Changes in muscle thickness of gastrocnemius and soleus associated with age and sex

Age-related changes in ultrasound-assessed muscle composition and postural stability

While the simultaneous degradation of muscle composition and postural stability in aging are independently highly investigated due to their association with fall risk, the interplay between the two has received little attention. Thus, the purpose of this study is to explore how age-related changes in muscle composition relate to postural stability. To that aim, we collected posturography measures and ultrasound images of the dominant Vastus Lateralis and Biceps Brachii from 32 young (18-35 year old) and 34 older (65-85 year old) participants. Muscle properties were quantified with echo-intensity and texture-based metrics derived from gray-level co-occurrence matrix analysis, and postural stability with the variability of the center of pressure during bipedal stance tasks. Ultrasound parameters revealed that young muscle possessed lower echo-intensity and higher homogeneity compared to the elderly. Echo-intensity and muscle thickness, and several texture-based parameters possessed outstanding young versus older classification performance. A canonical correlation analysis demonstrated a significant relationship between ultrasound and postural measures only within the young group (r = 0.53, p < 0.002), where those with 'better' muscle composition displayed larger postural sways. Our results indicate that, in older individuals, postural stability and muscle composition, two common fall risk factors, are unrelated. In view of this decoupling, both may contribute independently to fall risk. Furthermore, our data support the view that texture-based parameters provide a robust alternative to echo-intensity in providing markers of muscle composition.

Maximal sustainable energy intake during transatlantic ocean rowing is insufficient for total energy expenditure and skeletal muscle mass maintenance

Studies of extreme endurance have suggested that there is an alimentary limit to energy intake (EI) of ∼2.5 × resting metabolic rate (RMR). To gain further insight, this study aimed to simultaneously measure EI, total energy expenditure (TEE) body mass and muscle mass in a large cohort of males and females of varying ages during a transatlantic rowing race. Forty-nine competitors (m = 32, f = 17; age 24-67 years; time at sea 46 ± 7 days) in the 2020 and 2021 Talisker Whisky Atlantic Challenge rowed 12-18 hday-1 for ∼3000 miles. TEE was assessed in the final week of the row using 2 H2 18 O doubly labelled water, and EI was analysed from daily ration packs over this period. Thickness of relatively active (vastus lateralis, intermedius, biceps brachaii and rectus abdominus) and inactive (gastrocnemius, soleus and triceps) muscles was measured pre (<7 days) and post (<24 h) row using ultrasound. Body mass was measured and used to calculate RMR from standard equations. There were no sex differences in males and females in EI (2.5 ± 0.5 and 2.3 ± 0.4 × RMR, respectively, P = 0.3050), TEE (2.5 ± 1.0 and 2.3 ± 0.4 × RMR, respectively, P = 0.5170), or body mass loss (10.2 ± 3.1% and 10.0 ± 3.0%, respectively, P = 0.8520), and no effect of age on EI (P = 0.5450) or TEE (P = 0.9344). Muscle loss occurred exclusively in the calf (15.7% ± 11.4% P < 0.0001), whilst other muscles remained unchanged. After 46 days of prolonged ultra-endurance ocean rowing incurring 10% body mass loss, maximal sustainable EI of ∼2.5 × RMR was unable to meet total TEE suggesting that there is indeed a physiological capacity to EI.

The contribution of mitochondria to age-related skeletal muscle wasting: A sex-specific perspective

As people age, their skeletal muscle (SkM) experiences a decline in mitochondrial functionality and density, which leads to decreased energy production and increased generation of reactive oxygen species. This cascade of events, in turn, might determine the loss of SkM mass, strength and quality. Even though the mitochondrial processes dysregulated by aging, such as oxidative phosphorylation, mitophagy, antioxidant defenses and mtDNA transcription, are the same in both sexes, mitochondria age differently in the SkM of men and women. Indeed, the onset and magnitude of the impairment of these processes seem to be influenced by sex-specific factors. Sexual hormones play a pivotal role in the regulation of SkM mass through both genomic and non-genomic mechanisms. However, the precise mechanisms by which these hormones regulate mitochondrial plasticity in SkM are not fully understood. Although the presence of estrogen receptors in mitochondria is recognized, it remains unclear whether androgen receptors affect mitochondrial function. This comprehensive review critically dissects the current knowledge on the interplay of sex in the aging of SkM, focusing on the role of sex hormones and the corresponding signaling pathways in shaping mitochondrial plasticity. Improved knowledge on the sex dimorphism of mitochondrial aging may lead to sex-tailored interventions that target mitochondrial health, which could be effective in slowing or preventing age-related muscle loss.

How susceptible are our Achilles Tendons? Sonoanatomical assessment. A cross-sectional study

OBJECTIVE

the aim of this study is to observe whether there are ultrasound changes between men and women in the Achilles tendon at rest, at maximum passive force is applied and during walking.

MATERIAL AND METHODS

it was a cross-sectional study involving 27 healthy young participants recruited as volunteers between April to July 2022. A variety of data was recorded: (age, Body Mass Index, sex, smoking, current injury status, allergies, medications, previous surgeries, type of sport, and number of weekly workouts) and ultrasound measurements at rest and at passive force (Cross Sectional Area Achilles Tendon length, tendon thickness, Cross Sectional Area and pennation angle of the soleus muscle to the Achilles Tendon).

RESULTS

women demonstrated a statistically significant lower proximal and median thickness both at rest (4.5 vs 5.1 mm with p < 0.001 for proximal thickness; 4.4 vs 5.3 mm with p < 0.001 for median thickness) as well as during maximum eccentric contraction (4.3 vs 4.8 mm with p=<0.001 for proximal thickness; 4.1 vs 4.8 mm with p < 0.001 for median thickness).

CONCLUSION

there are significant sonoanatomical differences in vivo Achilles tendon between men and women.

Suitable ultrasound screening method for older adults with disability to identify low muscle mass

Objective

This study aimed to investigate the accuracy and consistency of different ultrasound protocols for the measurement of gastrocnemius muscle (GM) thickness and to identify a suitable ultrasound scheme that can be used to detect the low muscle mass in older with disability.

Materials and methods

In this cross-sectional study, each participant underwent three different ultrasound protocols for the measurement of the GM thickness, and each measurement was repeated three times. The three measurement schemes were as follows: method A, lying on the examination bed in a prone position with legs stretched and relaxed and feet hanging outside the examination bed; method B, lateral right side lying position with legs separated (left leg flexed and right leg in a relaxed state); and method C, right side lying position with legs together and lower limb muscles in a relaxed state. The low muscle mass was determined by averaging two or three measurements of the GM thickness determined using different sonographic protocols.

Results

The study included 489 participants. The difference in the prevalence of low muscle mass identified between two and three replicates of the same measurement protocol ranged from 0 to 1.3%. Considering the three repeated measurements of the method A as the reference, the area under the curve (AUC) in different measurement schemes were 0.977-1 and 0.973-1 in males and females, respectively. Furthermore, male and female Kappa values from low to high were 0.773, 0.801, 0.829, 0.839, and 0.967 and 0.786, 0.794, 0.804, 0.819, and 0.984, respectively.

Conclusion

Different ultrasound measurement protocols showed high accuracy and consistency in identifying low muscle mass. Repeating the measurements two or three times was found to be feasible.

Musculoskeletal Ultrasound Shows Muscle Mass Changes during Post-Acute Care Hospitalization in Older Men: A Prospective Cohort Study

This study aimed to prospectively assess changes in muscle thickness (MT) and the cross-sectional area (CSA) of the rectus femoris (RF) muscle in a cohort of older adults, using musculoskeletal ultrasound at admission and at a 2-week follow-up during hospitalization in a post-acute care unit. Differences in frailty status and correlations of MT-RF and CSA-RF with current sarcopenia diagnostic criteria were also studied. Forty adults aged 79.5 (SD 9.5) years (57.5% women) participated, including 14 with frailty and 26 with pre-frailty. In the first week follow-up, men had a significant increase in MT (0.9 mm [95%CI 0.3 to 1.4], p = 0.003) and CSA (0.4 cm2 [95%CI 0.1 to 0.6], p = 0.007). During the second week, men continued to have a significant increase in MT (0.7 mm [95%CI 0.0 to 1.4], p = 0.036) and CSA (0.6 cm2 [95%CI 0.01 to 1.2], p = 0.048). Patients with frailty had lower values of MT-RF and CSA-RF at admission and during the hospitalization period. A moderate-to-good correlation of MT-RF and CSA with handgrip strength, fat-free mass and gait speed was observed. Musculoskeletal ultrasound was able to detect MT-RF and CSA-RF changes in older adults admitted to a post-acute care unit.

Ultrasound exploration of muscle characteristic changes and diabetic peripheral neuropathy in diabetic patients

PURPOSE

Using brightness mode ultrasound combined with shear wave elastography, this study aims to detect structural and functional changes of the medial head of gastrocnemius (MG) in type 2 diabetes mellitus (T2DM) patients with or without diabetic peripheral neuropathy (DPN).

METHODS

149 T2DM patients (DPN group and non-DPN group) and 60 healthy volunteers (control group) were enrolled. We measured the absolute difference of fascicle length (FL), pennation angle (PA), and shear wave velocity (SWV) of both MG in neutral position and maximal ankle joint's plantar flexion and calculated ΔFL, ΔPA, and ΔSWV. These three parameters, along with muscle thickness (MT), were compared among the three groups.

RESULTS

In the DPN group, the MG's MT, ΔPA, and ΔSWV were significantly lower than in the non-DPN group (p < 0.01); these parameters achieved the highest scores in the control group (p < 0.01). The area under the receiver operating characteristic curve of the combination of ΔSWV and ΔFL was the largest for predicting inpatients with or without DPN.

CONCLUSIONS

Decreased muscle mass (MT) and muscle contractibility (ΔFL and ΔSWV) were detected in patients with T2DM, with or without DPN. ΔSWV and ΔFL of the MG showed high-diagnostic accuracy for DPN warning signs.

Growth differentiation factor 11 induces skeletal muscle atrophy via a STAT3-dependent mechanism in pulmonary arterial hypertension

Skeletal muscle wasting is a clinically remarkable phenotypic feature of pulmonary arterial hypertension (PAH) that increases the risk of mortality. Growth differentiation factor 11 (GDF11), centrally involved in PAH pathogenesis, has an inhibitory effect on skeletal muscle growth in other conditions. However, whether GDF11 is involved in the pathogenesis of skeletal muscle wasting in PAH remains unknown. We showed that serum GDF11 levels in patients were increased following PAH. Skeletal muscle wasting in the MCT-treated PAH model is accompanied by an increase in circulating GDF11 levels and local catabolic markers (Fbx32, Trim63, Foxo1, and protease activity). In vitro GDF11 activated phosphorylation of STAT3. Antagonizing STAT3, with Stattic, in vitro and in vivo, could partially reverse proteolytic pathways including STAT3/socs3 and iNOS/NO in GDF11-meditated muscle wasting. Our findings demonstrate that GDF11 contributes to muscle wasting and the inhibition of its downstream molecule STAT3 shows promise as a therapeutic intervention by which muscle atrophy may be directly prevented in PAH.

Muscle fiber type-dependence effect of exercise on genomic networks in aged mice models

Skeletal muscles are made up of various muscle fiber type including slow and fast-twitch fibers. Because each muscle fiber has its own physiological characteristics, the effects of aging and exercise vary depending on the type of muscle fiber. We used bioinformatics screening techniques such as differentially expressed gene analysis, gene ontology analysis and gene set enrichment analysis, to try to understand the genetic differences between muscle fiber types. The experiment and gene expression profiling in this study used the soleus (SOL, slow-twitch muscle) and gastrocnemius (GAS, fast-twitch muscle). According to our findings, fatty acid metabolism is significantly up-regulated in SOL compared to GAS, whereas the glucose metabolism pathway is significantly down-regulated in SOL compared to GAS.

Furthermore, apoptosis and myogenesis patterns differ between SOL and GAS. SOL did not show differences in apoptosis due to the aging effect, but apoptosis in GAS was significantly up-regulated with age. Apoptosis in GAS of old groups is significantly reduced after 4 weeks of aerobic exercise, but no such finding was found in SOL. In terms of myogenesis, exercise intervention up-regulated this process in GAS of old groups but not in SOL. Taken together, muscle fiber type significantly interacts with aging and exercise. Despite the importance of the interaction between these factors, large-scale gene expression data has rarely been studied. We hope to contribute to a better understanding of the relationship between muscle fiber type, aging and exercise at the molecular level.

Pharmacological hypogonadism impairs molecular transducers of exercise-induced muscle growth in humans

BACKGROUND

The relative role of skeletal muscle mechano-transduction in comparison with systemic hormones, such as testosterone (T), in regulating hypertrophic responses to exercise is contentious. We investigated the mechanistic effects of chemical endogenous T depletion adjuvant to 6 weeks of resistance exercise training (RET) on muscle mass, function, myogenic regulatory factors, and muscle anabolic signalling in younger men.

METHODS

Non-hypogonadal men (n = 16; 18-30 years) were randomized in a double-blinded fashion to receive placebo (P, saline n = 8) or the GnRH analogue, Goserelin [Zoladex (Z), 3.6 mg, n = 8], injections, before 6 weeks of supervised whole-body RET. Participants underwent dual-energy X-ray absorptiometry (DXA), ultrasound of m. vastus lateralis (VL), and VL biopsies for assessment of cumulative muscle protein synthesis (MPS), myogenic gene expression, and anabolic signalling pathway responses.

RESULTS

Zoladex suppressed endogenous T to within the hypogonadal range and was well tolerated; suppression was associated with blunted fat free mass [Z: 55.4 ± 2.8 to 55.8 ± 3.1 kg, P = 0.61 vs. P: 55.9 ± 1.7 to 57.4 ± 1.7 kg, P = 0.006, effect size (ES) = 0.31], composite strength (Z: 40 ± 2.3% vs. P: 49.8 ± 3.3%, P = 0.03, ES = 1.4), and muscle thickness (Z: 2.7 ± 0.4 to 2.69 ± 0.36 cm, P > 0.99 vs. P: 2.74 ± 0.32 to 2.91 ± 0.32 cm, P < 0.0001, ES = 0.48) gains. Hypogonadism attenuated molecular transducers of muscle growth related to T metabolism (e.g. androgen receptor: Z: 1.2 fold, P > 0.99 vs. P: 1.9 fold, P < 0.0001, ES = 0.85), anabolism/myogenesis (e.g. IGF-1Ea: Z: 1.9 fold, P = 0.5 vs. P: 3.3 fold, P = 0.0005, ES = 0.72; IGF-1Ec: Z: 2 fold, P > 0.99 vs. P: 4.7 fold, P = 0.0005, ES = 0.68; myogenin: Z: 1.3 fold, P > 0.99 vs. P: 2.7 fold, P = 0.002, ES = 0.72), RNA/DNA (Z: 0.47 ± 0.03 to 0.53 ± 0.03, P = 0.31 vs. P: 0.50 ± 0.01 to 0.64 ± 0.04, P = 0.003, ES = 0.72), and RNA/ASP (Z: 5.8 ± 0.4 to 6.8 ± 0.5, P > 0.99 vs. P: 6.5 ± 0.2 to 8.9 ± 1.1, P = 0.008, ES = 0.63) ratios, as well as acute RET-induced phosphorylation of growth signalling proteins (e.g. AKT^ser473 : Z: 2.74 ± 0.6, P = 0.2 vs. P: 5.5 ± 1.1 fold change, P < 0.001, ES = 0.54 and mTORC1^ser2448 : Z: 1.9 ± 0.8, P > 0.99 vs. P: 3.6 ± 1 fold change, P = 0.002, ES = 0.53). Both MPS (Z: 1.45 ± 0.11 to 1.50 ± 0.06%·day^-1 , P = 0.99 vs. P: 1.5 ± 0.12 to 2.0 ± 0.15%·day^-1 , P = 0.01, ES = 0.97) and (extrapolated) muscle protein breakdown (Z: 93.16 ± 7.8 vs. P: 129.1 ± 13.8 g·day^-1 , P = 0.04, ES = 0.92) were reduced with hypogonadism result in lower net protein turnover (3.9 ± 1.1 vs. 1.2 ± 1.1 g·day^-1 , P = 0.04, ES = 0.95).

CONCLUSIONS

We conclude that endogenous T sufficiency has a central role in the up-regulation of molecular transducers of RET-induced muscle hypertrophy in humans that cannot be overcome by muscle mechano-transduction alone.

Neural and muscular alterations of the plantar flexors in middle-aged women

INTRODUCTION

Considering the large population of middle-aged adults, it is important to understand the age-related change in lower limb muscles and the possible mechanisms before old age (> 65 years old). The purpose of this study was to investigate age-related neural and muscular alterations of the plantar flexors in young and middle-aged women.

METHODS

Twenty two middle-aged (54.0 ± 5.8 yrs) and 17 young (21.8 ± 1.4 yrs) recreationally active women performed rapid maximal voluntary isometric contractions (MVIC) of the plantar flexors. Absolute and normalized rate of torque development (RTD) and electromyography (EMG) were examined. Electrical stimulation was used to examine voluntary activation and contractile properties of the muscle. Ultrasonography was used to examine medial and lateral gastrocnemius muscle thickness and pennation angle. A 6-minute walk and sit to stand task were also performed by all participants.

RESULTS

The middle-aged women had significantly lower MVIC torque (141 ± 49 vs. 109 ± 30 Nm, P = 0.031), absolute RTD (753.0 ± 313.6 vs. 423.0 ± 156.1 Nm/s, P = 0.001), and normalized peak RTD (554.0 ± 191.0 vs. 388.0 ± 91.9% MVIC/s, P = 0.001). Normalized early RTD_0-50 and late RTD_100-200, voluntary activation, and EMG were similar between groups. Resting twitch data showed that time to peak (124.0 ± 20.4 vs. 143.0 ± 16.7 ms, P = 0.002) and half relaxation time (73.1 ± 15.2 vs. 107.0 ± 28.2 ms, P < 0.001) was significantly faster for the young women. Thickness was greater in the lateral gastrocnemius (1.6 ± 0.2 vs. 1.4 ± 0.2 cm, P = 0.006) for the young women. Pennation angle of both muscles were greater for the young women (15.8 ± 3.9 vs. 13.1 ± 2.7 degrees, P < 0.05). Performance of the 6-minute walk was similar between groups, however, the young women performed more repetitions during the sit to stand task (25.6 ± 6.7 vs. 18.3 ± 4.7 reps, P < 0.001).

CONCLUSION

Compared to young women, middle-age women were shown to have lower MVIC torque, peak RTD, and functional performance. Muscle architecture and contractile properties are affected by aging.

Correlation between muscle architecture and anaerobic power in athletes involved in different sports

Athletes cultivate highly developed muscles based on their sport category, creating a body shape that matches the characteristics of that sports category. We tested the significance of the correlation between muscle development characteristics and anaerobic power in athletes to build a database for each category. Fifty-eight college athletes participated in this study. To assess muscle characteristics, muscle thickness (MT) and fascicle angle (FA) were measured by ultrasonography (US) in lower limb. Furthermore, anaerobic power was measured with the Wingate test. Analysis of the correlation between muscle structure and anaerobic power revealed significant differences between the sports categories, except for the MT of the medial head of gastrocnemius (Gm), lateral head of gastrocnemius, and FA of Gm. A significant difference was observed for all parameters, except for the arrival time to peak power in the anaerobic power items; in particular, a high degree of correlation in mean power/kg and peak power/kg was observed. A similar tendency was observed in the correlation between muscle structure and anaerobic power in most sports categories, but certain muscle characteristic factors were prominent in each sport. Based on these, it is possible to contribute to predicting and promoting athletic performance.

Gender Difference in Architectural and Mechanical Properties of Medial Gastrocnemius-Achilles Tendon Unit In Vivo

This study aims to explore whether gender differences exist in the architectural and mechanical properties of the medial gastrocnemius–Achilles tendon unit (gMTU) in vivo. Thirty-six healthy male and female adults without training experience and regular exercise habits were recruited. The architectural and mechanical properties of the gMTU were measured via an ultrasonography system and MyotonPRO, respectively. Independent t-tests were utilized to quantify the gender difference in the architectural and mechanical properties of the gMTU. In terms of architectural properties, the medial gastrocnemius (MG)’s pennation angle and thickness were greater in males than in females, whereas no substantial gender difference was observed in the MG’s fascicle length; the males possessed Achilles tendons (ATs) with a longer length and a greater cross-sectional area than females. In terms of mechanical properties, the MG’s vertical stiffness was lower and the MG’s logarithmic decrement was greater in females than in males. Both genders had no remarkable difference in the AT’s vertical stiffness and logarithmic decrement. Gender differences of individuals without training experience and regular exercise habits exist in the architectural and mechanical properties of the gMTU in vivo. The MG’s force-producing capacities, ankle torque, mechanical efficiency and peak power were higher in males than in females. The load-resisting capacities of AT were greater and the MG strain was lesser in males than in females. These findings suggest that males have better physical fitness, speed and performance in power-based sports events than females from the perspective of morphology and biomechanics.

Plantar flexor strength at different knee positions in older and young males and females

INTRODUCTION

This study examined the effects of age and knee position (fully extended, K0; 90° flexed, K90) on plantar flexor maximal voluntary contraction (MVC) torque and the rate of torque development (RTD) in both sexes.

METHODS

The following parameters were measured in 32 older (66-81 yr, 17 males and 15 females) and 37 young (20-30 yr, 18 males and 19 females) adults: evoked peak twitch torque, time to peak twitch torque, RTD of the twitch torque, MVC torque, RTD at early (0-50 ms, RTD_0-50) and later (100-200 ms, RTD_100-200) time intervals during explosive contractions, voluntary activation (VA%) during MVC, root mean square of the electromyogram (RMS-EMG) during MVC and explosive contractions, thickness of the triceps surae, and pennation angle of the medial gastrocnemius. The magnitudes of the differences were interpreted based on Cohen's d (d).

RESULTS

Age-related difference in RTD_0-50 was greater for females (d = 1.36) than males (d = 1.03) and vice versa for MVC torque and RTD_100-200. For young adults, MVC torque, RTDs, and RMS-EMGs of the gastrocnemius but not the soleus were significantly higher in K0 than in K90. For older adults, no differences in voluntary RTDs were observed between K0 and K90, and RMS-EMGs of the gastrocnemius were higher in K90 than in K0, except for that of the lateral gastrocnemius in the early time intervals during explosive contraction. The age-related difference in the effect of knee position for RTD_0-50 was higher in females than males, and vice versa for MVC torque and RTD_100-200.

CONCLUSION

The results suggested that the effects of age and knee joint angle on the plantar flexor performance were more prominent in the early phase of force production for females and were more apparent in the later phase and maximal force for males.

A proposal for a new classification of soleus muscle morphology

INTRODUCTION

The soleus muscle (SM) is located in the superficial posterior compartment of the leg, together with the gastrocnemius muscle (GM) and plantaris muscle. There is little information on the morphological variability (pennation) of the SM. The aim of the study is to characterize the variations in the morphology of the pennation of the SM and to create the first accurate classification.

MATERIAL AND METHODS

Eighty lower limbs (40 left, and 40 right) fixed in 10% formalin solution were examined. The morphology of the central tendon, medial and lateral aponeuroses was evaluated, together with the pennation angle.

RESULTS

In all cases, the soleus muscle was present. Four types could be distinguished based on muscle fibre morphology. In order of frequency: Type 1 - bipennate (43.75%); Type 4 - non-pennate (36.25%); Type 2 - unipennate (15%); Type 3 - multipennate (5%). No significant difference in type distribution was observed with regard to body side (p=0.9018) or gender (p=0.0844).

CONCLUSION

The soleus muscle is characterized by high morphological variability. Based on the pennation angle, four types (1-4) of soleus muscle are distinguishable.

Evaluation of effects of aging on skeletal muscle elasticity using shear wave elastography

PURPOSE

To evaluate the effects of aging on skeletal muscle stiffness in relaxed and contracted status using shear wave elastography (SWE).

MATERIALS AND METHODS

A total of 57 participants were enrolled to this institutional review board approved prospective study. Medial head of the gastrocnemius muscle (GM) of all participants were examined bilaterally by a single radiologist in prone position. Muscle thickness, stiffness values in both relaxed and contracted status were measured. Stiffness increase rate (SIR) was calculated for all muscles. The Spearman's correlation test was used for correlation analyses. Mann-Whitney U test was used to compare subgroups.

RESULTS

The mean age of the participants was 41.15 ± 16.19 (range, 18-74). The means of stiffness values of medial head of GM were 12.51 ± 2.56 kPa and 81.74 ± 15.77 kPa in relaxed and contracted status, respectively. The mean of SIR values was 5.62 ± 1.05 (range, 3.18-8.66). The stiffness values of relaxed and contracted medial head of GM had moderate to strong inverse correlations with age for both dominant and non-dominant extremities (r range: -0.703 to -0.590). Age subgroup analyses revealed significant differences in muscle thickness and stiffness values, whereas no significant difference was found in SIR values.

CONCLUSION

In conclusion, despite the decrease in stiffness of skeletal muscle with advancing age, SIR remained similar. Any improvement in stiffness values of skeletal muscle in relaxed status may play pivotal role in the management of sarcopenia.

Suggested Assessments for Sarcopenia in Patients With Stroke Who Can Walk Independently

Objective

To investigate variables for assessment of stroke-related sarcopenia that are alternative options to the current assessment for sarcopenia, which focuses on age-related sarcopenia and also has limitations in addressing sarcopenia due to weakness resulting from stroke.

Methods

Forty patients (17 men, 23 women; mean age, 66.9±15.4 years) with first-ever stroke who can walk independently were included. Muscle mass was determined by measuring ultrasonographic muscle thickness of vastus intermedius, rectus femoris, tibialis anterior, medial gastrocnemius, and biceps brachii muscles in addition to using the skeletal muscle index (SMI) with bioelectrical impedance analysis. Muscle strength was assessed with the Medical Research Council (MRC) sum score as well as handgrip (HG) strength. Physical performance was measured by the Berg Balance Scale (BBS) along with 4-meter gait speed (4MGS). Correlations between each assessment in the three categories were analyzed and adjusted by stroke severity, comorbidity, and nutritional status.

Results

For muscle mass, SMI showed the highest correlation with the tibialis anterior muscle (r=0.783, p<0.001) among the other muscles. Regarding muscle strength, the MRC sum score correlated with the HG (r=0.660, p<0.001). For physical performance, the BBS correlated with the 4MGS (r=0.834, p<0.001). The same result was obtained after adjusting for factors of stroke severity, comorbidity, and nutritional status.

Conclusion

These results suggest that ultrasonographic muscle thickness of the tibialis anterior, the MRC sum score, and BBS might be alternatives to SMI, HG, and usual gait speed for sarcopenia in stroke patients.

Mechanical properties and collagen fiber orientation of tendon in young and elderly

BACKGROUND

The purpose of this study was to investigate differences in the mechanical properties and collagen fiber orientation of tendon structures between young and elderly groups.

METHODS

The mechanical properties of tendon structures in medial gastrocnemius muscle were measured using ultrasonography during ramp and ballistic contractions. Tendon collagen fiber orientation was estimated from coefficient of variation (CV) of echogenicity on transverse ultrasonic images of Achilles tendon.

FINDINGS

Differences in elongation between ramp and ballistic contractions of elderly were significantly smaller than those of young group at 20-80% of MVC. During ramp contraction, hysteresis of elderly was significantly higher than that of young, whereas no difference in hysteresis during ballistic contraction was found between the two groups. Difference in hysteresis between ramp and ballistic contractions of elderly tended to be lower than that of young group. Mean echogenicity of elderly was significantly higher than that of young group, whereas no difference in CV of echogenicity was found between the two groups.

INTERPRETATION

These results suggest that smaller differences in elongation and hysteresis between ramp and ballistic contractions of elderly may be related to decreased water content within tendons. Furthermore, no difference in collagen fiber orientation of tendons was noted between the two groups.

Assessment of core and lower limb muscles for static/dynamic balance in the older people: An ultrasonographic study

BACKGROUND

sufficient research has not been conducted to determine the role of core and lower limb muscles in providing balance in older people.

OBJECTIVE

to investigate the relationships between the thickness of core/lower limb muscles and static/dynamic balance in older people.

METHODS

the study included a total of 68 older people (≥ 65 years) and 68 gender-matched young subjects, aged 20-40 years. Balance, knee proprioception sense, regional and total muscle measurements and grip strength were assessed using a force platform system, isokinetic dynamometer, ultrasound imaging, bioelectrical impedance analysis and Jamar dynamometer, respectively.

RESULTS

all the static (postural sway) parameters were higher and all the dynamic (limits of stability) parameters were lower in the older adults compared to the young adults (all P<0.05). The diaphragm was thicker and all the other muscles (except for multifidus and tibialis anterior) were thinner in the older group (all P<0.05). A higher error of knee proprioception sense was determined at 45 and 70 degrees in the older subjects (both P<0.001). According to the multivariate analyses, significant predictors for balance were age, gender, height, and rectus femoris, vastus intermedius and diaphragm muscle thicknesses in the older group, and age, gender, height, grip strength, and rectus abdominis, internal oblique, longissimus, tibialis anterior and soleus muscle thicknesses in the young group (all P<0.05).

CONCLUSIONS

the thickness of core/lower limb muscles are important determinants of balance in both older and young adults. These findings could provide a strong rationale for strengthening specific (abdominal and quadriceps) muscles to prevent falls and regional sarcopenia, and to improve posture/balance in the older population.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03791047.

ETHICS COMMITTEE APPROVAL

Hacettepe University Non-interventional Clinical Research Ethics Board. Decision number:GO 18/506-39.

Ultrasound Characteristics of Foot and Ankle Structures in Healthy, Coper, and Chronically Unstable Ankles

OBJECTIVE

Ankle sprains constitute approximately 85% of all ankle injuries, and up to 70% of people experience residual symptoms. While the injury to ligaments is well understood, the potential role of other foot and ankle structures has not been explored. The objective was to characterize and compare selected ankle structures in participants with and without a history of lateral ankle sprain.

METHODS

A total of 71 participants were divided into 31 healthy, 20 coper, and 20 chronic ankle instability groups. Ultrasound images of the anterior talofibular and calcaneofibular ligaments, fibularis tendons and muscles, tibialis posterior, and Achilles tendon were obtained. Thickness, length, and cross-sectional areas were measured and compared among groups.

RESULTS

When under tension, the anterior talofibular ligament (ATFL) was longer in copers and chronic ankle instability groups compared to healthy participants (P < .001 and P = .001, respectively). The chronic ankle instability group had the thickest ATFL and calcaneofibular ligament among the 3 groups (p < 0.001). No significant differences (P > .05) in tendons and muscles were observed among the 3 groups.

CONCLUSIONS

The ultrasound protocol proved reliable and was used to evaluate the length, thickness, and cross-sectional areas of selected ankle structures. The length of the ATFL and the thickness of the ATFL and calcaneofibular ligament were longer and thicker in injured groups compared to healthy.

Age-related changes in muscle elasticity and thickness of the lower extremities are associated with physical functions among community-dwelling older women

AIM

To clarify the age-related changes in muscle elasticity or thickness of the lower extremities in older women, and to analyze their relationship with physical functions.

METHODS

The muscle elasticity and thickness of the rectus femoris and medial head of the gastrocnemius of 102 young women (young group) and 221 elderly women (elderly group) were measured using ultrasonography. In the elderly group, physical functions, including knee extension strength, Timed Up and Go test, single-leg standing, maximum gait speed and Four Square Step Test were also measured.

RESULTS

The elasticity of the rectus femoris and medial head of the gastrocnemius were significantly higher, but the muscle thickness of both muscles was significantly lower in the elderly group than in the young group (both P < 0.001). In the elderly group, the elasticity of the rectus femoris was significantly correlated with Timed Up and Go test, maximum gait speed and Four Square Step Test (ρ = 0.481, r = -0.387 and ρ = 0.401, respectively, all P < 0.001), and the medial head of the gastrocnemius was similar (ρ = 0.471, r = -0.489 and ρ = 0.422, respectively, all P < 0.001). The muscle thickness of the rectus femoris was significantly associated with knee extension strength (r = 0.444, P < 0.001).

CONCLUSIONS

Older women showed age-related changes in high elasticity and atrophy of the rectus femoris and medial head of the gastrocnemius. The high elasticity of both muscles, not muscle thickness, was associated with dynamic balance and walking ability. Geriatr Gerontol Int 2019; 19: 61-65.

Exercise-induced calf muscle hyperemia: quantitative mapping with low-dose dynamic contrast enhanced magnetic resonance imaging

Peripheral artery disease (PAD) in the lower extremities often leads to intermittent claudication. In the present study, we proposed a low-dose DCE MRI protocol for quantifying calf muscle perfusion stimulated with plantar flexion and multiple new metrics for interpreting perfusion maps, including the ratio of gastrocnemius over soleus perfusion (G/S; for assessing the vascular redistribution between the two muscles) and muscle perfusion normalized by whole body perfusion (for quantifying the muscle's active hyperemia). Twenty-eight human subjects participated in this Institutional Review Board-approved study, with 10 healthy subjects ( group A) for assessing interday reproducibility and 8 healthy subjects ( group B) for exploring the relationship between plantar-flexion load and induced muscle perfusion. In a pilot group of five elderly healthy subjects and five patients with PAD ( group C), we proposed a protocol that measured perfusion for a low-intensity exercise and for an exhaustion exercise in a single MRI session. In group A, perfusion estimates for calf muscles were highly reproducible, with correlation coefficients of 0.90-0.93. In group B, gastrocnemius perfusion increased linearly with the exercise workload ( P < 0.05). With the low-intensity exercise, patients with PAD in group C showed substantially lower gastrocnemius perfusion compared with elderly healthy subjects [43.4 (SD 23.5) vs. 106.7 (SD 73.2) ml·min^-1·100 g^-1]. With exhaustion exercise, G/S [1.0 (SD 0.4)] for patients with PAD was lower than both its low-intensity level [1.9 (SD 1.3)] and the level in elderly healthy subjects [2.7 (SD 2.1)]. In conclusion, the proposed MRI protocol and the new metrics are feasible for quantifying exercise-induced muscle hyperemia, a promising functional test of PAD. NEW & NOTEWORTHY To quantitatively map exercise-induced hyperemia in calf muscles, we proposed a high-resolution MRI method shown to be highly reproducible and sensitive to exercise load. With the use of low contrast, it is feasible to measure calf muscle hyperemia for both low-intensity and exhaustion exercises in a single MRI session. The newly proposed metrics for interpreting perfusion maps are promising for quantifying intermuscle vascular redistribution or a muscle's active hyperemia.

Effects of Age on Strength and Morphology of Toe Flexor Muscles

Study Design Descriptive, cross-sectional. Background Age-related muscle atrophy is common in lower-limb muscles. We therefore speculated that foot muscles may also diminish with age. However, there is a paucity of literature characterizing foot muscle strength and morphology, and any relationship between these 2, in older people. Objective To compare the strength and size of the toe flexor muscles of older adults relative to their younger counterparts. Methods Seventeen young adults with a normal foot type were matched by sex and body mass index to 17 older adults with a normal foot type, from an available sample of 41 younger (18 to 50 years of age) and 44 older (60 or more years of age) adults. Among the matched groups (n = 34), muscle thickness and cross-sectional area for 5 intrinsic and 2 extrinsic toe flexor muscles were obtained using ultrasound. Toe strength was assessed using a pressure platform. Differences in toe flexor strength and muscle size between the young and older matched groups were determined using analysis of covariance (controlling for height). Correlations between strength and size of the toe flexor muscles of the pooled group (n = 34) were also calculated. Results Toe strength and the thickness and cross-sectional area of most foot muscles were significantly reduced in the older adults (P<.05). Hallux and toe flexor strength values were strongly correlated with the size of the intrinsic toe flexor muscles. Conclusion The smaller foot muscles appear to be affected by sarcopenia in older adults. This could contribute to reduced toe flexion force production and may affect the ability of older people to walk safely. Interventions aimed at reversing foot muscle atrophy in older people require further investigation. J Orthop Sports Phys Ther 2016;46(12):1065-1070. Epub 29 Oct 2016. doi:10.2519/jospt.2016.6597.

Time-dependent neuromuscular parameters in the plantar flexors support greater fatigability of old compared with younger males

Older adults are more fatigable than young during dynamic tasks, especially those that involve moderate to fast unconstrained velocity shortening contractions. Rate of torque development (RTD), rate of velocity development (RVD) and rate of neuromuscular activation are time-dependent neuromuscular parameters which have not been explored in relation to age-related differences in fatigability. The purpose was to determine whether these time-dependent measures affect the greater age-related fatigability in peak power during moderately fast and maximal effort shortening plantar flexions. Neuromuscular properties were recorded from 10 old (~ 78 years) and 10 young (~ 24 years) men during 50 maximal-effort unconstrained velocity shortening plantar flexions against a resistance equivalent to 20% maximal voluntary isometric contraction torque. At task termination, peak power, and angular velocity, and torque at peak power were decreased by 30, 18, and 16%, respectively, for the young (p < 0.05), and 46, 28, 30% for the old (p < 0.05) compared to pre-fatigue values with the old exhibiting greater reductions across all measures (p<0.05). Voluntary RVD and RTD decreased, respectively, by 24 and 26% in the young and by 47 and 40% in the old at task termination, with greater decrements in the old (p < 0.05). Rate of neuromuscular activation of the soleus decreased over time for both age groups (~ 47%; p < 0.05), but for the medial gastrocnemius (MG) only the old experienced significant decrements (46%) by task termination. All parameters were correlated strongly with the fatigue-related reduction in peak power (r = 0.81-0.94, p < 0.05), except for MG and soleus rates of neuromuscular activation (r = 0.25-0.30, p > 0.10). Fatigue-related declines in voluntary RTD and RVD were both moderately correlated with MG rate of neuromuscular activation (r = 0.51-0.52, p < 0.05), but exhibited a trend with soleus (r = 0.39-0.41, p = 0.07-0.09). Thus, time-dependent factors, RVD and RTD, are likely important indicators of intrinsic muscle properties leading to the greater age-related decline in peak power when performing a repetitive dynamic fatigue task, which may be due to greater fatigue-related central impairments for the older men than young.

Age-Related Differences in Muscle Shear Moduli in the Lower Extremity

This study investigated the age-related differences in shear moduli of the rectus femoris muscle (RF), the lateral head of the gastrocnemius muscle (LG) and the soleus muscle (SOL) using shear wave ultrasound elastography. Thirty-one young individuals and 49 elderly individuals volunteered for this study. The shear modulus of RF was determined at 50% of the thigh length, and those of LG and SOL were determined at 30% of the lower leg length. RF and LG shear moduli were significantly higher in young individuals than in elderly individuals, but there was no age-related difference in SOL shear modulus. From the standpoint of an index reflecting muscle mechanical properties, it is suggested that the lower muscle shear moduli of RF and LG are the reason for the decreased explosive muscle strength in the lower extremity and the increased risk of falls for elderly individuals.

The effect of knee joint angle on plantar flexor power in young and old men

Human adult aging is associated with a loss of strength, contractile velocity and hence, power. The principal plantar flexors, consisting of the bi-articular gastrocnemeii and the mono-articular soleus, appear to be affected differently by the aging process. However, the age-related effect of knee joint angle on the torque-angular velocity relationship and power production of this functionally important muscle group is unknown. The purpose was to determine whether flexing the knee, thereby reducing the gastrocnemius contribution to plantar flexion, would exacerbate the age-related decrements in plantar flexion power, or shift the torque-angular velocity relationship differently in older compared with young men. Neuromuscular properties were recorded from 10 young (~25 y) and 10 old (~78 y) men with the knee extended (170°) and flexed (90°), in a randomized order. Participants performed maximal voluntary isometric contractions (MVCs), followed by maximal velocity-dependent shortening contractions at pre-set loads, ranging from 15 to 75% MVC. The young men were ~20-25% stronger, ~12% faster and ~30% more powerful than the old for both knee angles (P<0.05). In both age groups, isometric MVC torque was ~17% greater in the extended than flexed knee position, with no differences in voluntary activation (>95%). The young men produced 7-12% faster angular velocities in the extended knee position for loads ≤30% MVC, but no differences at higher loads; whereas there were no detectable differences in angular velocity between knee positions in the old across all relative loads. For both knee angles, young men produced peak power at 43.3±9.0% MVC, whereas the old men produced peak power at 54.8±7.9% MVC. These data indicate that the young, who have faster contracting muscles compared with the old, can rely more on velocity than torque for generating maximal power.

Prediction of the muscle strength by the muscle thickness and hardness using ultrasound muscle hardness meter

PURPOSES

The present study investigated whether a combination of the thickness and hardness of muscles without muscle tension can be used to estimate muscle strength during knee extension in adult males and females.

METHODS

Seventy-two males and thirty-three females, whose ages ranged from 18 to 35 years, participated in this study. We measured muscle thickness and hardness in the right anterior region of the thigh (rectus femoris muscle and vastus intermedius muscle) without muscle tension using an ultrasound muscle hardness meter, and the maximal voluntary isometric contraction of right knee extension (MVIC). The changing ratios (%) of the tissue thickness before compression to those during compression (compression ratio) are calculated as an index of the hardness. Higher ratio indicates a harder muscle compared with that of other individuals showing the same muscle thickness.

RESULTS

In male group, although the MVIC had significantly positive correlation to both muscle thickness (r=0.412, p<0.01) and compression ratio (r=0.233, p<0.05), their variables also had correlation mutually. In the female group, the MVIC has significantly positive correlation to only compression ratio (r=0.499, p<0.01), not muscle thickness (r=0.225, n.s.). On multiple linear regression analysis, the combination of two parameters (muscle thickness and compression ratio) allowed more accurate estimation of MVIC (r=0.573, p<0.01) in the female group.

CONCLUSION

These findings suggested that the combination of muscle thickness and hardness is capable of effectively estimating muscle strength especially in females.

Effect of whole body vibration training on mobility in children with cerebral palsy: a randomized controlled experimenter-blinded study

Objective:

To evaluate ambulatory function and leg muscle thickness after whole body vibration training in children with cerebral palsy.

Design:

A block randomized controlled trial with two groups.

Setting:

Physical therapy department laboratory.

Subjects:

A total of 30 (15 experimental, mean (SD) age 10.0 (2.26) years and 15 control, 9.6 (2.58)) children with cerebral palsy, 15 males and 15 females.

Interventions:

The experimental group underwent whole body vibration training combined with conventional physical therapy training; the control group underwent conventional physical therapy training three days a week for eight weeks respectively.

Main outcome measures:

Three-dimensional gait analyses and ultrasonographic imaging of the leg muscles were measured at pre- and post-test of intervention for eight weeks.

Results:

Whole body vibration training resulted in significantly better gait speed ( P = 0.001, from 0.37 (0.04) m/s to 0.48 (0.06)), stride length ( P = 0.001, from 0.38 (0.18) m to 0.48 (0.18)) and cycle time ( P = 0.001, from 0.85 (0.48) s to 0.58 (0.38)) in the experimental group compared with that in the control group. The ankle angle ( P = 0.019, from 7.30 (4.02) degree to 13.58 (8.79)) also showed a remarkable increase in the experimental group, but not the hip ( P = 0.321) and knee angle ( P = 0.102). The thicknesses of the tibialis anterior ( P = 0.001, 0.48 (0.08) mm to 0.63 (0.10)) and soleus ( P = 0.001, 0.45 (0.04) mm to 0.63 (0.12)) muscles were significantly higher in the experimental group than in the control group. However, no significant effect was observed in the thickness of the gastrocnemius muscle ( P = 0.645).

Conclusions:

These findings suggest that whole body vibration may improve mobility in children with cerebral palsy, probably through a positive effect on the leg muscles.

Neuromuscular determinants of maximum walking speed in well-functioning older adults

Maximum walking speed may offer an advantage over usual walking speed for clinical assessment of age-related declines in mobility function that are due to neuromuscular impairment. The objective of this study was to determine the extent to which maximum walking speed is affected by neuromuscular function of the lower extremities in older adults. We recruited two groups of healthy, well functioning older adults who differed primarily on maximum walking speed. We hypothesized that individuals with slower maximum walking speed would exhibit reduced lower extremity muscle size and impaired plantarflexion force production and neuromuscular activation during a rapid contraction of the triceps surae muscle group (soleus (SO) and gastrocnemius (MG)). All participants were required to have usual 10-meter walking speed of >1.0m/s. If the difference between usual and maximum 10m walking speed was <0.6m/s, the individual was assigned to the "Slower" group (n=8). If the difference between usual and maximum 10-meter walking speed was >0.6m/s, the individual was assigned to the "Faster" group (n=12). Peak rate of force development (RFD) and rate of neuromuscular activation (rate of EMG rise) of the triceps surae muscle group were assessed during a rapid plantarflexion movement. Muscle cross sectional area of the right triceps surae, quadriceps and hamstrings muscle groups was determined by magnetic resonance imaging. Across participants, the difference between usual and maximal walking speed was predominantly dictated by maximum walking speed (r=.85). We therefore report maximum walking speed (1.76 and 2.17m/s in Slower and Faster, p<.001) rather than the difference between usual and maximal. Plantarflexion RFD was 38% lower (p=.002) in Slower compared to Faster. MG rate of EMG rise was 34% lower (p=.01) in Slower than Faster, but SO rate of EMG rise did not differ between groups (p=.73). Contrary to our hypothesis, muscle CSA was not lower in Slower than Faster for the muscle groups tested, which included triceps surae (p=.44), quadriceps (p=.76) and hamstrings (p=.98). MG rate of EMG rise was positively associated with RFD and maximum 10m walking speed, but not the usual 10m walking speed. These findings support the conclusion that maximum walking speed is limited by impaired neuromuscular force and activation of the triceps surae muscle group. Future research should further evaluate the utility of maximum walking speed for use in clinical assessment to detect and monitor age-related functional decline.

Effects of regular heel-raise training aimed at the soleus muscle on dynamic balance associated with arm movement in elderly women

The effects of low-intensity muscle training with heel-raises on dynamic balance associated with bilateral arm flexion were investigated in postmenopausal elderly women. Twenty-six elderly women were evenly grouped into training and control groups. Training group subjects performed 100 heel raises per day for 2 months. The training was aimed at hypertrophy of the soleus muscle, which has a relatively high proportion (ca. 90%) of slow-twitch muscle fibers and is one of the main postural muscles. Dynamic balance was measured while arm flexion was performed in response to a visual stimulus (simple-reaction condition) or at the subjects' own pace (own-timing condition). The following parameters were compared before and after the training period: plantar flexion strength, thicknesses of the gastrocnemius and soleus (by ultrasound), reaction time of the anterior deltoid in the simple-reaction condition, activation onset timing of postural muscles with respect to the deltoid, movement angles of ankle and hip joints, and postural fluctuation. In the training group only, the following training-related effects were demonstrated: (a) increase in plantar flexor strength and thickness of the soleus, (b) shortening of the deltoid reaction time, (c) earlier activation of the erector spinae in the simple-reaction condition and the soleus in the own-timing condition, and (d) increase in ankle movement in the own-timing condition and a decrease in postural fluctuation. This heel-raise training in the elderly can increase soleus thickness within the triceps surae and improve postural control modality and stability that are effectively contributed to by the leg muscle. This training consists of a low-intensity exercise that requires neither special machines nor a specific environment and can be performed safely for all old-aged groups.

Effects of age and inactivity due to prolonged bed rest on atrophy of trunk muscles

This study investigated the effects of age and inactivity due to being chronically bedridden on atrophy of trunk muscles. The subjects comprised 33 young women (young group) and 41 elderly women who resided in nursing homes or chronic care institutions. The elderly subjects were divided into two groups: independent elderly group who were able to perform activities of daily living involving walking independently (n = 28) and dependent elderly group who were chronically bedridden (n = 13). The thickness of the following six trunk muscles was measured by B-mode ultrasound: the rectus abdominis, external oblique, internal oblique, transversus abdominis, thoracic erector spinae (longissimus) and lumbar multifidus muscles. All muscles except for the transversus abdominis and lumbar multifidus muscles were significantly thinner in the independent elderly group compared with those in the young group. The thicknesses of all muscles in the dependent elderly group was significantly smaller than that in the young group, whereas there were no differences between the dependent elderly and independent elderly groups in the muscle thicknesses of the rectus abdominis and internal oblique muscles. In conclusion, our results suggest that: (1) age-related atrophy compared with young women was less in the deep antigravity trunk muscles than the superficial muscles in the independent elderly women; (2) atrophy associated with chronic bed rest was more marked in the antigravity muscles, such as the back and transversus abdominis.

Atrophy of the lower limbs in elderly women: is it related to walking ability?

This study investigated the relationship between walking ability and age-related muscle atrophy of the lower limbs in elderly women. The subjects comprised 20 young women and 37 elderly women who resided in nursing homes or chronic care institutions. The elderly subjects were divided into three groups according to their walking ability. The muscle thickness of the following ten lower limb muscles were measured by B-mode ultrasound: the gluteus maximus, gluteus medius, gluteus minimus, psoas major, rectus femoris, vastus lateralis, vastus intermedius, biceps femoris, gastrocnemius and soleus. Compared to the young group, muscle thicknesses of all muscles except the soleus muscle were significantly smaller in all the elderly groups. There were no significant differences between the fast- and slow-walking groups in the thickness of any muscle. In the dependent elderly group, noticeable muscle atrophy was observed in the quadriceps femoris muscle. The results of this study suggest that the elderly who are capable of locomotion, regardless of their walking speed, show a moderate degree of age-related atrophy, while those who do not walk exhibit more severe atrophy, especially in the quadriceps femoris muscle.

Power loss is greater in old men than young men during fast plantar flexion contractions

It is unclear during human aging whether healthy older adults (>70 yr old) experience greater, lesser, or the same fatigability compared with younger adults. The reported disparate findings may be related to the task-dependent nature of fatigue and the limited number of studies exploring nonisometric contractile function and aging. The purpose here was to determine the effects of fast shortening contractions on the fatigability of the triceps surae in 10 young (~24 yr old) and 10 old (~78 yr old) men using isometric and dynamic measures. Participants performed 50 maximal velocity-dependent plantar flexions at a constant load of 20% maximal voluntary isometric contraction (MVC). Isometric twitch properties and MVCs were tested at baseline and during and following the fatigue task. Voluntary activation was similar between the old and young (~98%) and was unaltered with fatigue. The old had 26% lower (P < 0.01) isometric MVC torque and 18% slower (P < 0.01) maximal shortening velocity than the young. Hence, peak power was 38% lower in the old (P < 0.01). At task termination, MVC torque was maintained in the old (P = 0.15) but decreased by 21% in the young (P < 0.01). Twitch half-relaxation time was lengthened in the old at task termination by 26% (P < 0.01) but unchanged in the young (P = 0.10). Peak power was reduced by 24% and 17% at task termination in the old and young, respectively (P < 0.01). Despite a better maintenance in isometric MVC torque production, the weaker and slower contracting triceps surae of the old was more fatigable than the young during fast dynamic efforts with an unconstrained velocity.