Differences in size, strength, and power of upper and lower body muscle groups in young and older men

We compared muscle thickness, torque, normalized torque (torque/muscle thickness), and power at 1.05 rad/s and 3.14 rad/s in flexor and extensor muscles of the elbow and knee, and in ankle plantar flexors in young (n=22, 18-31 years) and older (n=28, 59-76 years) men. Young men had greater muscle thickness for all muscle groups (p<.01), except elbow extensors, which were similar to older men. Young men had greater torque and power at both velocities for all muscle groups (p<.01), and greater normalized torque at both velocities for the elbow extensors and knee flexors and at the fast velocity for knee extensors. Relative to young mean values, muscle thickness, and torque, normalized torque, and power in the older group were most affected for lower-body measurements, especially at the fast velocity. Torque, normalized torque, and power (especially at fast velocities), and muscle thickness in the lower body are affected more by aging than are upper body measures in men.     

Skeletal muscle contractile characteristics and fatigue resistance in patients with chronic heart failure

Whole muscle contractile characteristics and fatigue resistancewere studied in male patients with chronic heart failure (n=6)and in healthy control subjects (n=6). Maximum voluntary isometricstrength in the major muscle groups of leg (plantar flexorsand knee extensors) and arm (elbow extensors and elbow flexors),was found to be similar for both groups of subjects. However,a faster isometric twitch time course was observed in the plantarflexor and knee extensor muscles of heart failure chronic patients.The poor resistance to fatigue in the knee extensors of chronicheart failure patients was confirmed in the present study, butusing twitch interpolation this was shown not to be due to pooractivation. The plantar flexors of chronic heart failure patientsalso showed a tendency to be less resistance to fatigue, evenwhen the muscle was activated by direst electrical stimulation. The present study shows that independent of muscle strength,patients with chronic heart failure may possess muscles thatare faster to contract and less resistant to fatigue. However,it seems this increased fatigability is not due to poor muscleactivation.     

Eccentric knee strength of elderly females

This study compared the strength of the knee extension and flexion muscles in groups of young and elderly women under two conditions: eccentric exercise in which the muscles were lengthened while subjects tried to resist an external force, versus concentric contractions in which the muscles shortened. Twenty-six females, aged 20 to 29 (Mean 25 +/- 3 SD), and 26 elderly women, aged 66 to 89 (Mean 73 +/- 6 SD), were tested at two angular velocities of movement, 45 degrees and 90 degrees/s, on a KinCom isokinetic dynamometer. Elderly women had significantly lower peak and average torque values in all comparisons with the young female group (25 to 54% lower, p less than .01). However, differences between the age groups were consistently smaller for the eccentric type of muscle action than the concentric, in both knee extensors and flexors.     

Relationships among age-associated strength changes and physical activity level, limb dominance, and muscle group in women

This study investigated the magnitude and rate of age-associated strength reductions in Australian independent urban-dwelling women and the relationship to muscle groups, limb dominance, and physical activity level. Independent urban-dwelling women aged 20 to 89 years (N = 217) performed maximal voluntary contractions with the dominant and nondominant knee extensors, plantar flexors, and handgrip. Anthropometric measurements were made and questionnaire responses used to obtain current physical activity levels. Trend analysis within analysis of variance and regression analysis on strength was performed. Limb muscle strength was found to be associated with increased age, muscle group, limb dominance, and activity. Self-reported physical activity levels declined with age but women who were more physically active for their age group were stronger in all muscle groups and had more lean body mass and lean thigh and leg cross-sectional area than relatively inactive women. Slopes of the linear reductions of maximal voluntary strength of the knee extensors, plantar flexors, and handgrip with age were significantly different (p < .05) at 9.3%, 7.4%, and 6.2% per decade, respectively. The limb muscle strength of healthy Australian independent and urban-dwelling women aged 20 to 89 years was found to be associated with age and three aspects of disuse: muscle group, relative levels of physical activity, and limb dominance.     

Comparison of muscle strength and in-vivo muscle morphology in young children with haemophilia and those of age-matched peers

Recent advances in imaging have enhanced our understanding of the morphological adaptations of muscle in response to disease and altered use. Adaptation in muscle morphology has been linked to changes in muscle strength. To date, no studies have compared muscle morphology and strength in young children with haemophilia to that of typically developing children. This study explored differences in muscle strength and morphology between typically developing and age and size-matched boys aged 6-12 years with haemophilia and a history of recurrent haemorrhage in the ankle joint. Maximum muscle strength of the knee flexors (KF), extensors (KE), ankle dorsi (ADF) and plantar flexors (APF) was measured in 19 typically developing boys (Group 1) and 19 boys with haemophilia (Group 2). Ultrasound images of vastus lateralis (VL) and lateral gastrocnemius (LG) were recorded to determine muscle cross-sectional area (CSA), thickness, width, fascicle length and pennation angle. Muscle strength of the KE, ADF and APF were significantly (P < 0.05) lower in Group 2 when compared with Group 1. Muscle CSA and width of VL were significantly smaller and pennation angles significantly larger in Group 2 (P < 0.05). Muscle CSA and thickness of LG were significantly (P < 0.05) smaller in Group 2. Linear regression showed that LG muscle CSA and thickness were significant (P < 0.01) predictors of APF muscle strength. Following ankle joint bleeding in young boys with haemophilia, secondary adaptations in muscle strength and morphology were observed, suggesting that muscle function is more impaired than current clinical evaluations imply.     

The relationship between the leg muscle strength and physical capacity in patients with rheumatoid arthritis, with reference to the influence of corticosteroids

It has been shown that patients with rheumatoid arthritis have weak muscles, especially when they are treated with corticosteroids. Forty-six female patients suffering from rheumatoid arthritis were evaluated with regard to the physical capacity in the lower legs by measuring the walking speed and the climbing performance as correlated to the isokinetic muscle strength of the knee extensors and the plantar flexors. Twenty-six of the patients (average age 60 years, range 34-76) had been treated with corticosteroids. Twenty patients (average age 58 years, range 31-72) had never received corticosteroids. The mean maximal isokinetic muscle strength of the knee extensors in corticosteroid treated patients was 62 +/- 28 Nm (SD) at the angular velocity 30 degrees/s, and the mean maximal isokinetic muscle strength of the plantar flexors in the same group of patients was 33 +/- 21 Nm (SD) at the same angular velocity. Compared to patients with rheumatoid arthritis who had never been treated with corticosteroids the reduction in muscle strength was 37% and 28%, respectively (p less than 0.001 and p less than 0.01). The mean walking speed in patients with corticosteroid treatment was 0.9 m/s, which was a 36% reduction as compared with that found in patients who had not received corticosteroids (p less than 0.01). Half of the patients who had not received corticosteroids were able to climb a 50 cm step, while this was possible in only 16% of the group of corticosteroid-treated patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Knee extensor and knee flexor strength: cross-sectional area ratios in young and elderly men.

The relationships between isometric and isokinetic-concentric knee extensor and knee flexor strength, and quadriceps and hamstring cross-sectional area (CSA) were determined in young (n = 13, M = 24.5y) and elderly (n = 12, M = 70.7y) men. Quadriceps and hamstring CSA was determined by computed tomography. Knee extensor and flexor strength at 0 degree/s and 120 degree/s was determined on a Kin-Com isokinetic dynamometer. Compared to the young men, elderly men had significantly smaller quadriceps muscles and were weaker (22-32%) in knee flexion and knee extension at both angular velocities. Strength:CSA ratios were similar at 0 degree/s, but elderly men had decreased ratios for both extensors and flexors at 120 degree/s. Correlations of knee extensor and flexor strength with muscle CSA were significant at both velocities in elderly men, but not at either velocity for the knee flexors in young men. The decrease in isometric strength in elderly men can be accounted for by their decrease in muscle CSA, but their decrease in isokinetic-concentric strength was greater than their loss of CSA. Further study is required to determine the reason for this nonproportional loss of isokinetic-concentric strength.     

Isokinetic and isometric muscle strength in patients with rheumatoid arthritis. The relationship to clinical parameters and the influence of corticosteroid

The isometric and isokinetic muscle strength of the legs in forty-six women with rheumatoid arthritis was measured using a Cybex II dynamometer. Twenty-six of the patients had been treated with corticosteroid - prednisone - some for several years (mean 8 years, range 1-35). Twenty-three healthy age-matched women served as a comparable group (controls). In patients treated with prednisone the mean maximal isokinetic muscle strength of the knee extensors was between 64 +/- 26 Nm (SD) and 43 +/- 18 Nm (SD) at the preset angular velocities 30 degrees/s and 180 degrees/s, respectively, which was a reduction to 54%-55% of that found in controls (p less than 0.001). In patients who had not received prednisone the mean maximal isokinetic strength was between 99 +/- 39 Nm (SD) and 67 +/- 27 Nm (SD) which was a reduction to 84%-86% of that found in controls (p less than 0.05). The force velocity curve showed a parallel decrease in maximal strength with increasing velocity when comparing patients with rheumatoid arthritis to controls. Also on measuring the isokinetic muscle strength of plantar flexors a significantly lower mean maximal torque was found in patients treated with prednisone, (33 +/- 21 Nm (SD) (p less than 0.01] as compared with a control group (50 +/- 28 Nm (SD]. The patients who had not been treated with prednisone showed a lower, but not significantly lower isokinetic strength of the plantar flexors, 46 +/- 22 Nm (SD) at a corresponding angular velocity, 30 degrees/s.(ABSTRACT TRUNCATED AT 250 WORDS)     

The relationship of knee and ankle weakness to falls in nursing home residents: an isokinetic study

The strength of the knees and ankles of a group of nursing home residents with a history of falls was compared to age-matched controls. Peak torque (PT) and power (POW) were recorded at two limb velocities (60 degrees/s and 120 degrees/s) on a Cybex II Isokinetic dynamometer for four muscle groups: knee extensors, knee flexors, ankle plantar flexors and ankle dorsiflexors. The PT and POW of fallers were significantly decreased for all four muscle groups in comparison to controls, with the ankles showing the greatest decrements. Although POW in fallers was significantly lower at the higher velocity in both joints, the decrease was most prominent in the ankles. Dorsiflexion POW production in fallers was the most affected of all the motions (7.5 times less than the control value). At the higher, more functional limb velocities, ankle weakness particularly involving the dorsiflexors appears to be an important factor underlying poor balance.     

The effect of age and joint angle on the proportionality of extensor and flexor strength at the knee joint

Functional movements require concerted actions of monoarticular and biarticular agonists and antagonists. Understanding age-related changes of muscle function on performance requires insight in the contributions of different muscles to joint moments. Young and elderly participants performed isometric knee extensions and flexions at combinations of knee and hip joint angles. This approach allowed assessing changes in contribution of monoarticular and biarticular knee joint flexors and extensors. Reduced moments were found for elderly persons (flexors: -43%; extensors: -33%). In the flexor group, this reduction was mainly caused by retardation of the biarticular muscles; in the extensors, by reduced strength of the monoarticular muscles. This age-related reduction of joint moments occurred to be joint angle dependent for the extensors. In the flexor group, the reduction was almost invariant. Due to this difference in joint angle dependence, the proportionality between extensors and flexors varied over joint angles and differed with age. It has been discussed how this is related to changes in performances occurring with age.     

Effects of long-term resistive training on mobility and strength in older adults with diabetes

BACKGROUND: Strength training has been shown to be beneficial in older adults. However, very little data exist on the effects of strength training in older diabetics. METHODS: 31 community-dwelling older adults with diabetes (mean age = 66.1 years) were randomly assigned to either an exercise (EX) or control (CO) group. The EX group trained the plantar flexors, knee extensors, knee flexors, hip extensors, and hip flexors muscle groups at 50%, 60%, and 70% of 1-repetition maximum, 2.6 days a week, for 24 months. Mobility tests included the timed up and go, 50-foot walk, and walking up and down 8 stairs. Strength and mobility for both groups were evaluated at 6-month intervals. RESULTS: There was a group and time effect as the EX group increased 31.4% (p <.001) in strength for all muscle groups after the first 6 months of training, and the strength gains were retained for the duration of the training intervention. There was also a group and time effect for mobility as performance increased 8.6% and 9.8% (p =.032 and p = 0.031) for the first 6 and 12 months, respectively, but decreased to 4.6% above baseline at the end of the intervention. There were essentially no changes from baseline strength or mobility values for the CO group. CONCLUSION: In conclusion, these data suggest that a moderate-intensity resistive-training program can improve mobility and strength for the duration of a 24-month intervention in older adults with diabetes, thus potentially reducing the rate of mobility loss during aging.     

Muscle-tendon tissue properties in the hypermobility type of Ehlers-Danlos syndrome

Objective

To investigate the passive properties of the plantar flexors muscle–tendon tissue in patients with the hypermobility type of Ehlers‐Danlos syndrome (EDS‐HT).

Methods

Twenty‐five women with EDS‐HT and 25 sex‐ and age‐matched healthy control subjects participated in the study. Passive resistive torque (PRT) of the plantar flexors was measured with an isokinetic dynamometer during 2 standardized stretch protocols to obtain the passive muscle tension. Protocol 1 consisted of 4 continuous cycles to a predetermined angle of 10° dorsiflexion. Protocol 2 consisted of a slow stretch to the onset of pain. Torque, angle, and electromyography were simultaneously recorded during the tests. To take muscle thickness into account, muscle cross‐sectional area (MCSA) was obtained with peripheral quantitative computed tomography. Stiffness of the Achilles tendon was assessed using a dynamometer in combination with ultrasonography.

Results

The results demonstrate a significantly larger maximal joint angle in the EDS‐HT patients accompanied by a similar PRT compared to the control subjects (protocol 2), indicating a lower passive muscle tension in the patient group. PRT for the predetermined angle (protocol 1) was the same for both groups and there was no difference in MSCA. Furthermore, a significantly lower Achilles tendon stiffness was seen in the patient group than in the control group.

Conclusion

This study is the first to provide evidence for altered passive properties of the muscle–tendon unit in EDS‐HT patients. These changes are thought to be associated with structural modifications in connective tissue.     

Influence of ankle plantar flexor muscle architecture and strength on gait in boys with haemophilia in comparison to typically developing children

Altered gait patterns, muscle weakness and atrophy have been reported in young boys with severe haemophilia when compared to unaffected peers. The aim of this study was to determine whether lateral gastrocnemius muscle size and architecture influenced biomechanical walking patterns of boys with haemophilia and if these relationships differed from age‐matched typically developing boys. Biomechanical function of the knee and ankle during level walking, lateral gastrocnemius anatomical cross‐sectional area, thickness, width, fascicle length and pennation angle and ankle plantar flexor muscle strength were recorded in 19 typically developing boys aged 7–12 years and 19 age‐matched haemophilic boys with a history of ankle joint bleeding. Associations between gait, strength and architecture were compared using correlations of peak gait values. Haemophilic boys walked with significantly larger (P < 0.05) ankle dorsi flexion angles and knee flexion moments. The ankle plantar flexor muscles of haemophilic boys were significantly weaker and smaller when compared to typically developing peers. In the typically developing boys there was no apparent association between muscle architecture, strength and walking patterns. In haemophilic boys maximum muscle strength and ACSA normalized torque of the ankle plantar flexors together with the muscle width, thickness, fascicle length and angulation (P < 0.05) were associated with motion at the ankle and peak moments at the knee joint. Muscle strength deficits of the ankle plantar flexors and changes in muscle size and architecture may underpin the key biomechanical alterations in walking patterns of haemophilic boys with a history of ankle joint bleeding.     

Muscle function and functional ability improves more in community-dwelling older women with a mixed-strength training programme

BACKGROUND: Supervised training can reach a limited number of elderly people. OBJECTIVE: To determine the impact of a 1-year mixed-strength training programme on muscle function (MF), functional ability (FA) and physical activity (PA). SETTING: Twice-a-week hospital-based exercise classes and a once-a-week home session. Participants: twenty-eight healthy community-dwelling men and women on the training programme and 20 controls aged over 75 years. METHODS: Training with two multi-gym machines for the lower limbs at 60% of the repetition maximum (1RM). At-home subjects used elastic bands. MEASUREMENTS: Maximum isometric strength of knee extensors (KE), ankle plantar flexors (PF), leg extensor power (LEP), functional reach (FR), chair rise 1 (CR1) and 10 times (CR10), bed rise (BR), six-minute walking test (6MWT), stair climbing (SC), get-up-and-go (GU&G), one-leg standing (1LS). PA was assessed with the Paqap questionnaire. RESULTS: Women were significantly weaker than men at baseline: -47% for KE and -59% for PF. Training induced significant gains in MF and FA in the training females; males improved significantly only in FA. PA levels increased non-significantly (2%) in all of the training group. CONCLUSIONS: Long-term mixed-strength programmes can improve MF and FA in elderly females, and FA in elderly males.     

Effects of a one-year exercise training program in adults over 70 years old: a study with a control group

BACKGROUND AND AIMS: Exercise training is known to improve exercise tolerance in elderly subjects. Therefore the present study aimed at investigating the effects of one year of combined endurance and resistance training in healthy older people. METHODS: After baseline evaluation, subjects were assigned to either the training group (n=24, age 77.2+/-3.6) or the control group (n=16, age 76.1+/-4.8). Subjects in the control group did not change anything in their everyday activities, whereas subjects in the training group underwent moderately intensive combined exercise training, 3 hours a week over the course of one year. Breath-by-breath oxygen uptake and heart rate were measured at each workload during the symptom-limited cardiopulmonary exercise test. Performance on the 6-minute (6-MWT) and 200-meter (200-MWT) walk tests was registered and maximal strength was measured on knee extensor and plantar flexor muscles. RESULTS: After training, oxygen uptake was significantly increased, both at the ventilatory threshold (+11.6%, p<0.01) and at the end of exercise (+14.8%, p<0.001). The distance walked in 6 min (+10%, p<0.001), the time required to cover 200 m (-7.3%, p<0.001) and the maximal muscle strength (+15.2% and +17.4% for knee extensors and plantar flexors respectively, p<0.05) also improved after training. All these parameters had not significantly changed in the control group after the one-year period. CONCLUSIONS: The results of the present study show that one year of combined exercise training is well-tolerated and improves aerobic capacity, performance on field tests and muscle strength in healthy subjects over 70 years old.     

An investigation of the association between grip strength and hip and knee joint moments in older adults

Grip strength is a predictor of health outcomes but with differing rates of age-related decline in muscle strength, it is unclear whether handgrip is a reliable indicator of lower limb moments. This study investigated the relationship between grip strength and lower extremity moments in community-dwelling older adults. Eighty-two healthy volunteers aged 60-82 years (mean age 73.2 years) performed maximal voluntary contractions of knee and hip extensors and flexors at three positions and at neutral position for hip abductors and adductors using a custom-built dynamometer. Grip strength was measured using an electronic Jamar dynamometer. The relative reduction in muscle strength of 80s age category compared to 60-year-olds ranged from 14% for grip strength to 27% for hip abductors. Peak torque of flexors and extensors of the knee and hip joints were significantly correlated with grip strength and Pearson's correlation coefficients ranged from 0.56 to 0.78 with the highest correlations observed between knee moments and grip strength. "Good" correlation was found but only 31-60% of the variation in grip strength could be related to changes in joint torques. Hence the assumption that grip strength is an indicator of strength in the lower limb would seem unjustified in the healthy older adult.     

Neuromechanical properties of the triceps surae in young and older adults

The aim of this study was to compare voluntary and involuntary force generating capacity of the triceps surae muscles in healthy young and older adult participants during isometric and isokinetic contractions. Ultrasound was used to measure medial gastrocnemius (MG) fascicle length during maximal voluntary isometric contractions and supra-maximal isometric twitch contractions at five ankle angles throughout the available range of motion, as well as isokinetic concentric and eccentric contractions at four ankle velocities. Maximum voluntary activation of the plantar flexors was assessed using the twitch interpolation technique. Peak plantar flexor torque was significantly lower in older adults compared to young participants by 42%, 28% and 43% during maximal voluntary isometric contractions, supra-maximal isometric twitch and concentric contractions respectively. No age-related differences in eccentric torque production were detected. When age-related differences in triceps surae muscle volume determined from MRI were taken into account, the age-related peak plantar flexor torque deficits for maximum voluntary isometric, supra-maximal twitch, and concentric contractions were 24%, 19% and 24% respectively. These age-related differences in torque were not explained by torque–length–velocity behaviour of the MG muscle fascicles, passive plantar flexor torque–angle properties, decreased neural drive of the plantar flexor muscles or antagonistic co-activation of the tibialis anterior muscle. The residual deficit in isometric and concentric plantar flexor torques in healthy older adults may involve reduced muscle quality. A significant reduction in supra-maximal twitch torque at longer MG fascicle lengths as well as a lower MG fascicle velocity during eccentric contractions in older adults was detected, which could possibly be a function of the reported increased Achilles tendon compliance in older adults.     

MUSCLE STRENGTH IN HEALTHY PEOPLE AND IN PATIENTS SUFFRING FROM RECENT-ONSET INFLAMMATORY ARTHRIRIS

Neuromuscular function was compared among 20 patients with relativelyrecent onset (symptomatic period 17 ± 24 months) rheumatoidarthritis (RA) (experimental group; EG), and 20 age- and sex-matchedhealthy people (control group; CG).The comparison was repeatedafter a period of 6 months, when 16 patients had carried outprogressive strength training. At baseline maximal grip strengthand maximal dynamic unilateral strength of the knee extensorsin the EG were significantly (P < 0.05) lower in comparisonto the CG. The groups did not differ from each other in maximalisometric strength of the trunk flexors and extensors or theknee extensors. The 6-month dynamic strength training in theEG resulted in significant increases in maximal dynamic strengthof the knee extensors (P < 0.001), in isometric grip strength(P < 0.001) and in isometric strength of the trunk flexors(P < 0.05) and extensors (P < 0.05) to the level of thehealthy controls. Only minor changes took place in explosivestrength and maximal isometric strength of the knee extensors.Erythrocyte sedimentation rate (P < 0.001), Ritchie's articularindex (P < 0.01) and modified health assessment questionnaire(P < 0.01) improved significantly during the training period.The results suggest that inflammatory arthritis decreases dynamicand/or isometric muscle strength in selected muscle groups ofthe body already in the early stages of disease. However, progressivedynamic strength training rapidly increases the neuromuscularperformance capacity of the patients even to the level of healthypeople without detrimental effects on disease activity. KEY WORDS: Recent-onset inflammatory arthritis, Muscle strength, Neuromuscular function, Strength training, Disease activity, Healthy people     

The unreliability of clinical measures of muscle tone: implications for stroke therapy

BACKGROUND: the central tenet of the neurofacilitatory approach to stroke therapy is that muscle tone needs to be normal before normal movement can occur. A reliable clinical measure of the full spectrum of muscle tone is needed to test: (i) the purported relationship between muscle tone, other motor impairments and disability, and (ii) the effectiveness of stroke therapy to restore movement. AIM: the purpose of the study was to test the inter-rater reliability of clinical categorization of muscle tone (spastic/normal/flaccid) and also a visual analogue scale with anchor points of 'lowest tone possible' (score 0) and 'highest tone possible' (score 100). METHODS: four independent raters assessed tone of elbow flexors and knee extensors of 14 stroke rehabilitation inpatients using the categorical scale. Six independent raters assessed tone of elbow flexors and knee extensors of 25 chronic stroke patients and two healthy volunteers using the visual analogue scale. All assessment orders were randomized. RESULTS: both scales were unreliable, with K coefficients for the categorical scale ranging from -0.046 to 0.56 for the categorical scale, and intra-class correlation coefficients for the visual analogue scale of 0.595 for elbow flexors and 0.451 for knee extensors. Assessment order effects for the visual analogue scale were non-significant for elbow flexors (P= 0.545) and knee extensors (P= 0.911). CONCLUSIONS: these results, and those of earlier studies, suggest that clinical measures of muscle tone are consistently unreliable. Systematic investigation of the therapy rationale for planning and evaluating treatment is required before relevant clinical measures can be developed.     

Longitudinal muscle strength changes in older adults: influence of muscle mass, physical activity, and health

The longitudinal changes in isokinetic strength of knee and elbow extensors and flexors, muscle mass, physical activity, and health were examined in 120 subjects initially 46 to 78 years old. Sixty-eight women and 52 men were reexamined after 9.7 +/- 1.1 years. The rates of decline in isokinetic strength averaged 14% per decade for knee extensors and 16% per decade for knee flexors in men and women. Women demonstrated slower rates of decline in elbow extensors and flexors (2% per decade) than men (12% per decade). Older subjects demonstrated a greater rate of decline in strength. In men, longitudinal rates of decline of leg muscle strength were approximately 60% greater than estimates from a cross-sectional analysis in the same population. The change in leg strength was directly related to the change in muscle mass in both men and women, and it was inversely related to the change in medication use in men. Physical activity declined yet was not directly associated with strength changes. Although muscle mass changes influenced the magnitude of the strength changes over time, strength declines in spite of muscle mass maintenance or even gain emphasize the need to explore the contribution of other cellular, neural, or metabolic mediators of strength changes.