Articoli di riviste: "Human locomotion"

1

Hughes, J. "Human Locomotion". International Journal of Rehabilitation Research 8 (settembre 1985): 60. http://dx.doi.org/10.1097/00004356-198509001-00107.

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Minetti, Alberto. "Human locomotion". Journal of Biomechanics 40 (gennaio 2007): S4. http://dx.doi.org/10.1016/s0021-9290(07)70004-0.

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Oldenborg, Per-Arne, e Janove Sehlin. "The Glucose Concentration Modulates N-Formyl-Methionyl-Leucyl-Phenylalanine (fMet-Leu-Phe)-Stimulated Chemokinesis in Normal Human Neutrophils". Bioscience Reports 19, n. 6 (1 dicembre 1999): 511–23. http://dx.doi.org/10.1023/a:1020286010551.

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The effects of glucose concentration on the chemokinetic effects of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) was evaluated for normal human neutrophils using a direct microscopic assay. fMet-Leu-Phe increased the rate of locomotion in the absence of glucose, but the chemokinetic effect of fMet-Leu-Phe was most potent at 5mM glucose and not further changed at 15 mM glucose. The chemokinetic effects of fMet-Leu-Phe and glucose were essentially the same in blood clot-isolated and gradient-isolated neutrophils. However, in gradient-isolated neutrophils, the rate of locomotion under different experimental conditions was strictly negatively correlated to the fraction of non-locomoting cells and the degree of adhesion to the substratum. These results indicate that the chemokinetic effects of fMet-Leu-Phe are regulated by the glucose concentration by inducing locomotor activity in otherwise non-locomoting cells and by improving adhesion to the substratum.

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Yokoyama, Hikaru, Tetsuya Ogawa, Masahiro Shinya, Noritaka Kawashima e Kimitaka Nakazawa. "Speed dependency in α-motoneuron activity and locomotor modules in human locomotion: indirect evidence for phylogenetically conserved spinal circuits". Proceedings of the Royal Society B: Biological Sciences 284, n. 1851 (29 marzo 2017): 20170290. http://dx.doi.org/10.1098/rspb.2017.0290.

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Coordinated locomotor muscle activity is generated by the spinal central pattern generators (CPGs). Vertebrate studies have demonstrated the following two characteristics of the speed control mechanisms of the spinal CPGs: (i) rostral segment activation is indispensable for achieving high-speed locomotion; and (ii) specific combinations between spinal interneuronal modules and motoneuron (MN) pools are sequentially activated with increasing speed. Here, to investigate whether similar control mechanisms exist in humans, we examined spinal neural activity during varied-speed locomotion by mapping the distribution of MN activity in the spinal cord and extracting locomotor modules, which generate basic MN activation patterns. The MN activation patterns and the locomotor modules were analysed from multi-muscle electromyographic recordings. The reconstructed MN activity patterns were divided into the following three patterns depending on the speed of locomotion: slow walking, fast walking and running. During these three activation patterns, the proportion of the activity in rostral segments to that in caudal segments increased as locomotion speed increased. Additionally, the different MN activation patterns were generated by distinct combinations of locomotor modules. These results are consistent with the speed control mechanisms observed in vertebrates, suggesting phylogenetically conserved spinal mechanisms of neural control of locomotion.

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Friedl, P., P. B. Noble e K. S. Zänker. "T lymphocyte locomotion in a three-dimensional collagen matrix. Expression and function of cell adhesion molecules." Journal of Immunology 154, n. 10 (15 maggio 1995): 4973–85. http://dx.doi.org/10.4049/jimmunol.154.10.4973.

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Abstract T cell locomotion within the extracellular matrix may be mediated by cell adhesion molecules. We investigated the expression and function of beta 1- and beta 2-integrins and CD44 on human peripheral CD4+ and CD8+ lymphocytes locomoting in a 3-D type I collagen matrix. Paths of randomly selected T cells were digitized from time-lapse videorecordings and were quantitatively analyzed. After the blocking of CD49b with mAb Gi9, the locomotion of a defined locomotor subset (50% of spontaneously locomoting cells) was inhibited. Anti-CD49d mAb HP2/1 and an activating anti-CD44 mAb (J173), respectively, induced transient recruitment (< 1 h) of previously nonmotile cells (10 to 35%). In contrast to the J173-induced short-term locomotion, hyaluronan incorporated within the matrix promoted locomotion for > 2 h. No significant effects were present for anti-CD49f (GoH3) and -CD11a (25.3) mAbs. After the addition of IL-8 to the matrix, rapid induction of locomotion in 20 to 30% of the cells (control) was evident, which was virtually abolished by anti-alpha 2- and alpha 6-integrin, and -CD11a mAbs. Thus, the locomotion of nonactivated and IL-8-activated T cells may involve different sets of integrins. Using flow cytometry, the development of a CD49b+CD29highCD44lowL-selectinlow T cell phenotype independent of activation markers including CD25, CD27, CD28, VLA-4, and CD45RA- to CD45RO-transition was observed after 4 days in the matrix. The initial development of spontaneous locomotion in the collagen matrix, however, was not accompanied by alterations in CAM surface staining and, therefore, may involve functional CAM activation rather than involving an increase in surface expression.

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Glasheen, J. W., e T. A. McMahon. "Arms are different from legs: mechanics and energetics of human hand-running". Journal of Applied Physiology 78, n. 4 (1 aprile 1995): 1280–87. http://dx.doi.org/10.1152/jappl.1995.78.4.1280.

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To determine whether nonlocomotor limbs (arms) differ from locomotor limbs (legs), we trained human subjects to run on their hands while supporting a fraction of their body weight. We wanted to know whether the low cost of force production and the speed-independent limb stiffness of locomotor limbs were characteristics associated with locomotion or were inherent properties of all limbs. We found that the limb stiffness of the human arm increases by 135% over less than a fourfold range in peak vertical force. In contrast, human legs and a variety of other mammalian locomotor limbs maintain a constant stiffness, regardless of speed and loading, for normal running. In addition, we explored the energetics of locomotion in hand-running. The economy of force generation (in J/N) is invariant with speed, as is found in legged locomotion. However, our results show that the metabolic cost of force generation while running on human arms is four to five times greater than the cost of force generation for the locomotor limbs of running quadrupeds.

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Olds, Tim. "Modelling Human Locomotion". Sports Medicine 31, n. 7 (2001): 497–509. http://dx.doi.org/10.2165/00007256-200131070-00005.

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Mille, Marie-Laure, Martin Simoneau e Mark W. Rogers. "Postural dependence of human locomotion during gait initiation". Journal of Neurophysiology 112, n. 12 (15 dicembre 2014): 3095–103. http://dx.doi.org/10.1152/jn.00436.2014.

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The initiation of human walking involves postural motor actions for body orientation and balance stabilization that must be effectively integrated with locomotion to allow safe and efficient transport. Our ability to coordinately adapt these functions to environmental or bodily changes through error-based motor learning is essential to effective performance. Predictive compensations for postural perturbations through anticipatory postural adjustments (APAs) that stabilize mediolateral (ML) standing balance normally precede and accompany stepping. The temporal sequencing between these events may involve neural processes that suppress stepping until the expected stability conditions are achieved. If so, then an unexpected perturbation that disrupts the ML APAs should delay locomotion. This study investigated how the central nervous system (CNS) adapts posture and locomotion to perturbations of ML standing balance. Healthy human adults initiated locomotion while a resistance force was applied at the pelvis to perturb posture. In experiment 1, using random perturbations, step onset timing was delayed relative to the APA onset indicating that locomotion was withheld until expected stability conditions occurred. Furthermore, stepping parameters were adapted with the APAs indicating that motor prediction of the consequences of the postural changes likely modified the step motor command. In experiment 2, repetitive postural perturbations induced sustained locomotor aftereffects in some parameters (i.e., step height), immediate but rapidly readapted aftereffects in others, or had no aftereffects. These results indicated both rapid but transient reactive adaptations in the posture and gait assembly and more durable practice-dependent changes suggesting feedforward adaptation of locomotion in response to the prevailing postural conditions.

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Behrman, Andrea L., e Susan J. Harkema. "Locomotor Training After Human Spinal Cord Injury: A Series of Case Studies". Physical Therapy 80, n. 7 (1 luglio 2000): 688–700. http://dx.doi.org/10.1093/ptj/80.7.688.

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AbstractMany individuals with spinal cord injury (SCI) do not regain their ability to walk, even though it is a primary goal of rehabilitation. Mammals with thoracic spinal cord transection can relearn to step with their hind limbs on a treadmill when trained with sensory input associated with stepping. If humans have similar neural mechanisms for locomotion, then providing comparable training may promote locomotor recovery after SCI. We used locomotor training designed to provide sensory information associated with locomotion to improve stepping and walking in adults after SCI. Four adults with SCIs, with a mean postinjury time of 6 months, received locomotor training. Based on the American Spinal Injury Association (ASIA) Impairment Scale and neurological classification standards, subject 1 had a T5 injury classified as ASIA A, subject 2 had a T5 injury classified as ASIA C, subject 3 had a C6 injury classified as ASIA D, and subject 4 had a T9 injury classified as ASIA D. All subjects improved their stepping on a treadmill. One subject achieved overground walking, and 2 subjects improved their overground walking. Locomotor training using the response of the human spinal cord to sensory information related to locomotion may improve the potential recovery of walking after SCI.

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Minassian, Karen, Ursula S. Hofstoetter, Florin Dzeladini, Pierre A. Guertin e Auke Ijspeert. "The Human Central Pattern Generator for Locomotion: Does It Exist and Contribute to Walking?" Neuroscientist 23, n. 6 (28 marzo 2017): 649–63. http://dx.doi.org/10.1177/1073858417699790.

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The ability of dedicated spinal circuits, referred to as central pattern generators (CPGs), to produce the basic rhythm and neural activation patterns underlying locomotion can be demonstrated under specific experimental conditions in reduced animal preparations. The existence of CPGs in humans is a matter of debate. Equally elusive is the contribution of CPGs to normal bipedal locomotion. To address these points, we focus on human studies that utilized spinal cord stimulation or pharmacological neuromodulation to generate rhythmic activity in individuals with spinal cord injury, and on neuromechanical modeling of human locomotion. In the absence of volitional motor control and step-specific sensory feedback, the human lumbar spinal cord can produce rhythmic muscle activation patterns that closely resemble CPG-induced neural activity of the isolated animal spinal cord. In this sense, CPGs in humans can be defined by the activity they produce. During normal locomotion, CPGs could contribute to the activation patterns during specific phases of the step cycle and simplify supraspinal control of step cycle frequency as a feedforward component to achieve a targeted speed. Determining how the human CPGs operate will be essential to advance the theory of neural control of locomotion and develop new locomotor neurorehabilitation paradigms.

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FERRIS, DANIEL P., GREGORY S. SAWICKI e MONICA A. DALEY. "A PHYSIOLOGIST'S PERSPECTIVE ON ROBOTIC EXOSKELETONS FOR HUMAN LOCOMOTION". International Journal of Humanoid Robotics 04, n. 03 (settembre 2007): 507–28. http://dx.doi.org/10.1142/s0219843607001138.

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Technological advances in robotic hardware and software have enabled powered exoskeletons to move from science fiction to the real world. The objective of this article is to emphasize two main points for future research. First, the design of future devices could be improved by exploiting biomechanical principles of animal locomotion. Two goals in exoskeleton research could particularly benefit from additional physiological perspective: (i) reduction in the metabolic energy expenditure of the user while wearing the device, and (ii) minimization of the power requirements for actuating the exoskeleton. Second, a reciprocal potential exists for robotic exoskeletons to advance our understanding of human locomotor physiology. Experimental data from humans walking and running with robotic exoskeletons could provide important insight into the metabolic cost of locomotion that is impossible to gain with other methods. Given the mutual benefits of collaboration, it is imperative that engineers and physiologists work together in future studies on robotic exoskeletons for human locomotion.

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Lacquaniti, Francesco, Yuri P. Ivanenko e Myrka Zago. "Development of human locomotion". Current Opinion in Neurobiology 22, n. 5 (ottobre 2012): 822–28. http://dx.doi.org/10.1016/j.conb.2012.03.012.

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Kawashima, Noritaka, Daichi Nozaki, Masaki O. Abe e Kimitaka Nakazawa. "Shaping Appropriate Locomotive Motor Output Through Interlimb Neural Pathway Within Spinal Cord in Humans". Journal of Neurophysiology 99, n. 6 (giugno 2008): 2946–55. http://dx.doi.org/10.1152/jn.00020.2008.

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Direct evidence supporting the contribution of upper limb motion on the generation of locomotive motor output in humans is still limited. Here, we aimed to examine the effect of upper limb motion on locomotor-like muscle activities in the lower limb in persons with spinal cord injury (SCI). By imposing passive locomotion-like leg movements, all cervical incomplete ( n = 7) and thoracic complete SCI subjects ( n = 5) exhibited locomotor-like muscle activity in their paralyzed soleus muscles. Upper limb movements in thoracic complete SCI subjects did not affect the electromyographic (EMG) pattern of the muscle activities. This is quite natural since neural connections in the spinal cord between regions controlling upper and lower limbs were completely lost in these subjects. On the other hand, in cervical incomplete SCI subjects, in whom such neural connections were at least partially preserved, the locomotor-like muscle activity was significantly affected by passively imposed upper limb movements. Specifically, the upper limb movements generally increased the soleus EMG activity during the backward swing phase, which corresponds to the stance phase in normal gait. Although some subjects showed a reduction of the EMG magnitude when arm motion was imposed, this was still consistent with locomotor-like motor output because the reduction of the EMG occurred during the forward swing phase corresponding to the swing phase. The present results indicate that the neural signal induced by the upper limb movements contributes not merely to enhance but also to shape the lower limb locomotive motor output, possibly through interlimb neural pathways. Such neural interaction between upper and lower limb motions could be an underlying neural mechanism of human bipedal locomotion.

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Korivand, Soroush, Nader Jalili e Jiaqi Gong. "Inertia-Constrained Reinforcement Learning to Enhance Human Motor Control Modeling". Sensors 23, n. 5 (1 marzo 2023): 2698. http://dx.doi.org/10.3390/s23052698.

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Locomotor impairment is a highly prevalent and significant source of disability and significantly impacts the quality of life of a large portion of the population. Despite decades of research on human locomotion, challenges remain in simulating human movement to study the features of musculoskeletal drivers and clinical conditions. Most recent efforts to utilize reinforcement learning (RL) techniques are promising in the simulation of human locomotion and reveal musculoskeletal drives. However, these simulations often fail to mimic natural human locomotion because most reinforcement strategies have yet to consider any reference data regarding human movement. To address these challenges, in this study, we designed a reward function based on the trajectory optimization rewards (TOR) and bio-inspired rewards, which includes the rewards obtained from reference motion data captured by a single Inertial Moment Unit (IMU) sensor. The sensor was equipped on the participants’ pelvis to capture reference motion data. We also adapted the reward function by leveraging previous research on walking simulations for TOR. The experimental results showed that the simulated agents with the modified reward function performed better in mimicking the collected IMU data from participants, which means that the simulated human locomotion was more realistic. As a bio-inspired defined cost, IMU data enhanced the agent’s capacity to converge during the training process. As a result, the models’ convergence was faster than those developed without reference motion data. Consequently, human locomotion can be simulated more quickly and in a broader range of environments, with a better simulation performance.

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Ko, Hyeongseok, e James Cremer. "VRLOCO: Real-Time Human Locomotion from Positional Input Streams". Presence: Teleoperators and Virtual Environments 5, n. 4 (gennaio 1996): 367–80. http://dx.doi.org/10.1162/pres.1996.5.4.367.

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Virtual reality applications, especially in entertainment and training, require environments populated with multiple interacting humans. Whether the virtual humans are controlled by real people or by computer programs, a large portion of their activity will involve locomotion. This paper presents VRLOCO, a “locomotion engine” designed to meet the locomotion requirements of virtual environments. First, VRLOCO is broadly capable; it includes five locomotion primitives—walking, running, lateral stepping, turning around, and backward stepping—and can blend smoothly between primitives during transitions. Second, locomotion control in VRLOCO is simple; controllers drive the locomotion by supplying streams of intuitive positional inputs—desired body center position and facing direction—over time. Finally, VRLOCO is responsive and efficient; it generates locomotion on-line, processing user- or program-generated control inputs and producing new frames at rates greater than 30 Hz. Technically, VRLOCO combines a method for generalizing prototypical locomotion data with algorithms for determining locomotion mode and blending between different modes. The effectiveness of the approach has been tested using several locomotion controllers—programs representing autonomous agents, interactive graphic user interfaces, and a VR input device consisting of a stationary bicycle equipped with optical encoders and a microcontroller.

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Zelik, Karl E., Valentina La Scaleia, Yuri P. Ivanenko e Francesco Lacquaniti. "Can modular strategies simplify neural control of multidirectional human locomotion?" Journal of Neurophysiology 111, n. 8 (15 aprile 2014): 1686–702. http://dx.doi.org/10.1152/jn.00776.2013.

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Each human lower limb contains over 50 muscles that are coordinated during locomotion. It has been hypothesized that the nervous system simplifies muscle control through modularity, using neural patterns to activate muscles in groups called synergies. Here we investigate how simple modular controllers based on invariant neural primitives (synergies or patterns) might generate muscle activity observed during multidirectional locomotion. We extracted neural primitives from unilateral electromyographic recordings of 25 lower limb muscles during five locomotor tasks: walking forward, backward, leftward and rightward, and stepping in place. A subset of subjects also performed five variations of forward (unidirectional) walking: self-selected cadence, fast cadence, slow cadence, tiptoe, and uphill (20% incline). We assessed the results in the context of dimensionality reduction, defined here as the number of neural signals needing to be controlled. For an individual task, we found that modular architectures could theoretically reduce dimensionality compared with independent muscle control, but we also found that modular strategies relying on neural primitives shared across different tasks were limited in their ability to account for muscle activations during multi- and unidirectional locomotion. The utility of shared primitives may thus depend on whether they can be adapted for specific task demands, for instance, by means of sensory feedback or by being embedded within a more complex sensorimotor controller. Our findings indicate the need for more sophisticated formulations of modular control or alternative motor control hypotheses in order to understand muscle coordination during locomotion.

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Takahashi, Kota Z., Rebecca L. Krupenevich, Amy L. Lenz, Luke A. Kelly, Michael J. Rainbow e Jason R. Franz. "Mechanics and Energetics of Human Feet: A Contemporary Perspective for Understanding Mobility Impairments in Older Adults". Biomechanics 2, n. 4 (23 settembre 2022): 494–99. http://dx.doi.org/10.3390/biomechanics2040038.

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Much of our current understanding of age-related declines in mobility has been aided by decades of investigations on the role of muscle–tendon units spanning major lower extremity joints (e.g., hip, knee and ankle) for powering locomotion. Yet, mechanical contributions from foot structures are often neglected. This is despite the emerging evidence of their critical importance in youthful locomotion. With the rapid growth in the field of human foot biomechanics over the last decade, our theoretical knowledge of young asymptomatic feet has transformed, from long-held views of the foot as a stiff lever and a shock absorber to that of a versatile system that can modulate mechanical power and energy output to accommodate various locomotor task demands. In this perspective review, we predict that the next set of impactful discoveries related to locomotion in older adults will emerge by integrating the novel tools and approaches that are currently transforming the field of human foot biomechanics. By illuminating the functions of the feet in older adults, we envision that future investigations will refine our mechanistic understanding of mobility deficits affecting our aging population, which may ultimately inspire targeted interventions to rejuvenate the mechanics and energetics of locomotion.

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Silva, Alessandro Brugnera, Marc Murcia, Omid Mohseni, Ryu Takahashi, Arturo Forner-Cordero, Andre Seyfarth, Koh Hosoda e Maziar Ahmad Sharbafi. "Design of Low-Cost Modular Bio-Inspired Electric–Pneumatic Actuator (EPA)-Driven Legged Robots". Biomimetics 9, n. 3 (7 marzo 2024): 164. http://dx.doi.org/10.3390/biomimetics9030164.

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Exploring the fundamental mechanisms of locomotion extends beyond mere simulation and modeling. It necessitates the utilization of physical test benches to validate hypotheses regarding real-world applications of locomotion. This study introduces cost-effective modular robotic platforms designed specifically for investigating the intricacies of locomotion and control strategies. Expanding upon our prior research in electric–pneumatic actuation (EPA), we present the mechanical and electrical designs of the latest developments in the EPA robot series. These include EPA Jumper, a human-sized segmented monoped robot, and its extension EPA Walker, a human-sized bipedal robot. Both replicate the human weight and inertia distributions, featuring co-actuation through electrical motors and pneumatic artificial muscles. These low-cost modular platforms, with considerations for degrees of freedom and redundant actuation, (1) provide opportunities to study different locomotor subfunctions—stance, swing, and balance; (2) help investigate the role of actuation schemes in tasks such as hopping and walking; and (3) allow testing hypotheses regarding biological locomotors in real-world physical test benches.

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Chettibi, S., A. J. Lawrence, J. D. Young, P. D. Lawrence e R. D. Stevenson. "Dispersive locomotion of human neutrophils in response to a steroid-induced factor from monocytes". Journal of Cell Science 107, n. 11 (1 novembre 1994): 3173–81. http://dx.doi.org/10.1242/jcs.107.11.3173.

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A monocyte-derived factor that stimulates the locomotion of human neutrophils on an albumin-coated glass surface has been prepared from the culture supernatant of dexamethasone-treated human monocytes and called STMS (steroid-treated monocyte supernatant). A modified cell tracking program has been developed and the parameters of locomotion determined by the analysis of Gail and Boone for cells moving in a persistent random walk. Cells moving in uniform concentrations of STMS, interleukin-8 (IL-8) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) chosen to give a sub-maximal speed of locomotion show persistent, random and constrained random diffusion, respectively, with augmented diffusion coefficients of 0.8 +/- 0.1, 0.14 +/- 0.02 and 0.12 +/- 0.03 microns 2 per second for STMS, IL-8 and fMLP, respectively. The augmented diffusion coefficient and the underlying persistence are therefore sensitive quantitative assay parameters for STMS activity and the qualitative characteristics of locomotion allow STMS activity to be distinguished from that of all other factors tested. The contribution of lowered adhesion to locomotion was examined in a novel tilt-assay, which demonstrated that cells in the presence of STMS, but not other factors, moved down slope with significantly increased speed while maintaining contact with the substratum. The results were interpreted in terms of the bipolar form of STMS-treated cells, contrasting with multipolar forms in response to other agents. This together with low adhesiveness plus an inherent tendency of a single locomotor focus to continue motion in its original direction has been used to explain the difference between response to STMS and other factors.(ABSTRACT TRUNCATED AT 250 WORDS)

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Niemitz, Carsten. "Kinematics and ontogeny of locomotion in monkeys and human babies". Zeitschrift für Morphologie und Anthropologie 83, n. 2-3 (25 aprile 2002): 383–400. http://dx.doi.org/10.1127/zma/83/2002/383.

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Lacquaniti, Francesco, Yuri P. Ivanenko e Myrka Zago. "Patterned control of human locomotion". Journal of Physiology 590, n. 10 (11 aprile 2012): 2189–99. http://dx.doi.org/10.1113/jphysiol.2011.215137.

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Devine, John. "The Versatility of Human Locomotion". American Anthropologist 87, n. 3 (settembre 1985): 550–70. http://dx.doi.org/10.1525/aa.1985.87.3.02a00030.

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Mather, George, e Rebecca Sharman. "Adaptation to human locomotion speed". Journal of Vision 16, n. 12 (1 settembre 2016): 397. http://dx.doi.org/10.1167/16.12.397.

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Woodley, David T., John D. Chen, Janice P. Kim, Yves Sarret, Toshiroh Iwasaki, Youn H. Kim e Edward J. O’Keefe. "Re-Epithelialization: Human Keratinocyte Locomotion". Dermatologic Clinics 11, n. 4 (ottobre 1993): 641–46. http://dx.doi.org/10.1016/s0733-8635(18)30217-1.

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Warren, William H., e Brett R. Fajen. "Behavioral Dynamics of Human Locomotion". Ecological Psychology 16, n. 1 (gennaio 2004): 61–66. http://dx.doi.org/10.1207/s15326969eco1601_8.

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Hultborn, Hans. "Neurobiological basis of human locomotion". Trends in Neurosciences 15, n. 8 (agosto 1992): 310. http://dx.doi.org/10.1016/0166-2236(92)90084-l.

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Bernardin, Delphine, Hideki Kadone, Daniel Bennequin, Thomas Sugar, Mohamed Zaoui e Alain Berthoz. "Gaze anticipation during human locomotion". Experimental Brain Research 223, n. 1 (12 settembre 2012): 65–78. http://dx.doi.org/10.1007/s00221-012-3241-2.

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Borghese, N. A., L. Bianchi e F. Lacquaniti. "Kinematic determinants of human locomotion." Journal of Physiology 494, n. 3 (1 agosto 1996): 863–79. http://dx.doi.org/10.1113/jphysiol.1996.sp021539.

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Bing, Chu Yih, S.Parasuraman e M. K. A. Ahmed Khan. "Electromyography (EMG) and Human Locomotion". Procedia Engineering 41 (2012): 486–92. http://dx.doi.org/10.1016/j.proeng.2012.07.202.

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Ayyappa, Ed. "Normal Human Locomotion, Part 1". JPO Journal of Prosthetics and Orthotics 9, n. 1 (1997): 10???17. http://dx.doi.org/10.1097/00008526-199700910-00004.

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Ayyappa, Edmond. "Normal Human Locomotion, Part 2". JPO Journal of Prosthetics and Orthotics 9, n. 2 (1997): 49???57. http://dx.doi.org/10.1097/00008526-199700920-00004.

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Ayyappa, Edmond. "Normal Human Locomotion, Part 2". JPO Journal of Prosthetics and Orthotics 9, n. 2 (1997): 49???57. http://dx.doi.org/10.1097/00008526-199704000-00003.

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Ayyappa, Ed. "Normal Human Locomotion, Part 1". JPO Journal of Prosthetics and Orthotics 9, n. 1 (1997): 10???17. http://dx.doi.org/10.1097/00008526-199710000-00004.

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Alexander, R. McNeill. "Simple Models of Human Locomotion". Journal of Theoretical Medicine 1, n. 2 (1997): 129–35. http://dx.doi.org/10.1080/10273669708833013.

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Abstract (sommario):

The human body is a complex structure, but our understanding of its movements is greately enhanced by extremely simple mathematical models. A model of walking shows why we have to break into a run at speeds above 3 meters per second, and why the critical speed is lower for children and on the moon. A model of running jumps show why long jumpers run up at a fast sprinting speed, but high jumpers run up much more slowly. Finally, a model od standing jumps explains why athletes can jump higher by using a countermovement than from a static squatting position. The body is represented in these models as a small number of rigid segments connected by hinge joints, powered by muscles with realistic physiological properties.

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Alexander, R. Mc Neill. "Simple models of human locomotion". Computational and Mathematical Methods in Medicine 2, n. 1 (1999): 129–35. http://dx.doi.org/10.1080/10273669908833034.

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Wilkinson, P. C., J. M. Lackie, W. S. Haston e L. N. Islam. "Effects of phorbol esters on shape and locomotion of human blood lymphocytes". Journal of Cell Science 90, n. 4 (1 agosto 1988): 645–55. http://dx.doi.org/10.1242/jcs.90.4.645.

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The effects of phorbol esters on shape change and locomotion of human blood lymphocytes were studied both immediately after separating the cells from blood and after overnight culture. Phorbol myristate acetate (PMA), phorbol dibutyrate (PDB) and related esters produced complex shape changes in lymphocytes at both times. These shapes were analysed quantitatively using objective measurements derived from the moments of cell shapes. Immediately after removal from blood, many lymphocytes (20–60% of the total) protruded and retracted veils or spikes at more than one point on the cell surface. The morphology of these cells was not typical of locomotor cells. Usually, formation of a veil was not followed by a contraction wave moving down the cell, though some cells did show contraction waves, and some moved into collagen gels or filters. After overnight culture, a high proportion (70–80%) of cells had changed shape in PMA and PDB. Although the shapes were still atypical, they resembled classical locomotor morphology more closely; veils formed at one point on the cell surface tended to persist, and contraction waves and constriction rings were seen in many cells. These cells moved in large numbers into collagen gels or filters. Comparison of the paths traversed by PMA-treated lymphocytes in collagen gels suggested that cells cultured in PMA for 24 h pursued more persistent paths that those in short-term culture, but the difference was not marked. We suggest that phorbol esters induce immediate shape change without inducing the complete sequence of motor events necessary for efficient locomotion, whereas after prolonged culture in phorbol esters, locomotion is more efficient, possibly because phorbol esters, like other growth activators, stimulate events during the G1 phase of growth that are necessary for full expression of locomotor capacity.

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37

MacKay-Lyons, Marilyn. "Central Pattern Generation of Locomotion: A Review of the Evidence". Physical Therapy 82, n. 1 (1 gennaio 2002): 69–83. http://dx.doi.org/10.1093/ptj/82.1.69.

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Abstract Neural networks in the spinal cord, referred to as “central pattern generators” (CPGs), are capable of producing rhythmic movements, such as swimming, walking, and hopping, even when isolated from the brain and sensory inputs. This article reviews the evidence for CPGs governing locomotion and addresses other factors, including supraspinal, sensory, and neuromodulatory influences, that interact with CPGs to shape the final motor output. Supraspinal inputs play a major role not only in initiating locomotion but also in adapting the locomotor pattern to environmental and motivational conditions. Sensory afferents involved in muscle and cutaneous reflexes have important regulatory functions in preserving balance and ensuring stable phase transitions in the locomotor cycle. Neuromodulators evoke changes in cellular and synaptic properties of CPG neurons, conferring flexibility to CPG circuits. Briefly addressed is the interaction of CPG networks to produce intersegmental coordination for locomotion. Evidence for CPGs in humans is reviewed, and although a comprehensive clinical review is not an objective, examples are provided of animal and human studies that apply knowledge of CPG mechanisms to improve locomotion. The final section deals with future directions in CPG research.

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38

Knikou, Maria. "Plasticity of Corticospinal Neural Control after Locomotor Training in Human Spinal Cord Injury". Neural Plasticity 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/254948.

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Spinal lesions substantially impair ambulation, occur generally in young and otherwise healthy individuals, and result in devastating effects on quality of life. Restoration of locomotion after damage to the spinal cord is challenging because axons of the damaged neurons do not regenerate spontaneously. Body-weight-supported treadmill training (BWSTT) is a therapeutic approach in which a person with a spinal cord injury (SCI) steps on a motorized treadmill while some body weight is removed through an upper body harness. BWSTT improves temporal gait parameters, muscle activation patterns, and clinical outcome measures in persons with SCI. These changes are likely the result of reorganization that occurs simultaneously in supraspinal and spinal cord neural circuits. This paper will focus on the cortical control of human locomotion and motor output, spinal reflex circuits, and spinal interneuronal circuits and how corticospinal control is reorganized after locomotor training in people with SCI. Based on neurophysiological studies, it is apparent that corticospinal plasticity is involved in restoration of locomotion after training. However, the neural mechanisms underlying restoration of lost voluntary motor function are not well understood and translational neuroscience research is needed so patient-orientated rehabilitation protocols to be developed.

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Ryczko, Dimitri, Jackson J. Cone, Michael H. Alpert, Laurent Goetz, François Auclair, Catherine Dubé, Martin Parent, Mitchell F. Roitman, Simon Alford e Réjean Dubuc. "A descending dopamine pathway conserved from basal vertebrates to mammals". Proceedings of the National Academy of Sciences 113, n. 17 (11 aprile 2016): E2440—E2449. http://dx.doi.org/10.1073/pnas.1600684113.

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Dopamine neurons are classically known to modulate locomotion indirectly through ascending projections to the basal ganglia that project down to brainstem locomotor networks. Their loss in Parkinson’s disease is devastating. In lampreys, we recently showed that brainstem networks also receive direct descending dopaminergic inputs that potentiate locomotor output. Here, we provide evidence that this descending dopaminergic pathway is conserved to higher vertebrates, including mammals. In salamanders, dopamine neurons projecting to the striatum or brainstem locomotor networks were partly intermingled. Stimulation of the dopaminergic region evoked dopamine release in brainstem locomotor networks and concurrent reticulospinal activity. In rats, some dopamine neurons projecting to the striatum also innervated the pedunculopontine nucleus, a known locomotor center, and stimulation of the dopaminergic region evoked pedunculopontine dopamine release in vivo. Finally, we found dopaminergic fibers in the human pedunculopontine nucleus. The conservation of a descending dopaminergic pathway across vertebrates warrants re-evaluating dopamine’s role in locomotion.

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40

Sylos-Labini, Francesca, Francesco Lacquaniti e Yuri P. Ivanenko. "Human Locomotion under Reduced Gravity Conditions: Biomechanical and Neurophysiological Considerations". BioMed Research International 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/547242.

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Reduced gravity offers unique opportunities to study motor behavior. This paper aims at providing a review on current issues of the known tools and techniques used for hypogravity simulation and their effects on human locomotion. Walking and running rely on the limb oscillatory mechanics, and one way to change its dynamic properties is to modify the level of gravity. Gravity has a strong effect on the optimal rate of limb oscillations, optimal walking speed, and muscle activity patterns, and gait transitions occur smoothly and at slower speeds at lower gravity levels. Altered center of mass movements and interplay between stance and swing leg dynamics may challenge new forms of locomotion in a heterogravity environment. Furthermore, observations in the lack of gravity effects help to reveal the intrinsic properties of locomotor pattern generators and make evident facilitation of nonvoluntary limb stepping. In view of that, space neurosciences research has participated in the development of new technologies that can be used as an effective tool for gait rehabilitation.

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Hay, James G. "Cycle Rate, Length, and Speed of Progression in Human Locomotion". Journal of Applied Biomechanics 18, n. 3 (agosto 2002): 257–70. http://dx.doi.org/10.1123/jab.18.3.257.

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There have been few attempts to synthesize the knowledge gleaned from the study of cyclic human locomotion and, specifically, to determine whether there are general laws that describe or govern all such forms of locomotion. The purpose of this paper was to test the hypothesis that, when a human participant performs multiple trials of a given form of cyclic locomotion at a wide range of speeds (S) and without constraint on cycle rate (CR) or cycle length (CL), the relationships of CR vs. S and CL vs. S have the same basic characteristics as do those for any other form of cyclic locomotion. Data were gathered from published and unpublished sources. For each participant and form of locomotion, CR-vs.-S and CL-vs.-S relationships were plotted on a common scattergram with S on the abscissa and both CR and CL on the ordinate. Analysis of data collected on 49 participants and 12 forms of locomotion showed that, for every combination of participant and form of locomotion considered (excluding combinations involving simulated locomotion), the relationships of CR vs. S and CL vs. S had the same basic characteristics. These relationships were quadratic in form with CR-vs.-S concave upward and CL-vs.-S concave downward. The factor that made the greater contribution to increases in S was a function of S, with CL the primary factor at low S and CR the primary factor at high S. In short, the results obtained provided unequivocal support for the hypothesis of the study. The basic CR-vs.-S and CL-vs.-S relationships observed for forms of actual locomotion were also observed for some, but not all, of the forms of simulated locomotion examined.

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Neal Webb, Sarah, e Steven Schapiro. "Locomotion as a Measure of Well-Being in Captive Chimpanzees (Pan troglodytes)". Animals 13, n. 5 (23 febbraio 2023): 803. http://dx.doi.org/10.3390/ani13050803.

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Locomotion in non-human primates, including walking, climbing, and brachiating among other types of movement (but not pacing), is a species-typical behavior that varies with age, social housing conditions, and environmental factors (e.g., season, food availability, physical housing conditions). Given that captive primates are typically observed to engage in lower levels of locomotor behaviors than their wild counterparts, increases in locomotion are generally considered to be indicative of improved welfare in captivity. However, increases in locomotion do not always occur with improvements in welfare, and sometimes occur under conditions of negative arousal. The use of time spent in locomotion as a welfare indicator in studies of well-being is relatively limited. We conducted focal animal observations on 120 captive chimpanzees across a series of studies and found higher percentages of time spent in locomotion (1) upon transfer to a new enclosure type, (2) in larger groups with wider within-group age ranges, and fewer males, and (3) with participation in an experimental medication choice paradigm. We also found that, among geriatric chimpanzees, those housed in nongeriatric groups exhibited more locomotion than those living in geriatric groups. Lastly, locomotion was significantly negatively correlated with several indicators of poor welfare and significantly positively correlated with behavioral diversity, one indicator of positive welfare. Overall, the increases in time spent in locomotion observed in these studies were part of an overall behavioral pattern indicative of enhanced welfare, suggesting that an increase in time spent in locomotion itself may be an indicator of enhanced welfare. As such, we suggest that levels of locomotion, which are typically assessed in most behavioral experiments, may be used more explicitly as indicators of welfare in chimpanzees.

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43

Kim, Yejin, e Myunggyu Kim. "Data-Driven Approach for Human Locomotion Generation". International Journal of Image and Graphics 15, n. 02 (aprile 2015): 1540001. http://dx.doi.org/10.1142/s021946781540001x.

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This paper introduces a data-driven approach for human locomotion generation that takes as input a set of example locomotion clips and a motion path specified by an animator. Significantly, the approach only requires a single example of straight-path locomotion for each style expressed and can produce a continuous output sequence on an arbitrary path. Our approach considers quantitative and qualitative aspects of motion and suggests several techniques to synthesize a convincing output animation: motion path generation, interactive editing, and physical enhancement for the output animation. Initiated with an example clip, this process produces motion that differs stylistically from any in the example set, yet preserves the high quality of the example motion. As shown in the experimental results, our approach provides efficient locomotion generation by editing motion capture clips, especially for a novice animator, at interactive speed.

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Klarner, Taryn, e E. Paul Zehr. "Sherlock Holmes and the curious case of the human locomotor central pattern generator". Journal of Neurophysiology 120, n. 1 (1 luglio 2018): 53–77. http://dx.doi.org/10.1152/jn.00554.2017.

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Evidence first described in reduced animal models over 100 years ago led to deductions about the control of locomotion through spinal locomotor central pattern-generating (CPG) networks. These discoveries in nature were contemporaneous with another form of deductive reasoning found in popular culture, that of Arthur Conan Doyle’s detective, Sherlock Holmes. Because the invasive methods used in reduced nonhuman animal preparations are not amenable to study in humans, we are left instead with deducing from other measures and observations. Using the deductive reasoning approach of Sherlock Holmes as a metaphor for framing research into human CPGs, we speculate and weigh the evidence that should be observable in humans based on knowledge from other species. This review summarizes indirect inference to assess “observable evidence” of pattern-generating activity that leads to the logical deduction of CPG contributions to arm and leg activity during locomotion in humans. The question of where a CPG may be housed in the human nervous system remains incompletely resolved at this time. Ongoing understanding, elaboration, and application of functioning locomotor CPGs in humans is important for gait rehabilitation strategies in those with neurological injuries.

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MacDougall, Hamish G., e Steven T. Moore. "Marching to the beat of the same drummer: the spontaneous tempo of human locomotion". Journal of Applied Physiology 99, n. 3 (settembre 2005): 1164–73. http://dx.doi.org/10.1152/japplphysiol.00138.2005.

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Laboratory studies have suggested that the preferred cadence of walking is ∼120 steps/min, and the vertical acceleration of the head exhibits a dominant peak at this step frequency (2 Hz). These studies have been limited to short periods of walking along a predetermined path or on a treadmill, and whether such a highly tuned frequency of movement can be generalized to all forms of locomotion in a natural setting is unknown. The aim of this study was to determine whether humans exhibit a preferred cadence during extended periods of uninhibited locomotor activity and whether this step frequency is consistent with that observed in laboratory studies. Head linear acceleration was measured over a 10-h period in 20 subjects during the course of a day, which encompassed a broad range of locomotor (walking, running, cycling) and nonlocomotor (working at a desk, driving a car, riding a bus or subway) activities. Here we show a highly tuned resonant frequency of human locomotion at 2 Hz (SD 0.13) with no evidence of correlation with gender, age, height, weight, or body mass index. This frequency did not differ significantly from the preferred step frequency observed in the seminal laboratory study of Murray et al. (Murray MP, Drought AB, and Kory RC. J Bone Joint Surg 46A: 335–360, 1964). [1.95 Hz (SD 0.19)]. On the basis of the frequency characteristics of otolith-spinal reflexes, which drive lower body movement via the lateral vestibulospinal tract, and otolith-mediated collic and ocular reflexes that maintain gaze when walking, we speculate that this spontaneous tempo of locomotion represents some form of central “resonant frequency” of human movement.

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Boletsis, Costas, e Jarl Erik Cedergren. "VR Locomotion in the New Era of Virtual Reality: An Empirical Comparison of Prevalent Techniques". Advances in Human-Computer Interaction 2019 (1 aprile 2019): 1–15. http://dx.doi.org/10.1155/2019/7420781.

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The latest technical and interaction advancements within the virtual reality (VR) field have marked a new era, not only for VR, but also for VR locomotion. In this era, well-established, prevalent VR locomotion techniques are mostly used as points of comparison for benchmarking of new VR locomotion designs. At the same time, there is the need for more exploratory, comparative studies of contemporary VR locomotion techniques, so that their distinguished interaction aspects can be documented and guide the design process of new techniques. This article presents a comparative, empirical evaluation study of contemporary and prevalent VR locomotion techniques, examining the user experience (UX) they offer. First, the prevalent VR locomotion techniques are identified based on literature, i.e., walking-in-place, controller/joystick, and teleportation. Twenty-six adults are enrolled in the study and perform a game-like task using the techniques. The study follows a mixed methods approach, utilising the System Usability Scale survey, the Game Experience Questionnaire, and a semistructured interview to assess user experiences. Results indicate that the walking-in-place technique offers the highest immersion but also presents high levels of psychophysical discomfort. Controller/joystick VR locomotion is perceived as easy-to-use due to the users’ familiarity with controllers, whereas teleportation is considered to be effective due to its fast navigation, although its visual ‘jumps’ do break the users’ sense of immersion. Based on the interviews, the users focused on the following interaction dimensions to describe their VR locomotion experiences: (i) immersion and flow, (ii) ease-of-use and mastering, (iii) competence and sense of effectiveness, and (iv) psychophysical discomfort. The study implications for VR locomotion are discussed, along with the study limitations and the future direction for research.

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Entschladen, F., B. Niggemann, K. S. Zänker e P. Friedl. "Differential requirement of protein tyrosine kinases and protein kinase C in the regulation of T cell locomotion in three-dimensional collagen matrices." Journal of Immunology 159, n. 7 (1 ottobre 1997): 3203–10. http://dx.doi.org/10.4049/jimmunol.159.7.3203.

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Abstract Locomotion of T lymphocytes within three-dimensional collagen matrices is regulated via different signaling states of the cells. Purified human CD4+ and CD8+ T cells developed a spontaneously locomoting subpopulation of about 25% of the whole population immediately after incorporation into a three-dimensional collagen matrix analyzed by time-lapse videomicroscopy. This spontaneous locomotion was accompanied by enhanced tyrosine phosphorylation of the focal adhesion kinase (FAK). Inhibition of protein tyrosine kinase (PTK) activity using genistein significantly reduced the spontaneous locomotory activity. This reduction was overcome by subsequent activation of protein kinase C (PKC) using PMA, which led to a persistent increase of locomotory activity to more than 60% of the cells. Thus, the PKC-driven type of locomotion was independent of PTK activity, whereas spontaneous locomotion was not altered by inhibition of PKC activity using calphostin C or inhibition of the serine/ threonine phosphatases pp1 and pp2A using okadaic acid. We presume that PTK activity, especially tyrosine phosphorylation of FAK, is decisively involved in the regulation of spontaneous T lymphocyte locomotion, which is independent of PKC activity. In contrast, PKC-driven locomotion is independent of tyrosine phosphorylation events, indicating that T lymphocyte locomotion is regulated by more than one signal transduction pathway. Furthermore, confocal microscopy analysis of phosphotyrosine residues, FAK, and PKC revealed an exclusive cellular distribution of these components, suggesting a regulation of T lymphocyte locomotion different from migration models developed for other cell types, which refer to a colocalization of FAK and PKC in focal adhesions.

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Kido, Aiko, Naofumi Tanaka e Richard B. Stein. "Spinal reciprocal inhibition in human locomotion". Journal of Applied Physiology 96, n. 5 (maggio 2004): 1969–77. http://dx.doi.org/10.1152/japplphysiol.01060.2003.

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The purpose of this paper was to study spinal inhibition during several different motor tasks in healthy human subjects. The short-latency, reciprocal inhibitory pathways from the common peroneal (CP) nerve to the soleus muscle and from the tibial nerve to the tibialis anterior muscle were studied as a depression of ongoing voluntary electromyograph (EMG) activity. First, the effect of stimulus intensity on the amount of inhibition was examined to decide an appropriate stimulation to study the task-dependent modulation of inhibition. Then, the inhibition at one level of stimulation (1.5 × motor threshold) was investigated during standing, walking, and running. The change in slope of inhibition vs. EMG level, which approximates the fraction of ongoing activity that is inhibited, decreased with CP stimulation from 0.52 during standing to 0.30 during fast walking (6 km/h) to 0.17 during running at 9 km/h. Similarly, the slope decreased with tibial nerve stimulation from 0.68 (standing) to 0.42 (fast walking) to 0.35 (running at 9 km/h). All differences, except the last one, were highly significant ( P < 0.01, Student's t-test). However, the difference between walking (0.42) and running (0.36) at the same speed (6 km/h) was not significant with tibial nerve stimulation and only significant at P < 0.05 with CP nerve stimulation (0.30, 0.20). Also, the difference between standing (0.52) and slow walking (3 km/h; 0.41) with CP stimulation was not significant, but it was significant ( P < 0.01) with tibial nerve stimulation (0.68, 0.49). In conclusion, our findings indicate that spinal reciprocal inhibition decreases substantially with increasing speed and only changes to a lesser extent with task.

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Gervasio, Sabata, Dario Farina, Thomas Sinkjær e Natalie Mrachacz-Kersting. "Crossed reflex reversal during human locomotion". Journal of Neurophysiology 109, n. 9 (1 maggio 2013): 2335–44. http://dx.doi.org/10.1152/jn.01086.2012.

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During human walking, precise coordination between the two legs is required in order to react promptly to any sudden hazard that could threaten stability. The networks involved in this coordination are not yet completely known, but a direct spinal connection between soleus (SOL) muscles has recently been revealed. For this response to be functional, as previously suggested, we hypothesize that it will be accompanied by a reaction in synergistic muscles, such as gastrocnemius lateralis (GL), and that a reversal of the response would occur when an opposite reaction is required. In the present study, surface EMGs of contralateral SOL and GL were analyzed after tibial nerve (TN), sural nerve (SuN), and medial plantar nerve (MpN) stimulation during two tasks in which opposite reactions are functionally expected: normal walking (NW), just before ipsilateral heel strike, and hybrid walking (HW) (legs walking in opposite directions), at ipsilateral push off and contralateral touchdown. Early crossed facilitations were observed in the contralateral GL after TN stimulation during NW, and a reversal of such responses occurred during HW. These results underline the functional significance of short-latency crossed responses and represent the first evidence for short-latency reflex reversal in the contralateral limb for humans. Muscle afferents seem to mediate the response during NW, while during HW cutaneous afferents are likely involved. It is thus possible that different afferents mediate the crossed response during different tasks.

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Masumoto, Kenji, e John A. Mercer. "Biomechanics of Human Locomotion in Water". Exercise and Sport Sciences Reviews 36, n. 3 (luglio 2008): 160–69. http://dx.doi.org/10.1097/jes.0b013e31817bfe73.

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