Muscle strength, volume and activation following 12-month resistance training in 70-year-old males

Exercise training effect on skeletal muscle motor drive in older adults: A systematic review with meta-analysis of randomized controlled trials

The meta-analysis aimed to determine whether exercise training can positively change indices of motor drive, i.e., the input from the central nervous system to the muscle, and how training characteristics, motor drive assessment, assessed muscle, and testing specificity could modulate the changes in motor drive in older adults. A random-effect meta-analysis model using standardized mean differences (Hedges' g) determined treatment effects. Moderators (e.g., training type and intensity) and meta-regressors (e.g., number of sessions) were performed using mixed- and fixed-effect models. A significant Q-test, followed by pairwise post hoc comparisons, determined differences between levels of the categorical moderators. Methodological quality was assessed using the Cochrane risk of bias tool. Ten randomized controlled trials, 290 older adults, met the inclusion criteria. Only strength and power exercise training were retrieved from the search and included in the analysis. Strength (g = 0.60, 95 % CI 0.24 to 0.96) and power training (g = 0.51, 95 % CI 0.02 to 1.00) increased motor drive compared with a control condition. High (g = 0.66; 95 % CI 0.34 to 0.97) and low-high (g = 1.23; 95 % CI 0.19 to 2.27) combinations of training intensities increased motor drive compared to the control condition. The multi-joint training and testing exercise structure (g = 1.23; 95 % CI 0.79 to 1.67) was more effective in increasing motor drive (Qdf=2 = 14.15; p = 0.001) than the multi-single joint structure (g = 0.46; 95 % CI 0.06 to 0.85). Therefore, strength and power training with high volume and intensity associated with multi-joint training and testing combination of exercises seem to improve skeletal muscle motor drive in older adults effectively.

Validation of a scanning technique with minimal compression for measuring muscle volume with freehand 3D ultrasound

Freehand 3D ultrasound (3D-US) is a promising technique for measuring muscle volume but it requires gel pads or water tanks to limit probe compression on the skin which makes it hard to use in clinical applications. Our objectives were to measure the effect of different compressions on muscle volume in order to assess the clinical applicability of a minimal compression method for lower limb muscles. 4 muscles of the lower limb on 15 healthy volunteers were scanned with a new commercial freehand 3D-US setup accessible to clinical experimentators. Each muscle was scanned with 3 levels of compression: standard compression, minimal compression and gel pad (method validated against MRI). Volume was calculated using software segmentation tools. Acquisitions and segmentations were done by the same examiner. There was a significant impact of standard compression on volume measurements, but no difference between minimal compression and gel pad. Standard compression underestimated volume with a mean bias of 16 mL. For minimal compression, 75 % of measured differences were below the predefined clinically acceptable limits of 10 mL. Mean bias for this method was 1.1 mL. In conclusion, standard compression in freehand 3D-US induces a systematic bias in volume calculations. But, with a trained examiner and the necessary precautions to minimize compression, this bias could be abolished and become acceptable in clinical applications. When a high accuracy is required, gel pads could still be important to consider.

Reliability and Validity of an Ultrasound-Based Protocol for Measurement of Quadriceps Muscle Thickness in Children

Introduction and aims: Accurate determination of skeletal muscle size is of great importance in multiple settings including resistance exercise, aging, disease, and disuse. Ultrasound (US) measurement of muscle thickness (MT) is a method of relatively high availability and low cost. The present study aims to evaluate a multisite ultrasonographic protocol for measurement of MT with respect to reproducibility and correlation to gold-standard measurements of muscle volume (MV) with magnetic resonance imaging (MRI) in children.

Material and methods: 15 children completed the study (11 ± 1 year, 41 ± 8 kg, 137 ± 35 cm). Following 20 min supine rest, two investigators performed US MT measurements of all four heads of the m. quadriceps femoris, at pre-determined sites. Subsequently, MRI scanning was performed and MV was estimated by manual contouring of individual muscle heads.

Results: Ultrasound measurement of MT had an intra-rater reliability of ICC = 0.985–0.998 (CI 95% = 0.972–0.998) and inter-rater reliability of ICC = 0.868–0.964 (CI 95% = 0.637–0.983). The US examinations took less than 15 min, per investigator. Muscle thickness of all individual quadriceps muscles correlated significantly with their corresponding MV as measured by MRI (overall r = 0.789, p < 0.001).

Conclusion: The results of this study indicate that US measurement of MT using a multisite protocol is a competitive alternative to MRI scanning, especially with respect to availability and time consumption. Therefore, US MT could allow for wider clinical and scientific implementation.

Effects of resistance training intensity on muscle quantity/quality in middle-aged and older people: a randomized controlled trial

BACKGROUND

A sarcopenia diagnosis is confirmed by the presence of low muscle quantity or quality under the 2018 revised definition by the European Working Group on Sarcopenia in Older People 2. Imaging methods [i.e. magnetic resonance imaging (MRI)], dual-energy X-ray absorptiometry (DXA), and bioelectrical impedance analysis are tools to evaluate muscle quantity or quality. The present study aimed to investigate whether and how low-intensity and moderate-intensity resistance training improved both muscle quantity and quality measured by MRI, DXA, and segmental bioelectrical impedance spectroscopy (S-BIS) in middle-aged and older people.

METHODS

A single-blind, randomized, controlled trial was conducted. Community-dwelling people aged 50-79 years were randomly allocated to no exercise (no-Ex), low-intensity exercise (low-Ex), and moderate-intensity exercise (moderate-Ex) groups. Participants in the exercise groups performed resistance training for 24 weeks, with loads of 40% and 60% of one repetition maximum in the low-Ex and moderate-Ex groups, respectively. Cross-sectional area (CSA), lean mass, and muscle electrical properties on S-BIS were used to determine the effects of training interventions on muscle quantity and quality of the lower limbs.

RESULTS

Fifty participants (no-Ex 17, age 63.5 ± 8.5 years, women 47.1%; low-Ex 16, age 63.6 ± 8.1 years, women 50.0%; moderate-Ex 17, age 63.5 ± 8.3 years, women 52.9%) completed the 24 week exercise intervention. For the primary outcome, significant intervention effects were found in thigh muscle CSA on MRI between the moderate-Ex and no-Ex groups (+6.8 cm² , P < 0.01). Low-Ex for 24 weeks only increased quadriceps CSA (+2.3 cm² , P < 0.05). The per cent change of thigh muscle CSA (+7.0%, P < 0.01) after 24 week moderate-Ex was higher than that of leg lean mass on DXA (+2.3%, P = 0.088). Moderate-Ex for 24 weeks also improved S-BIS electrical properties related to muscle quantity and quality, including the intracellular resistance index (+0.1 cm² /Ω, P < 0.05), membrane capacitance (+0.7 nF, P < 0.05), and phase angle (+0.3 deg, P < 0.05); their changes were positively correlated with that of thigh muscle CSA (P < 0.01).

CONCLUSIONS

Resistance exercise with moderate intensity improved muscle quantity and quality measured by MRI and S-BIS, whereas that with low intensity only increased muscle quantity in middle-aged and older people. The comparisons among the responses to exercise between the assessment methods indicate the greater value of MRI and S-BIS to measure changes of muscle quantity and quality than of lean mass measured by DXA for assessing the local effects of resistance training.

Human skeletal muscle size with ultrasound imaging: a comprehensive review

Skeletal muscle size is an important factor in assessing adaptation to exercise training and detraining, athletic performance, age-associated atrophy and mobility decline, clinical conditions associated with cachexia, and overall skeletal muscle health. Magnetic resonance (MR) imaging and computed tomography (CT) are widely accepted as the gold standard methods for skeletal muscle size quantification. However, it is not always feasible to use these methods (e.g., field studies, bedside studies, large cohort studies). Ultrasound has been available for skeletal muscle examination for more than 50 years and the development, utility, and validity of ultrasound imaging are underappreciated. It is now possible to use ultrasound in situations where MR and CT imaging are not suitable. This review provides a comprehensive summary of ultrasound imaging and human skeletal muscle size assessment. Since the first study in 1968, more than 600 articles have used ultrasound to examine the cross-sectional area and/or volume of 107 different skeletal muscles in more than 27,500 subjects of various ages, health status, and fitness conditions. Data from these studies, supported by decades of technological developments, collectively show that ultrasonography is a valid tool for skeletal muscle size quantification. Considering the wide-ranging connections between human health and function and skeletal muscle mass, the utility of ultrasound imaging will allow it to be employed in research investigations and clinical practice in ways not previously appreciated or considered.

Safety and Effectiveness of Long-Term Exercise Interventions in Older Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Physical exercise is beneficial to reduce the risk of several conditions associated with advanced age, but to our knowledge, no previous study has examined the association of long-term exercise interventions (≥ 1 year) with the occurrence of dropouts due to health issues and mortality, or the effectiveness of physical exercise versus usual primary care interventions on health-related outcomes in older adults (≥ 65 years old).

OBJECTIVE

To analyze the safety and effectiveness of long-term exercise interventions in older adults.

METHODS

We conducted a systematic review with meta-analysis examining the association of long-term exercise interventions (≥ 1 year) with dropouts from the corresponding study due to health issues and mortality (primary endpoint), and the effects of these interventions on health-related outcomes (falls and fall-associated injuries, fractures, physical function, quality of life, and cognition) (secondary endpoints).

RESULTS

Ninety-three RCTs and six secondary studies met the inclusion criteria and were included in the analyses (n = 28,523 participants, mean age 74.2 years). No differences were found between the exercise and control groups for the risk of dropouts due to health issues (RR = 1.05, 95% CI 0.95-1.17) or mortality (RR = 0.93, 95% CI 0.83-1.04), although a lower mortality risk was observed in the former group when separately analyzing clinical populations (RR = 0.67, 95% CI 0.48-0.95). Exercise significantly reduced the number of falls and fall-associated injuries, and improved physical function and cognition. These results seemed independent of participants' baseline characteristics (age, physical function, and cognitive status) and exercise frequency.

CONCLUSIONS

Long-term exercise training does not overall influence the risk of dropouts due to health issues or mortality in older adults, and results in a reduced mortality risk in clinical populations. Moreover, exercise reduces the number of falls and fall-associated injuries, and improves physical function and cognition in this population.

The influence of resistance training on neuromuscular function in middle-aged and older adults: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Deterioration of neuromuscular function is a major mechanism of age-related strength loss. Resistance training (RT) improves muscle strength and mass. However, the effects of RT on neuromuscular adaptations in middle-aged and older adults are unclear.

METHODS

Randomised controlled RT interventions (≥2 weeks) involving adults aged ≥50 years were identified. Primary outcome measures were voluntary activation (VA), electromyographic (EMG) activity during maximal voluntary contraction (MVC), and antagonist coactivation. Data were pooled using a weighted random-effect model. Sub-analyses were conducted by muscle or muscle group and health status of participants. Sensitivity analysis was based on study quality. P < 0.05 indicated statistical significance.

RESULTS

Twenty-seven studies were included. An effect was found for VA (standardised mean difference [SMD] 0.54, 0.01 to 1.07, P = 0.04), This result remained significant following sensitivity analysis involving only studies that were low risk of bias. Subgroup analyses showed an effect for plantar flexor VA (SMD 1.13, 0.20 to 2.06, P = 0.02) and VA in healthy participants (SMD 1.04, 0.32 to 1.76, P = 0.004). There was no effect for EMG activity or antagonist coactivation of any muscle group (P > 0.05).

DISCUSSION

Resistance training did not alter EMG activity or antagonist coactivation in older adults. Sensitivity analysis resulted in the effect for VA remaining significant, indicating that this finding was not dependent on study quality. Studies predominantly involved healthy older adults (78%), limiting the generalisability of these findings to clinical cohorts. Future research should determine the effects of RT on neuromuscular function in people with sarcopenia and age-related syndromes.

Skeletal Muscle Adaptations Following 80 Weeks of Resistance Exercise in Older Adults

BACKGROUND AND PURPOSE

We followed and documented skeletal muscle adaptations from 4 resistance exercise (RE) prescriptions in older adults over the course of a 2-year, 80-week training study.

METHODS

Forty-three older men and women-65.2 (3.5) years, 167.2 (7.5) cm, and 72.5 (14.7) kg-completed one of the following RE prescriptions: high-load 2 days per week (HL2D; n = 12), low-load 2 days per week (LL2D; n = 9), high-load 3 days per week (HL3D, n = 12), or low-load 3 days per week (LL3D, n = 10). High-load prescriptions consisted of 3 sets of 8 repetitions with 80% 1-repetition maximum (1-RM) and low-load prescriptions completed 3 sets of 16 repetitions with 40% 1-RM. Each session consisted of 12 exercises targeting major muscle groups and training loads were adjusted every fifth week to maintain progressive overload. Participants completed 40 weeks of supervised training, had a 2-month break, and then resumed another 40 weeks of supervised training. Bone-free lean body mass (BFLBM) and appendicular lean mass (ALM) were assessed via dual-energy x-ray absorptiometry and muscle cross-sectional area (mCSA) of the rectus femoris with diagnostic ultrasound across the intervention.

RESULTS AND DISCUSSION

Groups responded similarly with significant increases in total strength (54.9%), upper body strength (42.7%), lower body strength (61.5%), and specific strength (50.3%, strength/BFLBM) over 80 weeks (all P < .001). Significant increases for BFLBM (3.0%), ALM (3.5%), and mCSA (48.7%) were also observed (all P ≤ .019). The only difference among groups indicated HL3D displaying significantly greater percent increase than LL2D for ALM (P = .043).

CONCLUSIONS

Resistance exercise performed 2 or 3 days per week with moderate to heavy loads can improve muscle strength and induce small but perhaps clinically significant increases in BFLBM and mCSA in older adults over a 2-year period of supervised training.

Muscles adaptation to aging and training: architectural changes - a randomised trial

Background

To investigate how anatomical cross-sectional area and volume of quadriceps and triceps surae muscles were affected by ageing, and by resistance training in older and younger men, in vivo.

Methods

The old participants were randomly assigned to moderate (O55, n = 13) or high-load (O80, n = 14) resistance training intervention (12 weeks; 3 times/week) corresponding to 55% or 80% of one repetition maximum, respectively. Young men (Y55, n = 11) were assigned to the moderate-intensity strengthening exercise program. Each group received the exact same training volume on triceps surae and quadriceps group (Reps x Sets x Intensity). The fitting polynomial regression equations for each of anatomical cross-sectional area-muscle length curves were used to calculate muscle volume (contractile content) before and after 12 weeks using magnetic resonance imaging scans.

Results

Only Rectus femoris and medial gastrocnemius muscle showed a higher relative anatomical cross-sectional area in the young than the elderly on the proximal end. The old group displayed a higher absolute volume of non-contractile material than young men in triceps surae (+ 96%). After training, Y55, O55 and O80 showed an increase in total quadriceps (+ 4.3%; + 6.7%; 4.2% respectively) and triceps surae (+ 2.8%; + 7.5%; 4.3% respectively) volume. O55 demonstrated a greater increase on average gains compared to Y55, while no difference between O55 and O80 was observed.

Conclusions

Muscle loss with aging is region-specific for some muscles and uniform for others. Equivalent strength training volume at moderate or high intensities increased muscle volume with no differences in muscle volume gains for old men. These data suggest that physical exercise at moderate intensity (55 to 60% of one repetition maximum) can reverse the aging related loss of muscle mass.

Trial registration

NCT03079180 in ClinicalTrials.gov. Registration date: March 14, 2017.

The influence of sex, training intensity, and frequency on muscular adaptations to 40 weeks of resistance exercise in older adults

The purpose of this investigation was to identify the influence that sex, training intensity, and frequency have on long-term resistance exercise (RE) outcomes in older adults.

METHODS

One-hundred eleven older adults (men: 41, women: 70) completed either: high-intensity RE 2d/week (HI-2D; n = 29), low-intensity RE 2d/week (LI-2D; n = 32), high-intensity RE 3d/week (HI-3D, n = 20), or low-intensity RE 3d/week (LI-3D, n = 30). HI protocols completed 3 sets of 8 repetitions with 80% one-repetition maximum (1-RM) while LI completed 3 sets of 16 repetitions with 40% 1-RM. Total and regional bone free lean body mass (BFLBM) were assessed via dual-energy x-ray absorptiometry and cross-sectional area (mCSA) of the rectus femoris.

RESULTS

mCSA was the only muscle quantity parameter to increase (p = 0.043). Significant trial effects for upper body, lower body, and specific strength were observed (all p < 0.001). Significant sex × time interactions (p < 0.001) were observed for upper and lower body strength, however, men and women displayed similar increases in lower body (45.7 ± 29.6 vs 46.4 ± 34.9%), upper body (33.1 ± 21.0 vs 33.4 ± 24.7%), and specific strength (36.5 ± 28.5 vs 40.1 ± 28.7%). A group × time interaction for lower body strength indicated that at 20-weeks HI-2D and LI-3D displayed greater lower body strength than LI-2D (both p < 0.009), and at 40-weeks HI-2D, HI-3D, and LI-3D displayed significantly greater lower body strength than LI-2D (all p < 0.038).

CONCLUSIONS

These observations indicate that older men and women display similar long-term RE outcomes. Additionally, regardless of frequency or intensity, the current prescriptions were effective for increasing strength, however these data suggest HI-2D > LI-2D and LI-3D > LI-2D but similar outcomes among HI-2D, HI-3D, and LI-3D. The variety of effective RE approaches provides flexibility among older adults for selecting a lifestyle intervention that would be most sustainable.

Promotion of Healthy Aging Within a Community Center Through Behavior Change: Health and Fitness Findings From the AgeWell Pilot Randomized Controlled Trial

The purpose of this randomized controlled trial was to determine if behavior change through individual goal setting (GS) could promote healthy aging, including health and fitness benefits in older adults who attended a community "AgeWell" Center for 12 months. Seventy-five older adults were randomly allocated to either a control or a GS group. Health outcomes were measured at baseline and after 12 months of the participants' having access to the exception of Agewell Center facilities. The findings demonstrate that participation in the Center in itself was beneficial, with improved body composition and reduced cardiovascular risk in both groups (p < .05), and that this kind of community-based resource offers valuable potential for promoting protective behaviors and reducing health risk. However, a specific focus on identifying individual behavior change goals was required in order to achieve increased activity engagement (p < .05) and to bring about more substantial improvements in a range of health, diet, and physical function measures (p < .05).

Resistance Training for Older Adults: Position Statement From the National Strength and Conditioning Association

Fragala, MS, Cadore, EL, Dorgo, S, Izquierdo, M, Kraemer, WJ, Peterson, MD, and Ryan, ED. Resistance training for older adults: position statement from the national strength and conditioning association. J Strength Cond Res 33(8): 2019-2052, 2019-Aging, even in the absence of chronic disease, is associated with a variety of biological changes that can contribute to decreases in skeletal muscle mass, strength, and function. Such losses decrease physiologic resilience and increase vulnerability to catastrophic events. As such, strategies for both prevention and treatment are necessary for the health and well-being of older adults. The purpose of this Position Statement is to provide an overview of the current and relevant literature and provide evidence-based recommendations for resistance training for older adults. As presented in this Position Statement, current research has demonstrated that countering muscle disuse through resistance training is a powerful intervention to combat the loss of muscle strength and muscle mass, physiological vulnerability, and their debilitating consequences on physical functioning, mobility, independence, chronic disease management, psychological well-being, quality of life, and healthy life expectancy. This Position Statement provides evidence to support recommendations for successful resistance training in older adults related to 4 parts: (a) program design variables, (b) physiological adaptations, (c) functional benefits, and (d) considerations for frailty, sarcopenia, and other chronic conditions. The goal of this Position Statement is to a) help foster a more unified and holistic approach to resistance training for older adults, b) promote the health and functional benefits of resistance training for older adults, and c) prevent or minimize fears and other barriers to implementation of resistance training programs for older adults.

The Effects of Resistance Exercise Training on Strength and Functional Tasks in Adults With Limb-Girdle, Becker, and Facioscapulohumeral Dystrophies

Background: The inclusion of resistance training in the treatment and management of muscular dystrophy has previously been discouraged, based on mainly anecdotal evidence. There remains a lack of experimental investigation into resistance training in individuals with muscular dystrophy. The aim of the current study was therefore, to determine the effect of a 12-week resistance training programme on muscle strength and functional tasks in ambulatory adults with muscular dystrophy.

Methods: Seventeen ambulatory adults with muscular dystrophy (Facioscapulohumeral muscular dystrophy: n = 6, Limb-Girdle muscular dystrophy: n = 6, Becker muscular dystrophy: n = 5) were recruited for this study. Participants attended three testing sessions: one session at baseline, one session after a 12-week control period and one session after a 12-week resistance training period. Each testing session consisted of measurements of isometric knee extensor and knee flexor maximum voluntary contraction (MVC) torque (Cybex dynamometer). Participants also completed a timed sit-to-stand, a four steps-stair ascent, and a four steps-stair decent. The 12-week resistance training period consisted of two supervised sessions a week. Each training session included a 5-min warm-up, a step-up exercise, free-standing or assisted squats, knee flexion and knee extension exercises, and an additional 6 single-joint exercises specific to each individual's needs.

Results: Knee flexor MVC torque increased by 13% after the 12-week resistance training programme (p < 0.05), with no change over the control period. Knee extensor MVC torque did not significantly change after the training programme or the control period. Time taken to complete sit-to-stand, stair ascent and stair descent all decreased (improved) following the 12-week training programme (p < 0.05).

Conclusions: A twice-a-week, 12-week, resistance training programme resulted in increased knee flexion strength and improvements in functional tasks in ambulatory adults with muscular dystrophy. This provides support for the inclusion of resistance training in the treatment programmes for these forms of muscular dystrophy.

Simplified Triceps Surae Muscle Volume Assessment in Older Adults

Triceps surae (TS) muscle volume can be estimated in young adults by only considering the maximal anatomical cross-sectional area (ACSA_max) and the length of the muscle due to the presence of a constant muscle-specific shape factor. This study aimed to investigate if this simplified muscle volume assessment is also applicable in older adults or if muscle-specific shape changes with aging. MRI sequences were taken from the dominant leg of 21 older female adults. The boundaries of all three TS muscles (SOL, soleus; GM, gastrocnemius medialis; GL, gastrocnemius lateralis) were manually outlined in transverse image sequences, and muscle volume for each muscle was calculated as the integral of the obtained cross-sectional areas of the contours along the whole length of the muscle (measured volume) and, in addition, by using the average muscle-specific shape factors of each muscle obtained from the ratio of the measured volume and the product of ACSA_max and the muscle length (estimated volume). There were no differences in the measured and estimated muscle volumes (SOL: 357.7 ± 61.8 vs. 358.8 ± 65.3 cm³; GM: 179.5 ± 32.8 vs. 179.8 ± 33.3 cm³; GL: 90.2 ± 15.9 vs. 90.4 ± 14.8 cm³). However, when using the reported shape factors of younger adults instead, we found a significant (p < 0.05) overestimation of muscle volume for SOL and GM with average RMS differences of 6.1 and 7.6%, respectively. These results indicate that corrections of muscle-specific shape factors are needed when using the previously proposed simplified muscle volume assessment as aging may not only be accompanied with muscle atrophy but also changes in the shape of skeletal muscle.

Physical Exercise in the Oldest Old

Societies are progressively aging, with the oldest old (i.e., those aged >80-85 years) being the most rapidly expanding population segment. However, advanced aging comes at a price, as it is associated with an increased incidence of the so-called age-related conditions, including a greater risk for loss of functional independence. How to combat sarcopenia, frailty, and overall intrinsic capacity decline in the elderly is a major challenge for modern medicine, and exercise appears to be a potential solution. In this article, we first summarize the physiological mechanisms underlying the age-related deterioration in intrinsic capacity, particularly regarding those phenotypes related to functional decline. The main methods available for the physical assessment of the oldest old are then described, and finally the multisystem benefits that exercise (or "exercise mimetics" in those situations in which volitional exercise is not feasible) can provide to this population segment are reviewed. In summary, lifetime physical exercise can help to attenuate the loss of many of the properties affected by aging, especially when the latter is accompanied by an inactive lifestyle and benefits can also be obtained in frail individuals who start exercising at an advanced age. Multicomponent programs combining mainly aerobic and resistance training should be included in the oldest old, particularly during disuse situations such as hospitalization. However, evidence is still needed to support the effectiveness of passive physical strategies including neuromuscular electrical stimulation or vibration for the prevention of disuse-induced negative adaptations in those oldest old people who are unable to do physical exercise. © 2019 American Physiological Society. Compr Physiol 9:1281-1304, 2019.

Knee muscle co-contractions are greater in old compared to young adults during walking and stair use

BACKGROUND

Muscle co-contraction is an accepted clinical measure to quantify the effects of aging on neuromuscular control and movement efficiency. However, evidence of increased muscle co-contraction in old compared to young adults remains inconclusive.

RESEARCH QUESTION

Are there differences in lower-limb agonist/antagonist muscle co-contractions in young and old adults, and males and females, during walking and stair use?

METHODS

In a retrospective study, we analyzed data from 20 healthy young and 19 healthy old adults during walking, stair ascent, and stair descent at self-selected speeds, including marker trajectories, ground reaction force, and electromyography activity. We calculated muscle co-contraction at the knee (vastus lateralis vs. biceps femoris) and ankle (tibialis anterior vs. medial gastrocnemius) using the ratio of the common area under a muscle pairs' filtered and normalized electromyography curves to the sum of the areas under each muscle in that pair.

RESULTS

Old compared to young adults displayed 18%-22% greater knee muscle co-contractions during the entire cycle of stair use activities. We found greater (17%-29%) knee muscle co-contractions in old compared to young adults during the swing phase of walking and stair use. We found no difference in ankle muscle co-contractions between the two age groups during all three activities. We found no difference in muscle co-contraction between males and females at the knee and ankle joints for all three activities.

SIGNIFICANCE

Based on our findings, we recommend clinical evaluation to quantify the effects of aging through muscle co-contraction to include the knee joint during dynamic activities like walking and stair use, and independent evaluation of the stance and swing phases.

Combined Resistance and Stretching Exercise Training Benefits Stair Descent Biomechanics in Older Adults

Introduction

Stair descent is a physically demanding activity of daily life and common risk for falls. Age-related deteriorations in ankle joint capacities make stair descent particularly challenging for older adults in built environments, where larger rise steps are encountered. Exercise training may allow older adults to safely cope with the high biomechanical demands of stair descent. However, little is known about the demands of increased rise stairs for older adults, nor the impact of exercise.

Aim

We investigated whether the effects of lower-limb resistance training would alter joint kinetics and movement strategies for older adults when descending standard rise, and increased rise stairs.

Methods

Fifteen older adults descended a four-step stair adjusted to standard rise (170 mm), and increased rise (255 mm) on separate visits. Between these two visits, randomly allocated participants underwent 16 weeks of either: resistance exercise training (n = 8) or habitual activity (n = 7). Kinetic data were measured from step-mounted force plates, and kinematic data from motion-capture cameras. Training involved twice-weekly sessions of lower-limb resistance exercises (three sets of ∼8 repetitions at ∼80% three-repetition maximum), and static plantarflexor stretching (three, 45 s holds per leg).

Results

Standard stairs – Peak ankle joint moments increased (p < 0.002) and knee joint moments decreased (p < 0.01) during descent after exercise training. Peak centre of pressure-centre of mass (CoP-CoM) separations increased in posterior (p = 0.005) and medio-lateral directions (p = 0.04) after exercise training. Exercise training did not affect CoM descent velocity or acceleration. Increased rise stairs – Required greater ankle, knee, and hip moments (p < 0.001), peak downward CoM velocity and acceleration (p = 0.0001), and anterior-posterior CoP-CoM separation (p = 0.0001), but lower medial-lateral CoP-CoM separation (p < 0.05), when compared to standard stair descent. Exercise training did not affect joint kinetics or movement strategies.

Discussion

Exercise training increased the maximum joint ROM, strength and force production of the ankle, and enabled a greater ankle joint moment to be produced in single-leg support (lowering phase) during standard stair descent. Descending increased rise stairs raised the task demand; exercise training could not overcome this. Future research should prioritize the ankle joint in stair descent, particularly targeting plantarflexor torque development across stairs of varying riser heights.

Follow-up efficacy of physical exercise interventions on fall incidence and fall risk in healthy older adults: a systematic review and meta-analysis

Background

The risk of falling and associated injuries increases with age. Therefore, the prevention of falls is a key priority in geriatrics and is particularly based on physical exercising, aiming to improve the age-related decline in motor performance, which is crucial in response to postural threats. Although the benefits and specifications of effective exercise programs have been well documented in pre-post design studies, that is during the treatment, the definitive retention and transfer of these fall-related exercise benefits to the daily life fall risk during follow-up periods remains largely unclear. Accordingly, this meta-analysis investigates the efficacy of exercise interventions on the follow-up risk of falling.

Methods

A systematic database search was conducted. A study was considered eligible if it examined the number of falls (fall rate) and fallers (fall risk) of healthy older adults (≥ 65 years) during a follow-up period after participating in a randomized controlled physical exercise intervention. The pooled estimates of the fall rate and fall risk ratios were calculated using a random-effects meta-analysis. Furthermore, the methodological quality and the risk of bias were assessed.

Results

Twenty-six studies with 31 different intervention groups were included (4739 participants). The number of falls was significantly (p <0.001) reduced by 32% (rate ratio 0.68, 95% confidence interval 0.58 to 0.80) and the number of fallers by 22% (risk ratio 0.78, 95% confidence interval 0.68 to 0.89) following exercising when compared with controls. Interventions that applied posture-challenging exercises showed the highest effects. The methodological quality score was acceptable (73 ± 11%) and risk of bias low.

Conclusions

The present review and meta-analysis provide evidence that physical exercise interventions have the potential to significantly reduce fall rate and risk in healthy older adults. Posture-challenging exercises might be particularly considered when designing fall prevention interventions.

Electronic supplementary material

The online version of this article (10.1186/s40798-018-0170-z) contains supplementary material, which is available to authorized users.

Physical strategies to prevent disuse-induced functional decline in the elderly

Disuse situations can have serious adverse health consequences in the elderly, including mainly functional impairment with subsequent increase in the risk of falls or morbimortality. The present review provides clinicians and care givers with detailed and practical information on the feasibility and effectiveness of physical strategies that are currently available to prevent or attenuate the functional decline that occurs secondarily to disuse situations in the elderly, notably in the hospital setting. In this context, active approaches such as resistance exercises and maximal voluntary contractions, which can be performed both isometrically and dynamically, are feasible during most immobilization situations including in hospitalized old people and represent powerful tools for the prevention of muscle atrophy. Aerobic exercise should also be prescribed whenever possible to reduce the loss of cardiovascular capacity associated with disuse periods. Other feasible strategies for patients who are unwilling or unable to perform volitional exercise comprise neuromuscular electrical stimulation, vibration, and blood flow restriction. However, they should ideally be applied synchronously with voluntary exercise to obtain synergistic benefits.

Reference values of hand-grip dynamometry and the relationship between low strength and mortality in older Chileans

Aim

This study was aimed to set reference values of hand-grip strength by age and sex and validate cut points for risk of functional limitation and mortality in older Chileans.

Methods

This was a pooled analysis of four studies including 6,426 people ≥60 years of nondependent community-dwelling Chileans. After exclusion criteria, the final sample included 5,250 subjects, from whom 2,193 were followed to study all-cause mortality associated with low hand-grip strength. Face-to-face interviews registering sociodemographic characteristics, self-reported chronic diseases, and functional limitations were conducted. Anthropometric measurements and observed mobility were performed by trained professionals. Hand-grip strength was measured with a hand dynamometer T-18 (Country Technology, Inc.) before 2008 or with JAMAR brand from 2008 onwards. Percentiles were calculated through descriptive analysis and quantile regression models for specific groups of age and sex. Adjusted Cox regression hazard models for mortality risk according to low dynamometry condition and covariates were developed.

Results

We deliver reference values of hand-grip strength for older Chileans proposing the 25th percentile as the cut-off point for low dynamometry risk: men ≤27 kg, women ≤15 kg. Low hand-grip strength was associated with Instrumental Activities of Daily Living limitations (p=0.001), and altered physical performance evaluated through the Timed Up and Go test (p=0.0001), grasping (p=0.001), bending (p<0.0001), and lifting (p<0.0001). After Cox proportional hazard regression models were assessed with a median follow-up of 9.2 years, the adjusted risk of all-cause mortality associated with a hand-grip strength lower than the 25th percentile in older Chileans showed a hazard ratio of 1.39 (95% confidence interval: 1.13–1.71).

Conclusion

The cut-off points of dynamometry validated for the older Chileans allow the incorporation in the geriatric evaluation in primary health care of an easy-to-use, inexpensive indicator to identify older adults at risk of sarcopenia, frailty, and dismobility. In addition this also helps to optimize the evaluation of intervention strategies focused on the maintenance of functionality.

Slow movement resistance training using body weight improves muscle mass in the elderly: A randomized controlled trial

To examine the effect of a 12-week slow movement resistance training using body weight as a load (SRT-BW) on muscle mass, strength, and fat distribution in healthy elderly people. Fifty-three men and 35 women aged 70 years old or older without experience in resistance training participated, and they were randomly assigned to a SRT-BW group or control group. The control group did not receive any intervention, but participants in this group underwent a repeat measurement 12 weeks later. The SRT-BW program consisted of 3 different exercises (squat, tabletop push-up, and sit-up), which were designed to stimulate anterior major muscles. Initially, these exercises were performed by 2 sets of 10 repetitions, and subsequently, the number of repetitions was increased progressively by 2 repetitions every 4 weeks. Participants were instructed to perform each eccentric and concentric phase of movement slowly (spending 4 seconds on each movement), covering the full range of motion. We evaluated muscle mass, strength, and fat distribution at baseline and after 12 weeks of training. Changes over 12 weeks were significantly greater in the SRT-BW group than in the control group, with a decrease in waist circumference, hip circumference, and abdominal preperitoneal and subcutaneous fat thickness, and an increase in thigh muscle thickness, knee extension strength, and hip flexion strength. In conclusion, relatively short-term SRT-BW was effective in improving muscle mass, strength, and fat distribution in healthy elderly people.

The Achilles tendon is mechanosensitive in older adults: adaptations following 14 weeks versus 1.5 years of cyclic strain exercise

The aging musculoskeletal system experiences a general decline in structure and function, characterized by a reduced adaptability to environmental stress. We investigated whether the older human Achilles tendon (AT) demonstrates mechanosensitivity (via biomechanical and morphological adaptations) in response to long-term mechanical loading. Thirty-four female adults (60-75 years) were allocated to either a medium-term (14 weeks; N=21) high AT strain cyclic loading exercise intervention or a control group (N=13), with 12 participants continuing with the intervention for 1.5 years. AT biomechanical properties were assessed using ultrasonography and dynamometry. Tendon cross-sectional area (CSA) was investigated by means of magnetic resonance imaging. A 22% exercise-related increment in ankle plantarflexion joint moment, along with increased AT stiffness (598.2±141.2 versus 488.4±136.9 N mm^-1 at baseline), Young's modulus (1.63±0.46 versus 1.37±0.39 GPa at baseline) and about 6% hypertrophy along the entire free AT were identified after 14 weeks of strength training, with no further improvement after 1.5 years of intervention. The aging AT appears to be capable of increasing its stiffness in response to 14 weeks of mechanical loading exercise by changing both its material and dimensional properties. Continuing exercise seems to maintain, but not cause further adaptive changes in tendons, suggesting that the adaptive time-response relationship of aging tendons subjected to mechanical loading is nonlinear.

Age-related changes in the effects of strength training on lower leg muscles in healthy individuals measured using MRI

Background

We previously measured the rate of regaining muscle strength during rehabilitation of lower leg muscles in patients following lower leg casting. Our primary aim in this study was to measure the rate of gain of strength in healthy individuals undergoing a similar training regime. Our secondary aim was to test the ability of MRI to provide a biomarker for muscle function.

Methods

Men and women were recruited in three age groups: 20–30, 50–65 and over 70 years. Their response to resistance training of the right lower leg twice a week for 8 weeks was monitored using a dynamometer and MRI of tibialis anterior, soleus and gastrocnemius muscles at 2 weekly intervals to measure muscle size (anatomical cross-sectional area (ACSA)) and quality (T₂ relaxation). Forty-four volunteers completed the study.

Results

Baseline strength declined with age. Training had no effect in middle-aged females or in elderly men in dorsiflexion. Other groups significantly increased both plantarflexion and dorsiflexion strength at rates up to 5.5 N m week^-1 in young females in plantarflexion and 1.25 N m week^-1 in young males in dorsiflexion. No changes were observed in ACSA or T₂ in any age group in any muscle.

Conclusion

Exercise training improves muscle strength in males at all ages except the elderly in dorsiflexion. Responses in females were less clear with variation across age and muscle groups. These results were not reflected in simple MRI measures that do not, therefore, provide a good biomarker for muscle atrophy or the efficacy of rehabilitation.

The impact of strength training on skeletal muscle morphology and architecture in children and adolescents with spastic cerebral palsy: A systematic review

AIM

The aim of this study was to systematically review the current literature to determine the impact of strength training on skeletal muscle morphology and architecture in individuals aged 4-20 years with spastic type cerebral palsy.

METHODS

A comprehensive search for randomised and non-randomised controlled trials, cohort studies and cross-comparison trials was performed on five electronic databases. Included studies were graded according to level of evidence and assessed for methodological quality using the Downs and Black scale. Quantitative data was analysed using effect sizes.

RESULTS

Six of 304 articles met the inclusion criteria. Methodological quality of the included papers ranged from 14 to 19 (out of 32). A large effect was found on muscle cross-sectional area following strength training, with small to moderate effects on muscle volume and thickness.

CONCLUSION AND IMPLICATIONS

There is preliminary evidence that strength training leads to hypertrophy in children and adolescents with CP. A paucity of studies exist measuring morphological and architectural parameters following strength training in these individuals. Overall low study methodological quality along with heterogeneous study design, dissimilar outcome measures, and lack of adequate control groups, indicated that care is needed when interpreting the results of these studies in isolation.

The Effects of Dietary Omega-3s on Muscle Composition and Quality in Older Adults

This review will focus on findings from the few studies performed to date in humans to examine changes in muscle protein turnover, lean or muscle mass and physical function following fish oil-derived omega-3 fatty acid treatment. Although considerable gaps in our current knowledge exist, hypertrophic responses (e.g., improvements in the rate of muscle protein synthesis and mTOR signaling during increased amino acid availability and an increase in muscle volume) have been reported in older adults following prolonged (8 to 24 weeks) of omega-3 fatty acid supplementation. There is also accumulating evidence that increased omega-3 fatty acid levels in red blood cells are positively related to strength and measures of physical function. As a result, increased omega-3 fatty acid consumption may prove to be a promising low-cost dietary approach to attenuate or prevent aging associated declines in muscle mass and function.

Dose-Response Relationships of Resistance Training in Healthy Old Adults: A Systematic Review and Meta-Analysis

BACKGROUND

Resistance training (RT) is an intervention frequently used to improve muscle strength and morphology in old age. However, evidence-based, dose-response relationships regarding specific RT variables (e.g., training period, frequency, intensity, volume) are unclear in healthy old adults.

OBJECTIVES

The aims of this systematic review and meta-analysis were to determine the general effects of RT on measures of muscle strength and morphology and to provide dose-response relationships of RT variables through an analysis of randomized controlled trials (RCTs) that could improve muscle strength and morphology in healthy old adults.

DATA SOURCES

A computerized, systematic literature search was performed in the electronic databases PubMed, Web of Science, and The Cochrane Library from January 1984 up to June 2015 to identify all RCTs related to RT in healthy old adults.

STUDY ELIGIBILITY CRITERIA

The initial search identified 506 studies, with a final yield of 25 studies. Only RCTs that examined the effects of RT in adults with a mean age of 65 and older were included. The 25 studies quantified at least one measure of muscle strength or morphology and sufficiently described training variables (e.g., training period, frequency, volume, intensity).

STUDY APPRAISAL AND SYNTHESIS METHODS

We quantified the overall effects of RT on measures of muscle strength and morphology by computing weighted between-subject standardized mean differences (SMDbs) between intervention and control groups. We analyzed the data for the main outcomes of one-repetition maximum (1RM), maximum voluntary contraction under isometric conditions (MVC), and muscle morphology (i.e., cross-sectional area or volume or thickness of muscles) and assessed the methodological study quality by Physiotherapy Evidence Database (PEDro) scale. Heterogeneity between studies was assessed using I2 and χ2 statistics. A random effects meta-regression was calculated to explain the influence of key training variables on the effectiveness of RT in terms of muscle strength and morphology. For meta-regression, training variables were divided into the following subcategories: volume, intensity, and rest. In addition to meta-regression, dose-response relationships were calculated independently for single training variables (e.g., training frequency).

RESULTS

RT improved muscle strength substantially (mean SMDbs = 1.57; 25 studies), but had small effects on measures of muscle morphology (mean SMDbs = 0.42; nine studies). Specifically, RT produced large effects in both 1RM of upper (mean SMDbs = 1.61; 11 studies) and lower (mean SMDbs = 1.76; 19 studies) extremities and a medium effect in MVC of lower (mean SMDbs = 0.76; four studies) extremities. Results of the meta-regression revealed that the variables "training period" (p = 0.04) and "intensity" (p < 0.01) as well as "total time under tension" (p < 0.01) had significant effects on muscle strength, with the largest effect sizes for the longest training periods (mean SMDbs = 2.34; 50-53 weeks), intensities of 70-79% of the 1RM (mean SMDbs = 1.89), and total time under tension of 6.0 s (mean SMDbs = 3.61). A tendency towards significance was found for rest in between sets (p = 0.06), with 60 s showing the largest effect on muscle strength (mean SMDbs = 4.68; two studies). We also determined the independent effects of the remaining training variables on muscle strength. The following independently computed training variables are most effective in improving measures of muscle strength: a training frequency of two sessions per week (mean SMDbs = 2.13), a training volume of two to three sets per exercise (mean SMDbs = 2.99), seven to nine repetitions per set (mean SMDbs = 1.98), and a rest of 4.0 s between repetitions (SMDbs = 3.72). With regard to measures of muscle morphology, the small number of identified studies allowed us to calculate meta-regression for the subcategory training volume only. No single training volume variable significantly predicted RT effects on measures of muscle morphology. Additional training variables were independently computed to detect the largest effect for the single training variable. A training period of 50-53 weeks, a training frequency of three sessions per week, a training volume of two to three sets per exercise, seven to nine repetitions per set, a training intensity from 51 to 69% of the 1RM, a total time under tension of 6.0 s, a rest of 120 s between sets, and a rest of 2.5 s between repetitions turned out to be most effective.

LIMITATIONS

The current results must be interpreted with caution because of the poor overall methodological study quality (mean PEDro score 4.6 points) and the considerable large heterogeneity (I2) = 80%, χ2 = 163.1, df = 32, p < 0.01) for muscle strength. In terms of muscle morphology, our search identified nine studies only, which is why we consider our findings preliminary. While we were able to determine a dose-response relationship based on specific individual training variables with respect to muscle strength and morphology, it was not possible to ascertain any potential interactions between these variables. We recognize the limitation that the results may not represent one general dose-response relationship.

CONCLUSIONS

This systematic literature review and meta-analysis confirmed the effectiveness of RT on specific measures of upper and lower extremity muscle strength and muscle morphology in healthy old adults. In addition, we were able to extract dose-response relationships for key training variables (i.e., volume, intensity, rest), informing clinicians and practitioners to design effective RTs for muscle strength and morphology. Training period, intensity, time under tension, and rest in between sets play an important role in improving muscle strength and morphology and should be implemented in exercise training programs targeting healthy old adults. Still, further research is needed to reveal optimal dose-response relationships following RT in healthy as well as mobility limited and/or frail old adults.

The acute effect of neuromuscular activation in resistance exercise on human skeletal muscle with the interpolated twitch technique

[Purpose] The purpose of this study was to perform a quantitative assessment of neuromechanical adaptation in skeletal muscles and to propose the scientific underpinnings of the acute effects induced by resistance exercise. [Subjects] The subjects in this study were 11 healthy adult men in their 20s who had no orthopedic history at the time of the study. To examine any signs of resistance exercise-induced changes in the ankle plantar flexor, the subjects were directed to perform a standing barbell calf raise routine. [Methods] Subjects were to carry a load equal to their weights and to perform five sets of ten repetitions. The maximal voluntary isometric contraction torque, resting twitch torque, muscle inhibition, root mean square of muscular activation, contraction time, and half relaxation time were analyzed by synchronizing a dynamometer, an electrical stimulator, and an electromyography system. [Results] The maximal voluntary isometric contraction torque appeared to decline, but the change was not statistically significant. The decline of resting twitch torque, on the other hand, was found to be statistically significant. Muscle inhibition and root mean square of muscular activation were both reduced, but both changes were not statistically significant. Lastly, contraction time and half relaxation time both statistically decreased significantly after resistance exercise. [Conclusion] These results indicate that the acute effects of resistance exercise have a greater impact on the peripheral mechanical system itself, rather than on neurological factors, in terms of the generation of muscle force.

Effects of resistance training with moderate vs heavy loads on muscle mass and strength in the elderly: A meta-analysis

The purpose of the present study was to perform a meta-analysis to compare the efficacy of heavy (∼80% of one repetition maximum, 1RM) vs light-moderate load (∼45% 1RM) resistance training (RT) programs in inducing strength gains and skeletal muscle hypertrophy in elderly people. To assess the role of training volumes, studies in which training protocols were matched for mechanical work were independently analyzed. In all 15 studies included (448 subjects, age 67.8 years), when comparing heavy with light-moderate loads, strength gains tended to be larger following RT with higher intensities of load, with the resulting total population effect being μ = 0.430 (P = 0.060). Effect sizes were substantially smaller in "work-matched" studies (μ = 0.297, P = 0.003). Training with higher loads also provoked marginally larger gains in muscle size, although the degree of training-induced muscle hypertrophy was generally small (0.056 < μ < 0.136). To conclude, provided a sufficient number of repetitions is performed, RT at lower than traditionally recommended intensities of load may suffice to induce substantial gains in muscle strength in elderly cohorts.

Longevity and skeletal muscle mass: the role of IGF signalling, the sirtuins, dietary restriction and protein intake

Advancing age is associated with a progressive loss of skeletal muscle (SkM) mass and function. Given the worldwide aging demographics, this is a major contributor to morbidity, escalating socio-economic costs and ultimately mortality. Previously, it has been established that a decrease in regenerative capacity in addition to SkM loss with age coincides with suppression of insulin/insulin-like growth factor signalling pathways. However, genetic or pharmacological modulations of these highly conserved pathways have been observed to significantly enhance life and healthspan in various species, including mammals. This therefore provides a controversial paradigm in which reduced regenerative capacity of skeletal muscle tissue with age potentially promotes longevity of the organism. This paradox will be assessed and considered in the light of the following: (i) the genetic knockout, overexpression and pharmacological models that induce lifespan extension (e.g. IRS-1/s6K KO, mTOR inhibition) versus the important role of these signalling pathways in SkM growth and adaptation; (ii) the role of the sirtuins (SIRTs) in longevity versus their emerging role in SkM regeneration and survival under catabolic stress; (iii) the role of dietary restriction and its impact on longevity versus skeletal muscle mass regulation; (iv) the crosstalk between cellular energy metabolism (AMPK/TSC2/SIRT1) and survival (FOXO) versus growth and repair of SkM (e.g. AMPK vs. mTOR); and (v) the impact of protein feeding in combination with dietary restriction will be discussed as a potential intervention to maintain SkM mass while increasing longevity and enabling healthy aging.

FAST CP: protocol of a randomised controlled trial of the efficacy of a 12-week combined Functional Anaerobic and Strength Training programme on muscle properties and mechanical gait deficiencies in adolescents and young adults with spastic-type cerebral palsy

INTRODUCTION

Individuals with cerebral palsy (CP) have muscles that are smaller, weaker and more resistant to stretch compared to typically developing people. Progressive resistance training leads to increases in muscle size and strength. In CP, the benefits of resistance training alone may not transfer to improve other activities such as walking; however, the transfer of strength improvements to improved mobility may be enhanced by performing training that involves specific functional tasks or motor skills. This study aims to determine the efficacy of combined functional anaerobic and strength training in (1) influencing muscle strength, structure and function and (2) to determine if any changes in muscle strength and structure following training impact on walking ability and gross motor functional capacity and performance in the short (following 3 months of training) and medium terms (a further 3 months post-training).

METHODS AND ANALYSIS

40 adolescents and young adults with CP will be recruited to undertake a 12-week training programme. The training programme will consist of 3 × 75 min sessions per week, made up of 5 lower limb resistance exercises and 2-3 functional anaerobic exercises per session. The calf muscles will be specifically targeted, as they are the most commonly impacted muscles in CP and are a key muscle group involved in walking. If, as we believe, muscle properties change following combined strength and functional training, there may be long-term benefits of this type of training in slowing the deterioration of muscle function in people with spastic-type CP.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the ethics committees at The University of Queensland (2014000066) and Children's Health Queensland (HREC/15/QRCH/30). The findings will be disseminated by publications in peer-reviewed journals, conferences and local research organisations' media.

TRIAL REGISTRATION NUMBER

Australian and New Zealand Clinical Trials Registry (ACTRN12614001217695).

NMR imaging estimates of muscle volume and intramuscular fat infiltration in the thigh: variations with muscle, gender, and age

Muscle mass is particularly relevant to follow during aging, owing to its link with physical performance and autonomy. The objectives of this work were to assess muscle volume (MV) and intramuscular fat (IMF) for all the muscles of the thigh in a large population of young and elderly healthy individuals using magnetic resonance imaging (MRI) to test the effect of gender and age on MV and IMF and to determine the best representative slice for the estimation of MV and IMF. The study enrolled 105 healthy young (range 20-30 years) and older (range 70-80 years) subjects. MRI scans were acquired along the femur length using a three-dimension three-point Dixon proton density-weighted gradient echo sequence. MV and IMF were estimated from all the slices. The effects of age and gender on MV and IMF were assessed. Predictive equations for MV and IMF were established using a single slice at various femur levels for each muscle in order to reduce the analysis process. MV was decreased with aging in both genders, particularly in the quadriceps femoris. IMF was largely increased with aging in men and, to a lesser extent, in women. Percentages of MV decrease and IMF increase with aging varied according to the muscle. Predictive equations to predict MV and IMF from single slices are provided and were validated. This study is the first one to provide muscle volume and intramuscular fat infiltration in all the muscles of the thigh in a large population of young and elderly healthy subjects.

Is co-contraction responsible for the decline in maximal knee joint torque in older males?

While it is often reported that muscular coactivation increases with age, the mechanical impact of antagonist muscles, i.e., the antagonist torque, remains to be assessed. The aim of this study was to determine if the mechanical impact of the antagonist muscles may contribute to the age-related decline in the resultant torque during maximal voluntary contraction in knee flexion (KF) and knee extension (KE). Eight young (19-28 years old) and eight older (62-81 years old) healthy males participated in neuromuscular testing. Maximal resultant torque was simultaneously recorded with the electromyographic activity of quadriceps and hamstring muscles. The torque recorded in the antagonist muscles was estimated using a biofeedback technique. Resultant torques significantly decreased with age in both KF (-41 %, p < 0.005) and KE (-35 %, p < 0.01). Agonist and antagonist torques were significantly reduced in KF (-44 %, p < 0.05; -57 %, p < 0.05) and in KE (-37 %, p < 0.01; -50 %, p < 0.05). The torque elicited by double twitch stimulation (-37 %, p < 0.01) and the activation level (-12 %, p < 0.05) of quadriceps was significantly lower in older men compared to young men. This study showed that antagonist torques were not responsible for age-related declines in KF and KE resultant torques. Therefore, decreased resultant torques with age, in particular in KE, can primarily be explained by impairments of the peripheral factors (excitation-contraction coupling) as well as by decreased neural agonist activation.

Human neuromuscular structure and function in old age: A brief review

Natural adult aging is associated with many functional impairments of the human neuromuscular system. One of the more observable alterations is the loss of contractile muscle mass, termed sarcopenia. The loss of muscle mass occurs primarily due to a progressive loss of viable motor units, and accompanying atrophy of remaining muscle fibers. Not only does the loss of muscle mass contribute to impaired function in old age, but alterations in fiber type and myosin heavy chain isoform expression also contribute to weaker, slower, and less powerful contracting muscles. This review will focus on motor unit loss associated with natural adult aging, age-related fatigability, and the age-related differences in strength across contractile muscle actions.

Muscle Quality in Older Adults

The population of older adults in the United States is steadily growing and identifying factors that contribute to healthy aging is a public health priority. Changes in body composition are a hallmark of the aging process and have been implicated in the loss of physical function among older adults. In particular, age-related declines in muscle strength and power occur at a faster rate than the loss of muscle mass (sarcopenia), and this suggests a decrease in muscle quality of older adults. Muscle quality has traditionally been defined as muscle function (strength or power) per unit of muscle size (mass or cross-sectional area) and a growing body of literature suggests that lower body muscle quality may be critical for maintaining functional independence with age. However, the literature regarding the definition of muscle quality and its relationship with health outcomes in older adults has not been adequately reviewed. Thus, the aim of this report is to highlight the contemporary literature regarding age-related changes in muscle quality and its relationship with health outcomes in community-dwelling older adults.

Impaired hypertrophy in myoblasts is improved with testosterone administration

We investigated the ability of testosterone (T) to restore differentiation in multiple population doubled (PD) murine myoblasts, previously shown to have a reduced differentiation in monolayer and bioengineered skeletal muscle cultures vs. their parental controls (CON) (Sharples et al., 2011, 2012 [7,26]). Cells were exposed to low serum conditions in the presence or absence of T (100nM)±PI3K inhibitor (LY294002) for 72h and 7 days (early and late muscle differentiation respectively). Morphological analyses were performed to determine myotube number, diameter (μm) and myonuclear accretion as indices of differentiation and myotube hypertrophy. Changes in gene expression for myogenin, mTOR and myostatin were also performed. Myotube diameter in CON and PD cells increased from 17.32±2.56μm to 21.02±1.89μm and 14.58±2.66μm to 18.29±3.08μm (P≤0.05) respectively after 72h of T exposure. The increase was comparable in both PD (+25%) and CON cells (+21%) suggesting a similar intrinsic ability to respond to exogenous T administration. T treatment also significantly increased myonuclear accretion (% of myotubes expressing 5+ nuclei) in both cell types after 7 days exposure (P≤0.05). Addition of PI3K inhibitor (LY294002) in the presence of T attenuated these effects in myotube morphology (in both cell types) suggesting a role for the PI3K pathway in T stimulated hypertrophy. Finally, PD myoblasts showed reduced responsiveness to T stimulated mRNA expression of mTOR vs. CON cells and T also reduced myostatin expression in PD myoblasts only. The present study demonstrates testosterone administration improves hypertrophy in myoblasts that basally display impaired differentiation and hypertrophic capacity vs. their parental controls, the action of testosterone in this model was mediated by PI3K/Akt pathway.

Responsiveness of muscle size and strength to physical training in very elderly people: a systematic review

The purpose of this review was to determine whether very elderly muscle (>75 years) hypertrophies in response to physical training. The databases MEDLINE; EMBASE; CINAHL Plus and SPORTDiscus were systematically literature searched with reference lists of all included studies and relevant reviews. Controlled trials (inactive elderly control group) involving healthy elderly participants over 75 years participating in an intervention complying with an established definition of physical training were included. Data extraction and quality assessment were performed using the PEDro scale. Data analysis was performed on muscle size and strength using RevMan (software version 5.1). Four studies were included of which four of four measured changes in gross muscle size. Training induced increases in muscle size from 1.5%-15.6% were reported in three of four studies, and one of four studies reported a decrease in muscle size (3%). The greatest gain in muscle mass was observed in a study of whole body vibration training. Meta-analysis of three studies found an increase of thigh muscle cross-sectional area (mean difference 2.31 cm(2) or 0.2%, 95% confidence interval (CI): 0.62 to 4.00; P = 0.008) and muscle strength (standardized mean difference 1.04, 95% CI: 0.65 to 1.43; P < 0.001). Physical training when delivered as resistance training has the ability to elicit hypertrophy and increase muscle strength in very elderly muscle.

Variability and distribution of muscle strength and its determinants in humans

INTRODUCTION

Inter-individual variability in measurements of muscle strength and its determinants was identified to: (1) produce a normative data set describing the normal range and (2) determine whether some measurements are more informative than others when evaluating inter-individual differences.

METHODS

Functional and morphological characteristics of the vastus lateralis were measured in 73 healthy, untrained adult men.

RESULTS

Inter-individual variability (coefficient of variation) was greater for isometric maximal voluntary contraction (MVC) torque (18.9%) compared with fascicle force (14.6%; P=0.025) and physiological cross-sectional area (PCSA; 17.2%) compared with anatomical cross-sectional area (ACSA, 13.0%; P<0.0005). The relationship between ACSA and isometric MVC torque (r(2)  =0.56) was weaker than that between PCSA and fascicle force (r(2)  =0.68).

CONCLUSIONS

These results provide a normative data set on inter-individual variability in a variety of muscle strength-related measurements and illustrate the benefit of using more stringent measures of muscle properties. Muscle Nerve 49: 879-886, 2014.

Comparison of power and EMG during 6-s all-out cycling between young and older women

To investigate the effects of ageing on the neural control strategies governing sprint cycling on a friction-loaded cycle-ergometer, 10 older (aged 70-83 yr) and 8 young (aged 19-35 yr) healthy women completed seven 6-s all-out cycling trials against varying loads. Root mean square (RMS), median frequency and muscle fibre conduction velocity were determined from the vastus lateralis of the dominant limb during each pedal stroke. Peak power was 43% lower in the older group compared to the younger (p < 0.001) and was accompanied by a significantly lower RMS (p < 0.05). No differences were observed in the other electromyography (EMG) parameters between the groups (p > 0.05). ΔRMS from the first to the sixth second during each trial was found to increase significantly with the development of power output in both groups (p < 0.05). For the first time during an all-out 6-s cycle trial, it has been demonstrated that older women's lower mechanical power output was accompanied by a significantly lower RMS, which indicates a decline in either the number of active of motor units or a reduced discharge rate. Hence, changes in motor units can be regarded as a contributory factor to the decline of muscle power with advancing age. Overall, though, similar neural strategies are adopted in both younger and older populations.

Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength; a quantitative review

Changing demographics make it ever more important to understand the modifiable risk factors for disability and loss of independence with advancing age. For more than two decades there has been increasing interest in the role of sarcopenia, the age-related loss of muscle or lean mass, in curtailing active and healthy aging. There is now evidence to suggest that lack of strength, or dynapenia, is a more constant factor in compromised wellbeing in old age and it is apparent that the decline in muscle mass and the decline in strength can take quite different trajectories. This demands recognition of the concept of muscle quality; that is the force generating per capacity per unit cross-sectional area (CSA). An understanding of the impact of aging on skeletal muscle will require attention to both the changes in muscle size and the changes in muscle quality. The aim of this review is to present current knowledge of the decline in human muscle mass and strength with advancing age and the associated risk to health and survival and to review the underlying changes in muscle characteristics and the etiology of sarcopenia. Cross-sectional studies comparing young (18–45 years) and old (>65 years) samples show dramatic variation based on the technique used and population studied. The median of values of rate of loss reported across studies is 0.47% per year in men and 0.37% per year in women. Longitudinal studies show that in people aged 75 years, muscle mass is lost at a rate of 0.64–0.70% per year in women and 0.80–00.98% per year in men. Strength is lost more rapidly. Longitudinal studies show that at age 75 years, strength is lost at a rate of 3–4% per year in men and 2.5–3% per year in women. Studies that assessed changes in mass and strength in the same sample report a loss of strength 2–5 times faster than loss of mass. Loss of strength is a more consistent risk for disability and death than is loss of muscle mass.

Using submaximal contractions to predict the maximum force-generating ability of muscles

INTRODUCTION

Muscle weakness can be caused by decreases in either the maximum force-generating ability of a muscle (MFGA) or neural drive from the nervous system (e.g., after a stroke). Presently, there is no agreed-upon practical method for calculating the MFGA in individuals with central nervous system pathology. The purpose of this study was to identify the best method for determining MFGA.

METHODS

The predicted and estimated MFGA of the muscles of 23 non-neurologically impaired subjects (13 males, 21.9 ± 1.9 years) were compared using the burst superimposition, twitch interpolation, doublet interpolation, twitch-to-tetanus ratio, and the adjusted burst superimposition methods.

RESULTS

The adjusted burst superimposition test was the most accurate predictor of MFGA.

CONCLUSIONS

Further testing is needed to validate the use of the adjusted burst superimposition test in a neurologically impaired population.

Reduction of myoblast differentiation following multiple population doublings in mouse C2 C12 cells: a model to investigate ageing?

Ageing skeletal muscle displays declines in size, strength, and functional capacity. Given the acknowledged role that the systemic environment plays in reduced regeneration (Conboy et al. [2005] Nature 433: 760-764), the role of resident satellite cells (termed myoblasts upon activation) is relatively dismissed, where, multiple cellular divisions in-vivo throughout the lifespan could also impact on muscular deterioration. Using a model of multiple population doublings (MPD) in-vitro thus provided a system in which to investigate the direct impact of extensive cell duplications on muscle cell behavior. C(2) C(12) mouse skeletal myoblasts (CON) were used fresh or following 58 population doublings (MPD). As a result of multiple divisions, reduced morphological and biochemical (creatine kinase, CK) differentiation were observed. Furthermore, MPD cells had significantly increased cells in the S and decreased cells in the G1 phases of the cell cycle versus CON, following serum withdrawal. These results suggest continued cycling rather than G1 exit and thus reduced differentiation (myotube atrophy) occurs in MPD muscle cells. These changes were underpinned by significant reductions in transcript expression of: IGF-I and myogenic regulatory factors (myoD and myogenin) together with elevated IGFBP5. Signaling studies showed that decreased differentiation in MPD was associated with decreased phosphorylation of Akt, and with later increased phosphorylation of JNK1/2. Chemical inhibition of JNK1/2 (SP600125) in MPD cells increased IGF-I expression (non-significantly), however, did not enhance differentiation. This study provides a potential model and molecular mechanisms for deterioration in differentiation capacity in skeletal muscle cells as a consequence of multiple population doublings that would potentially contribute to the ageing process.

Effects of Strength and Power Training on Neuromuscular Variables in Older Adults

The purpose of this study was to compare the neuromuscular adaptations produced by strength-training (ST) and power-training (PT) regimens in older individuals. Participants were balanced by quadriceps cross-sectional area (CSA) and leg-press 1-repetition maximum and randomly assigned to an ST group (n= 14; 63.6 ± 4.0 yr, 79.7 ± 17.2 kg, and 163.9 ± 9.8 cm), a PT group (n= 16; 64.9 ± 3.9 yr, 63.9 ± 11.9 kg, and 157.4 ± 7.7 cm), or a control group (n= 13; 63.0 ± 4.0 yr, 67.2 ± 10.8 kg, and 159.8 ± 6.8 cm). ST and PT were equally effective in increasing (a) maximum dynamic and isometric strength (p< .05), (b) increasing quadriceps muscle CSA (p< .05), and (c) decreasing electrical mechanical delay of the vastus lateralis muscle (p< .05). There were no significant changes in neuromuscular activation after training. The novel finding of the current study is that PT seems to be an attractive alternative to regular ST to maintain and improve muscle mass.

Sirtuin 1 regulates skeletal myoblast survival and enhances differentiation in the presence of resveratrol

Sirtuin 1 also known as NAD-dependent deacetylase sirtuin 1, is a protein that in humans is encoded by the Sirt1 gene. Sirt1 is an enzyme that deacetylates proteins that contribute to cellular regulation and is a key regulator of cell defenses and survival in response to stress. Deletion of Sirt1 abolishes the increase in lifespan induced by calorie restriction or sublethal cytokine stress, indicating that Sirt1 promotes longevity and survival. We have demonstrated that administration of a sublethal dose of tumour necrosis factor-α (TNF-α; 1.25 ng ml(-1)) inhibits myotube formation, and co-incubation with insulin-like growth factor I (IGF-I; 1.5 ng ml(-1)) facilitates C2 myoblast death rather than rescuing differentiation. A higher dose of TNF-α (10 ng ml(-1)) resulted in significant apoptosis, which was rescued by IGF-I (1.5 ng ml(-1); 50% rescue; P < 0.05). We aimed to investigate the role of Sirt1 in the conflicting roles of IGF-I. Quantitative real-time PCR revealed that Sirt1 expression was elevated in myoblasts following incubation of 10 ng ml(-1) TNF-α or 1.25 ng ml(-1) TNF-α plus IGF-I (fivefold and 7.2-fold increases versus control, respectively; P < 0.05). A dose of 10 ng ml(-1) TNF-α induced ∼21 ± 0.7% apoptosis, which was reduced (∼50%; P < 0.05) when administered with IGF-I. Likewise, Sirt1 expression was elevated following 10 ng ml(-1) TNF-α administration, but was reduced (∼30%; P < 0.05) in the presence of IGF-I. C2C12 myoblasts, a subclone of the C2 cell line produced for their differentiation potential and used to examine intrinsic ageing, unlike C2 cells, do not die in the presence of TNF-α and do not upregulate Sirt1. As conditions that induced the greatest myoblast stress/damage resulted in elevated Sirt1 expression, we investigated the effects of Sirt1 gene silencing. Treatment with 10 ng ml(-1) TNF-α or co-incubation with 1.25 ng ml(-1) TNF-α and 1.5 ng ml(-1) IGF-I resulted in apoptosis (20.33 ± 2.08 and 19 ± 2.65%, respectively), which was increased when myoblasts were pretreated with Sirt1 small interfering RNA (31 ± 2.65 and 27.33 ± 2.52%, respectively; P < 0.05) and was reduced (14.33 ± 3.05%, P < 0.05 and 12.78 ± 4.52%, P = 0.054) by resveratrol, which also significantly rescued the block on differentiation. In conclusion, Sirt1 expression increases in conditons of stress, potentially serving to reduce or dampen myoblast death.

Skeletal muscle properties in rheumatoid arthritis patients

PURPOSE

Disability in patients with rheumatoid arthritis (RA) is a multifactorial process involving various unaccounted factors. Loss of lean body mass plays an important role in impaired physical function, and exercise studies in RA have shown promising results in restoring muscle mass, strength, and function. However, no comprehensive assessment of the muscle characteristics has been undertaken to determine whether qualitative changes in muscle also contribute to RA disability. This study explores the physiological muscle properties of a community-based population with stable RA.

METHODS

Vastus lateralis (VL) force and physiological cross-sectional area (PCSA), voluntary muscle activation capacity, and contractile properties were assessed in 23 patients with stable RA (age = 60 ± 2 yr (mean ± SEM); 16 women) and age- and sex-matched healthy controls (age = 60 ± 3 yr). Measurements with EMG were obtained during maximal isometric knee extension contractions, with resting and superimposed electrical stimulations. Concentric knee extension contractions were also assessed. Pennation angle and VL volume were measured with ultrasound to determine fiber fascicle length and PCSA. Muscle-specific force was calculated (VL force/VL PCSA). Body composition using dual-energy x-ray absorptiometry and objective physical function were also measured.

RESULTS

The patients displayed typical features of RA with reduced physical function (P = 0.001-0.09), a trend toward lower appendicular lean mass (P = 0.09) and increased total body fat (P < 0.05) relative to controls. However, there were no differences in specific force, contractile properties, voluntary activation capacity, and contraction velocity (P = 0.41-0.99). VL PCSA was reduced (P < 0.05) with minor architectural changes in patients with RA.

CONCLUSIONS

Physiological properties of muscle that determine specific force are not compromised in patients with stable RA despite deficits in physical function.