Literatura académica sobre el tema "Exercise Intolerance, Older adults, Young, Strength"

The objectives of these studies were to 1) evaluate the relationships among age, glucose intolerance, and skeletal muscle capillary basement membrane (CBM) width (CBMW) and 2) determine the effects of exercise training on CBMW by comparing values of young (28 +/- 4 yr) and older (63 +/- 7 yr) athletes with those of age-matched sedentary control subjects and by measuring CBMW in older men and women before and after a 9-mo endurance-exercise training program. CBMW was measured in tissue samples obtained from the gastrocnemius muscle. CBMW in sedentary 64 +/- 3-yr-old subjects was 25% thicker than in sedentary 24 +/- 3-yr-old subjects. CBMW was similar in young and older athletes and was thinner than the CBMW of age-matched sedentary control subjects. There were no differences in CBMW among older sedentary individuals with normal or impaired glucose tolerance or mild non-insulin-dependent diabetes mellitus. Nine months of endurance exercise training reduced CBMW in older men and women by 30-40%, to widths that were not different from those of the young subjects; this response was independent of glucose tolerance status. These findings suggest that habitual exercise prevents the thickening of the skeletal muscle CBM that is characteristic of advancing age. Moreover, the thickening of the CBM appears to be readily reversed as a result of exercise training, even in older individuals.

Morphological studies have reported fewer muscle fibers in older men suggesting fewer motor units and therefore more force absorbed per muscle fiber. Physiologic studies concur with this information, reporting decreases in lean body mass and muscular strength, and lower levels of fitness (i.e. aerobic capacity) in older subjects. Muscle specimens taken from older adults have shown a greater occurance of non specific ultrastructural alterations, including Z disk thickening, myofibrillar focal damage, and lipufuscin granules. These findings suggest that skeletal muscle of older adults may be more susceptible to environmental stress and may not regenerate as effectively following trauma. Our laboratory has investigated the ultrastructure of thigh muscle in young adults following an exercise scheme designed to stress muscle during lengthening (i.e. eccentric exercise) and result in muscle damage. The vulnerability of the ultrastructure of older adults to exercise induced muscle damage has not been investigated. The purpose of this study is to compare the frequency of occurance of non specific myofibrillar disturbances in young and older adults, and describe the fine structure of skeletal muscle of older adults prior to, immediately following, and at a time when muscle regeneration is expected to occur.

The link between age-related changes in muscle strength and gait is unclear. We tested if knee extensor functional demand differs by age and physical activity status and if functional demand increases with walking speed or after exercise. Gait and knee extensor muscle torque were collected from young adults and highly and less active older adults before and after treadmill walking. Functional demand was the ratio of knee moments during gait to knee extensor muscle torques estimated from participant-specific torque–velocity curves. Functional demand at the peak knee flexion moment was greater in less active older adults than young adults (29.3% [14.3%] vs 24.6% [12.1%]) and increased with walking speed (32.0% [13.9%] vs 22.8% [10.4%]). Functional demand at both knee extension moments increased ∼2% to 3% after exercise. The low functional demand found in this study suggests that healthy adults maintain a reserve of knee extensor strength.

This study compared muscle adaptations after 7 days of exercise with eccentric-overload (EO) or standard (ST) resistive training in young (20 years) and older (69 years) adults. Young EO and ST gained 103 and 30 N, respectively, and older EO and ST gained 63 and 25 N of strength, respectively (all p < .05). Types I and IIa MHC mRNA levels were not altered, but Type IIx levels decreased 31% and 63% after the first and seventh exercise bouts, respectively, in young and decreased 30% after the seventh bout in older participants (all p < 05), independent of loading type. Type 11a fiber increased. Type IIx decreased, and Type IIa increased in both age groups independent of loading type (all p < 05). Electron microscopy revealed no myofibrillar disruption in young or older muscle. These data suggest that short-term EO produces larger strength gains than does ST without muscle-cell disruption or loading-type-specific changes in MHC mRNA isoforms in young and older skeletal muscle.

Age-related reductions in muscle strength and muscle power can have significant adverse effects on functional performance in older adults. Exercise training has been shown to be a potent stimulus for improvements in strength and power. However, investigation into how to best optimize training-related adaptations, as well as the accessibility of training methods, is needed. Traditional (TR) methods using gravity-dependent free-weights or weight machines can improve and maintain strength and power but are limited in their ability to provide constant muscle tension and high levels of muscle activation throughout the lowering (eccentric) phase of lifting. Eccentric overload (EO) training may overcome these limitations and has been shown to result in potent adaptations in both young and older adults. Methods of producing EO are significantly limited from a practical perspective. The addition of whole-body flywheel training equipment provides a practical method of producing EO and may be appropriate for older adults wanting to optimize training outcomes. Our review provides limited evidence of the use of eccentric overload flywheel training as a novel training method in seniors. Through the review of literature, EO training overcame some of the limitations set forth by traditional resistance training and demonstrated to have key benefits when combating age-related changes affecting muscle strength and muscle power. It can be concluded that EO training is an important addition to the training arsenal for older adults. Flywheel training provides a practical method of achieving EO, increasing strength and power, combating age-related adaptations, and overall improving quality of life in older adults.

Abstract Bedrest is associated with cardiovascular and cerebrovascular changes that are linked to a greater prevalence of orthostatic intolerance; however, much of what we know from bedrest trials comes from young adults. How older adults respond to extended periods of activity restriction is not well understood. The current work tested the hypothesis that impaired control of cerebral blood flow in older adults following bedrest could be attenuated by regular exercise. Twenty-two older adults (55-65 years, 11 women) participated in a randomized controlled trial involving 14 days of continuous 6-degree head-down bedrest. The cohort was randomized to an exercise intervention (EX), involving daily aerobic, high-intensity interval, and resistance training, or a control group (CON), involving passive manual therapy. Cerebral blood flow velocity, cardiac output, and arterial blood pressure were measured continuously during a passive 80-degree head-up tilt protocol for up to 15 minutes. Responses in the cerebral and peripheral vascular beds were quantified by vascular resistance (cerebral: resistance area product (RAP); peripheral: total peripheral resistance (TPR)). Following bedrest, both supine RAP and TPR were elevated (p&lt; 0.01), with no effect of exercise training. In addition, the number of participants who could not complete 15 minutes of tilt increased from 3 to 15 (8 EX, 7 CON). In these non-finishers, RAP dropped ~20% and TPR dropped ~15% during the final 2 minutes of tilt, with no difference between groups. These data suggest that multimodal exercise training is insufficient to prevent changes in cardiovascular and cerebrovascular regulation in older adults observed during 14-day bedrest.

PURPOSE: This study aimed to develop prediction equations for estimating the physical fitness age (PFA) of Korean adults in young (19-40 years), middle (41-64 years), and old (65-80 years) age groups.METHODS: Data from 122,842 individuals who participated in Korea National Physical Fitness Survey and National Fitness 100 from 2009 to 2014 were collected. Body composition, muscular strength, muscular endurance, flexibility, cardiorespiratory endurance, agility, power, balance, and coordination were measured. Pearson’s correlation and stepwise regression analyses were used to analyze the data.RESULTS: The equations were as follows: PFA for young males=22.321 −.088 (20-m PACER)+.317 (body mass index [BMI]); PFA for young females=24.486 −.143 (20-m PACER)+.304 (BMI); PFA for middle-aged males=66.644 −.044 (standing long jump) −.069 (20-m PACER) – .201 (weight) −.075 (modified sit-ups)+.269 (10-m shuttle run)+.320 (BMI); PFA for middle-aged females=66.814 −.098 (standing long jump) −.113 (modified sit-ups); PFA for older males=84.795+.093 (figure-of-8 walk) −.100 (chair standing) −.122 (weight) −.102 (relative grip strength) −.060 (sit-and-reach)+.147 (3-m up-and-go); and PFA for older females=80.577+.097 (figureof-8 walk)+.306 (3-m up-and-go) −.280 (weight) −.088 (relative grip strength) −.069 (sit-and-reach)+.393 (BMI) −.088 (chair standing) −.011 (2-min step-in-place).CONCLUSIONS: Our prediction equations for PFA can be used as a tool to prescribe sex- and age-appropriate exercise program and to verify the effect of the application of the exercise program by comparing pre -and post-PFA.

Human aging is associated with a significant reduction in muscle mass (sarcopenia) resulting in muscle weakness and functional limitations in the elderly. Sarcopenia has been associated with mitochondrial dysfunction and the accumulation of mtDNA deletions. Resistance training increases muscle strength and size and can increase mitochondrial capacity and decrease oxidative stress in older adults. Creatine monohydrate (CrM) and conjugated linoleic acid (CLA) have biological effects that could enhance some of the beneficial effects of resistance training in older adults (i.e., ↑ fat-free mass, ↓ total body fat). We have completed two resistance-training studies with CrM alone and CrM + CLA supplementation in older adults to evaluate the independent effects of exercise and dietary supplements, as well as their interactive effects. Our studies, and several others, have found that CrM enhanced the resistance exercise mediated gains in fat-free mass and strength. More recently, we found that the addition of CLA also lead to a significant reduction of body fat after six months of resistance training in older adults. Older adults have fewer wild-type mtDNA copies and higher amounts of mtDNA deletions as compared with younger adults in mature skeletal muscle; however, these deletions are not seen in the satellite cell-derived myoblast cultures. These findings, and the fact that mtDNA deletions are lower and wild-type mtDNA copy number is higher after resistance training in older adults, suggests that activation of satellite cells secondary to resistance exercise-induced muscle damage can dilute or “shift” the proportion of mtDNA genotype towards that of a younger adult. Recent evidence suggests that CrM supplementation in combination with strength training can enhance satellite cell activation and total myonuclei number per muscle fiber in young men. Future studies are required to determine whether the mitochondrial adaptations to resistance exercise in older adults are further enhanced with CrM supplementation and whether this is due to increased recruitment of satellite cells. It will also be important to determine whether these changes are maintained over a longer time period.

Abstract Bed rest is associated with increased risk of orthostatic intolerance on return to upright posture and, at least in young adults, regular exercise during bed rest is proposed as protective. 22 older adults (55-65 years, half women) participated in a randomized trial with 14-days of continuous 6-degree head-down bed rest. Half completed 60 min/day of aerobic and high-intensity interval cycling plus resistance exercises (Ex) while the other half were control (Con). A passive 80-degree head-up tilt (HUT) to a maximum of 15-min assessed orthostatic tolerance while cardio- and cerebrovascular responses were monitored to a pre-syncopal level of systolic blood pressure &lt; 90 mmHg. In pre-bed rest baseline, all but 3 women (Ex) completed 15-min HUT. After 14-days bed rest, only 3 men (1 Ex) and 1 woman (Ex) completed 15-min with no differences in tolerance between men and women or Ex and Con. Vasovagal syncope presented in 5 participants (2 M-Con, 1 M-Ex, 1 F-Con, 1 F-Ex), most other non-finishers had progressive reduction in stroke volume without adequate vasoconstriction. Reductions in cerebral blood velocity measured during HUT by Doppler ultrasound revealed strong linear relationships to both end-tidal PCO2 and mean arterial pressure across all participants. These data indicate that neither older men nor older women were protected from orthostatic intolerance by 60-min per day exercise including high-intensity interval training. These data contrast with previous findings in younger adults in controlled trials of bed rest pointing to the need for greater understanding of mechanisms regulating blood pressure and brain blood flow.

Researchers have alluded to the existence of "neural factors" in the expression and development of muscular strength. Candidate neural factors including motor unit recruitment, rate coding, doublet firing, and motor unit synchronization are discussed in this review. Aging is generally accompanied by lower motor unit discharge rates. However, both young and older adults exhibit rapid changes in muscular strength with repeated strength testing. These strength changes occur with concomitant albeit transient increases in motor unit discharge rate. These and other neural factors may contribute to the initial increases in muscular strength observed during the early phases of resistance exercise training. Key words: firing rate, muscle, exercise

Increase exercise efficiency is essential to sustain independently, effectively and at adequate speed the daily movement tasks and to acquire the dose-dependant health benefits of an active lifestyle. Exercise tolerance can be regarded relevant for exercise prescription and sport performance both. In older people strength training intervention can be therefore considered the only mode of training, regardless oxidative metabolism effects, because is dose adapted and has low contraindication for untrained/ low fitness people. Purpose: test the hypothesis that a strength intervention will reduce the magnitude of the excessVO2 and the VO2SC in young and in older healthy adults . Methods: 16 young adults subjects and 21 older adults were recruited to participate in a randomized controlled trail, splitted in two groups and involved in a 4-weeks strength training. Force was measured during both a 1RM field test on squat and deadlift and, olnly for the young adults, during a maximal isometric laboratory test (IS) on a force platform . Oxygen consumption was measured in a ramp incremental test (modelled using a double-linear fit) and in tri-replicate during a CWR exercise performed at ∆50 (50% of the difference between the first ventilator threshold and the maximal oxygen consumption) (VO2 was modelled using a bi-exponential equation and the magnitude of the VO2SC quantified pre and post intervention). Young adults and older adults groups were compared using a two-way (time, group) analysis of variance. Results: the ability to produce force increased significantly in the strength-training group for both young and older adults 1RM (and IS test in the young adults), whereas no significant changes were observed in the control group (p > 0.05). In the young adults during the RI exercise, a significant excess VO2 (ml∙min-1) was present before training in the intervention group (∆CI around the mean difference [0.73, 5.15], d = 1.5, p = 0.02). This difference disappeared after strength training (∆CI [-2.96, 2.97], d = 0.01, p = 0.99). In the older adults no excess VO2 (ml∙min-1) was present before (∆CI [-0.87, 3.03], d = -0,08, p = 0.24). After training older adults presented an excess VO2 (ml∙min-1) (∆CI [-0.48, 4.28], d = -0,7, p = 0.02). In addiction ∆VO2/∆PO slope2 was significantly decreased (∆= 20%, p=0.004). Before training all young adults subjects exhibited a significant slow component (d = 3.05, p = 0.001, 95% CI [0.37, 0.88]). After training a significant reduction of the VO2SC (ml∙min-1) was observed in the intervention group (∆CI [-606, -351], d = -4.01, p = 0.001) with no difference detected for the control group (∆CI [-220, 145], d = -0.21, p = 0.68). The VO2SC reduction in the training group was associated with a 74±56% (8±5 min) increase in the time to reach exhaustion while no comparable gain was detected in the control group (3±17% or 0.5±2 min). In older adults VO2SC (ml∙min-1) was present before training ( in both training and control group) After training was observed a significant slow component for both training (∆CI [0.02, 0.93], d = 0.32, p = 0.001) and control group (∆CI [-2, -0.77], d = -0.4, p = 0.31). The older adults training group was associated with a increase 32±67% , 6±3 min in time to teach exsaustion. Conclusions: In agreement with our hypothesis, strength training in young adults induced lowering of the excess VO2 and VO2 slow component. On the contrary, in the elderly strength training may be responsible for a recovered ability to recruit type II muscle fibers that may increase their contribution towards force production in the heavy-intensity domain of an incremental cycling exercise.That ability may increase also their contribution towards force production in the heavy-intensity domain during a constant work rate cycling exercise. This findings are relevant in terms of performance during everyday life, sporting activities and exercise prescription.