018): 456. http://dx.doi.org/10.3390/jcm7110456.
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The first metatarsal and medial cuneiform form an important functional unit in the foot, called “first ray”. The first ray normal range of motion (ROM) is difficult to quantify due to the number of joints that are involved. Several methods have previously been proposed. Controversy exists related to normal movement of the first ray frontal plane accompanying that in the sagittal plane. The objective of this study was to investigate the ROM of the first ray in the sagittal and frontal planes in normal feet. Anterior-posterior radiographs were done of the feet of 40 healthy participants with the first ray in a neutral position, maximally dorsiflexed and maximally plantarflexed. They were digitalized and the distance between the tibial malleolus and the intersesamoid crest in the three positions mentioned was measured. The rotation of the first ray in these three positions was measured. A polynomic function that fits a curve describing the movement observed in the first ray was obtained using the least squares method. ROM of the first ray in the sagittal plane was 6.47 (SD 2.59) mm of dorsiflexion and 6.12 (SD 2.55) mm of plantarflexion. ROM in the frontal plane was 2.69 (SD 4.03) degrees of inversion during the dorsiflexion and 2.97 (SD 2.72) degrees during the plantarflexion. A second-degree equation was obtained, which represents the movement of the first ray. Passive dorsiflexion and plantarflexion of the first ray were accompanied by movements in the frontal plane: 0.45 degrees of movement were produced in the frontal plane for each millimeter of displacement in the sagittal plane. These findings might be useful for the future design of instruments for clinically quantifying first ray mobility.
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Rowley, KM, Danielle N. Jarvis, Toshiyuki Kurihara, Yu-Jen Chang, Abbigail L. Fietzer, and Kornelia Kulig. "Toe Flexor Strength, Flexibility and Function and Flexor Hallucis Longus Tendon Morphology in Dancers and Non-Dancers." Medical Problems of Performing Artists 30, no. 3 (September 1, 2015): 152–56. http://dx.doi.org/10.21091/mppa.2015.3029.
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Tendinopathy of the flexor hallucis longus (FHL), colloquially referred to as “dancer’s tendinitis,” is a common condition in dancers and attributed to high demand on this muscle in positions of extreme ankle plantarflexion and metatarsophalangeal (MTP) flexion and extension. Despite such a high prevalence, there has been little research into preventative or nonsurgical interventions. As a means to identify potential targets for prevention and intervention, this study aimed to characterize toe flexors in dancers by measuring strength, flexibility, function, and FHL tendon morphology. Dancers (n=25) were compared to non-dancers (n=25) in toe flexor isometric strength, first MTP joint range of motion, foot longitudinal arch flexibility, balance ability, endurance during modified heel raises without use of the toes, and FHL tendon thickness, cross-sectional area, and peak spatial frequency. Significant differences were found in functional first MTP joint extension (dancers 101.95º, non-dancers 91.15º, p<0.001), balance ability during single-leg stance on the toes (dancers 11.43 s, non-dancers 5.90 s, p=0.013), and during modified heel raises (dancers 22.20 reps, non-dancers 28.80 reps, p=0.001). Findings indicate that dancers rely on toe flexors more than non-dancers to complete balance and heel raise tasks. Efficacy of using this modified heel raise task with the toes off the edge of a block as a means to train larger plantarflexors and as a nonsurgical intervention should be studied in the future. Improving interventions for FHL tendinopathy will be impactful for dancers, in whom this condition is highly prevalent.
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Böhm, Harald, Hösl Matthias, Frank Braatz, and Leonhard Döderlein. "Effect of floor reaction ankle–foot orthosis on crouch gait in patients with cerebral palsy: What can be expected?" Prosthetics and Orthotics International 42, no. 3 (July 11, 2017): 245–53. http://dx.doi.org/10.1177/0309364617716240.
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Background: Floor reaction ankle–foot orthoses are commonly prescribed to improve knee extension of children with cerebral palsy having crouch gait. Their effectiveness is debated. Therefore, the objective of this study is to optimize current prescription criteria for the improvement of crouch gait. Study design: Cross-sectional interventional study. Methods: A total of 22 patients with bilateral spastic cerebral palsy, between 6 and 17 years, Gross Motor Function Classification System II–IV participated in this study. Instrumented gait analysis was done under three conditions: barefoot, shoed, and with orthotics. Patients were divided into two groups: good and non-responders with more and less than 8.8° improvement of knee extension during walking, respectively. A multiple predictor analysis was done on parameters that were different between groups. Results: In total, 12 of 22 patients showed good response in knee extension with a mean change of 17° (standard deviation = 5°). Good responders showed a significantly smaller walking velocity, knee extension strength, ankle plantarflexion strength, and greater external foot progression angle compared to non-responders. Foot progression angle together with ankle plantarflexion strength explained 37% of the variance in improvement of knee extension. Conclusion: With appropriate patient selection, an improvement of crouch gait by ankle–foot orthoses of 17° (standard deviation = 5°) can be expected. Patients with slow velocity, weak plantarflexors, and external foot progression benefit most. Joint contractures were no contraindications. Clinical relevance This study showed that gait in patients with low functional level benefit most from ankle–foot orthoses. Unlike in patients with higher functional status, contractures of hip, knee, and ankle did not reduce the positive effects on gait. The suggested prescription criteria may help to better select appropriate patients for orthotics.
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MAGANARIS, CONSTANTINOS N. "EVIDENCE OF TIME-DEPENDENT TENSILE RESPONSE IN INTACT HUMAN TENDON." Journal of Mechanics in Medicine and Biology 04, no. 01 (March 2004): 61–69. http://dx.doi.org/10.1142/s0219519404000898.
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The present study was performed to establish whether intact human tendons exhibit time-dependent tensile properties, as they do in the in vitro state. Measurements were taken in seven men and involved ultrasound-based recording of the gastrocnemius tendon elongation during three sets of five repeated isometric plantarflexion contractions elicited by tetanic electrical stimulation. The plantarflexion moment corresponding to the tendon elongation in the fifth contraction presented a pattern dependent on the voltage applied: it was approximately constant when applying 50% of maximal voltage, but it decreased curvilinearly as a function of contraction number when applying 70 and 100% of maximal voltage, reaching in the fifth contraction 84% of the plantarflexion moment corresponding to the elongation examined in the first contraction. These results suggest that, once a threshold tendon elongation is undergone, in vivo tendons may exhibit substantial viscoelasticity. The present findings have implications for muscle and joint function and need to be accounted for by musculoskeletal models.
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Nikoo, Ali, and Thomas K. Uchida. "Be Careful What You Wish for: Cost Function Sensitivity in Predictive Simulations for Assistive Device Design." Symmetry 14, no. 12 (November 30, 2022): 2534. http://dx.doi.org/10.3390/sym14122534.
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Software packages that use optimization to predict the motion of dynamic systems are powerful tools for studying human movement. These “predictive simulations” are gaining popularity in parameter optimization studies for designing assistive devices such as exoskeletons. The cost function is a critical component of the optimization problem and can dramatically affect the solution. Many cost functions have been proposed that are biologically inspired and that produce reasonable solutions, but which may lead to different conclusions in some contexts. We used OpenSim Moco to generate predictive simulations of human walking using several cost functions, each of which produced a reasonable trajectory of the human model. We then augmented the model with motors that generated hip flexion, knee flexion, or ankle plantarflexion torques, and repeated the predictive simulations to determine the optimal motor torques. The model was assumed to be planar and bilaterally symmetric to reduce computation time. Peak torques varied from 41.3 to 79.0 N·m for the hip flexion motors, from 48.0 to 94.2 N·m for the knee flexion motors, and from 42.6 to 79.8 N·m for the ankle plantarflexion motors, which could have important design consequences. This study highlights the importance of evaluating the robustness of results from predictive simulations.
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Butler, A. J., G. Yue, and W. G. Darling. "Variations in soleus H-reflexes as a function of plantarflexion torque in man." Brain Research 632, no. 1-2 (December 1993): 95–104. http://dx.doi.org/10.1016/0006-8993(93)91143-g.
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Nigg, B. M., V. Fisher, T. L. Allinger, J. R. Ronsky, and J. R. Engsberg. "Range of Motion of the Foot as a Function of Age." Foot & Ankle 13, no. 6 (July 1992): 336–43. http://dx.doi.org/10.1177/107110079201300608.
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Movement of the foot is essential for human locomotion. The purpose of this paper was to quantify the range of motion of the foot as a function of age and to compare the rage of motion measurements for the foot in a laboratory coordinate system and a coordinate system fixed to the tibia. The measurements were taken in vivo using a range of motion instrument developed by Allinger (University of Calgary, Canada, 1990) from 121 subjects. The results suggest that: (1) the range of motion in general is greater for women than for men in the young adult group; (2) the range of motion in general is in the same order of magnitude for women and men in the oldest age group; and (3) the range of motion is about 8° smaller in dorsiflexion and about 8° higher in plantarflexion for women than for men in the oldest age group. It is speculated that physical activity and common shoe wear are factors influencing the age- and gender-dependent differences in range of motion. Furthermore, it has been shown that the range of motion values measured in a laboratory coordinate system and in a coordinate system fixed in the tibia are different in all directions except inversion. The differences in plantarflexion and dorsiflexion and inversion and eversion are relatively small. However, they are substantial for adduction and abduction. In all cases, the results were bigger for measurements in the laboratory coordinate system compared with the tibia coordinate system, because the movement of the lower leg was included in the measurements in the laboratory coordinate system. The data indicate that foot range of motion is different for women and men. Consequently, it is speculated that these differences may be related to possible overloading of the locomotor system, especially in sporting activities in which the loading of the foot is significant. The differences in the plantarflexion and dorsiflexion direction were assumed to influence the loading of the Achilles tendon, and it is suggested that some of the Achilles tendon problems may be predictable based on range of motion measurements.
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Gregersen, Martin G., Andreas Fagerhaug Dalen, Fredrik Nilsen, and Marius Molund. "The Anatomy and Function of the Individual Bands of the Deltoid Ligament—and Implications for Stability Assessment of SER Ankle Fractures." Foot & Ankle Orthopaedics 7, no. 2 (April 2022): 247301142211040. http://dx.doi.org/10.1177/24730114221104078.
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Background: Deltoid ligament injury occurs often with supination-external rotation (SER) ankle trauma. SER fibula fractures with concomitant deltoid ligament injury are considered unstable—requiring operative fixation. Recent studies have questioned this general practice with emphasis on better defining the medial side ankle ligamentous injury. The function of the individual bands of the deltoid ligament, and the interplay between them, are not fully understood. We undertook this study to develop a better understanding of these complex ligamentous structures and ultimately aid assessment and treatment choice of SER ankle fractures with concomitant deltoid ligament injuries. Methods: Ten fresh-frozen cadaveric foot and ankle specimens were studied. We identified the various ligament bands and did a functional analysis by assessment of ligament length and tension at predefined angles of ankle dorsi-plantarflexion combined with valgus/varus and rotation. The results were determined by manual evaluation with calipers and goniometers, manual stress, and direct visualization. Results: We recorded primarily 5 different bands of the deltoid ligament: the tibionavicular (TNL; 10/10) tibiospring (TSL; 9/10), tibiocalcaneal (TCL; 10/10), deep anterior tibiotalar (dATTL; 9/10), and deep posterior tibiotalar (dPTTL; 10/10) ligaments. The tibiospring ligament was tense in plantarflexion, while the tibiocalcaneal and deep posterior tibiotalar ligaments were tense in dorsiflexion. The superficial layer ligaments and the deep anterior tibiotalar ligament length and tension were largely affected by changes in varus/valgus and rotation. The deep posterior tibiotalar ligament length and tension was altered predominantly by changes in dorsi-plantarflexion; varus/valgus positioning had a minor effect on this band. Conclusions: We confirmed the finding of previous studies that dorsi-plantarflexion affects the tensile engagement of the separate ligament bands differently. Likewise, combined movements with varus/valgus and rotation seem to affect the separate ligament bands differently. Our results suggest that the TNL, TSL, and dATTL are at risk of injury, whereas the TCL and particularly the dPTTL are protected in the event of an SER-type ankle fracture mechanism of injury. Level of Evidence Level V, cadaveric study.
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S. Jamsandekar, Madhura, Vivek Dineshbhai Patel, Ashish J. Prabhakar, Charu Eapen, and Justin W. L. Keogh. "Ability of functional performance assessments to discriminate athletes with and without chronic ankle instability : a case-control study." PeerJ 10 (May 27, 2022): e13390. http://dx.doi.org/10.7717/peerj.13390.
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Background The decline in motor function associated with chronic ankle instability (CAI) can be assessed using Functional Performance tests. Ankle muscular strength, endurance and range of motion (ROM) has been assessed in previous studies but functional activities such as sprinting and change of direction are less well studied in athletes with CAI. Hence the aim of this study was to determine how sprint, change of direction, ankle isometric strength, endurance and ROM measures may be associated with discriminate athletes with and without CAI. Methods One hundred and six participants (CAI: n = 53 or no CAI: n = 53) provided informed consent to participate in this study. Participants performed three functional performance tests, (30-m sprint test, Modified Illinois change of direction test (MICODT)) and change of direction test. Range of motion for dorsiflexion was measured using weight bearing lunge test and inversion, eversion and plantarflexion using Saunders® digital inclinometer. Strength was assessed using Baseline® hand-held dynamometer for plantarflexors, dorsiflexors, invertors and evertors. Muscular endurance was assessed by single heel raise test and Modified single heel raise test. Between-group comparisons utilised Student’s t-test and Mann-Whitney U-tests, with a number of unique variable and multivariable binomial logistic regression performed to determine which performance measures may discriminate participants with CAI. Results The CAI participants performed significantly worse in the three functional performance tests as well as multiple measures of ankle ROM, isometric strength and muscular endurance (p < 0.008). While several measures of ROM (plantarflexion and dorsiflexion), strength (inversion and eversion) and both muscular endurance tests were significantly associated with CAI in the univariable analysis, the strongest association was the functional performance tests, especially MICDOT time (odds ratio (95% CI): 0.06 [0.02–0.17], sensitivity 94.3%, specificity 88.7%). Multivariable regression analyses indicated that performance across the functional performance tests were more strongly associated with CAI than any ankle ROM, muscular strength or endurance test. Further, the inclusion of the best ankle range of motion, strength or muscular endurance tests did not significantly improve upon the association of the MICDOT with CAI. Conclusions Chronic ankle instability in athletic populations appears to be highly associated with declines in functional performance and to a somewhat lesser extent, ankle range of motion, strength and muscle endurance measures. This may suggest that optimal rehabilitation for athletes with CAI may require a greater focus on improving sprinting speed and change of direction ability in the mid to latter stages of rehabilitation, with regular assessments of these functional performance tests necessary to guide the progression and overload of this training.
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Kishimoto, Kenzo C., Martin E. Héroux, Simon C. Gandevia, Jane E. Butler, and Joanna Diong. "Estimation of maximal muscle electromyographic activity from the relationship between muscle activity and voluntary activation." Journal of Applied Physiology 130, no. 5 (May 1, 2021): 1352–61. http://dx.doi.org/10.1152/japplphysiol.00557.2020.
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Muscle activity is often normalized to maximal muscle activity; however, it is difficult to obtain accurate measures of maximal muscle activity in people with impaired voluntary neural drive. We determined the relationship between voluntary muscle activation and plantarflexor muscle activity across a broad range of muscle activation values in able-bodied people. The relationship between voluntary muscle activation and muscle activity can be described with simple mathematical functions capable of estimating maximal muscle activity.
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Armitano-Lago, Cortney, Hunter J. Bennett, and Justin A. Haegele. "Lower Limb Proprioception and Strength Differences Between Adolescents With Autism Spectrum Disorder and Neurotypical Controls." Perceptual and Motor Skills 128, no. 5 (August 2, 2021): 2132–47. http://dx.doi.org/10.1177/00315125211036418.
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Autism spectrum disorder (ASD) is a complex diagnosis characterized primarily by persistent deficits in social communication/interaction and repetitive behavior patterns, interests, and/or activities. ASD is also characterized by various physiological and/or behavioral features that span sensory, neurological, and neuromotor function. Although problems with lower body coordination and control have been noted, little prior research has examined lower extremity strength and proprioception, a process requiring integration of sensorimotor information to locate body/limbs in space. We designed this study to compare lower limb proprioception and strength in adolescents with ASD and neurotypical controls. Adolescents diagnosed with ASD (n = 17) and matched controls (n = 17) performed ankle plantarflexion/dorsiflexion bilateral proprioception and strength tests on an isokinetic dynamometer. We assessed position-based proprioception using three targeted positions (5 and 20-degrees plantarflexion and 10-degrees dorsiflexion) and speed-based proprioception using two targeted speeds (60 and 120-degrees/second). We assessed strength at 60-degrees/second. Participants with ASD performed 1.3-times more poorly during plantarflexion position and 2-times more poorly during the speed-based proprioception tests compared to controls. Participants with ASD also exhibited a 40% reduction in plantarflexion strength compared to controls. These findings provide insight into mechanisms that underly the reduced coordination, aberrant gait mechanics, and coordination problems often seen in individuals with ASD, and the identification of these mechanisms now permits better targeting of rehabilitative goals in treatment programs.