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.     

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.     

Lower extremity power training in elderly subjects with mobility limitations: a randomized controlled trial

BACKGROUND AND AIMS: This study investigated whether high-velocity high-power training (POW) improved lower extremity muscle power and quality in functionally-limited elders greater than traditional slow-velocity progressive resistance training (STR). METHODS: Fifty-seven community-dwelling older adults aged 74.2+/-7 (range 65-94 yrs), Short Physical Performance Battery score 7.7+/-1.4, were randomized to either POW (n=23) (12 females), STR (n=22) (13 females) or a control group of lower extremity stretching (CON) (n=12) (6 females). Training was performed three times per week for 12 weeks and subjects completed three sets of double leg press and knee extension exercises at 70% of the one repetition maximum (1RM). Outcome measures included 1RM strength and peak power (PP). Total leg lean mass was determined using dual-energy X-ray absorptiometry to estimate specific strength and specific PP. RESULTS: During training, power output was consistently higher in POW compared to STR for knee extension (approximately 2.3-fold) and leg press (approximately 2.8-fold) exercises (p<0.01). Despite this, PP and specific PP of the knee extensors increased similarly from baseline in POW and STR compared to CON (p<0.01), and no significant time-group interaction occurred for PP of the leg extensors. However, gains in leg press specific PP were significantly greater in POW compared to both STR and CON (p<0.05). Total leg lean mass did not change within any group. CONCLUSIONS: A short-term intervention of high-velocity power training and traditional slow-velocity progressive resistance training yielded similar increases of lower extremity power in the mobility-impaired elderly. Neuromuscular adaptations to power training, rather than skeletal muscle hypertrophy, may have facilitated the improvements in muscle quality. Additional studies are warranted to test the efficacy of power training in older individuals with compromised physical functioning.     

High-velocity resistance training increases skeletal muscle peak power in older women

OBJECTIVES: Peak power declines more precipitously than strength with advancing age and is a reliable measure of impairment and a strong predictor of functional performance. We tested the hypothesis that a high-velocity resistance-training program (HI) would increase muscle power more than a traditional low-velocity resistance-training program (LO). DESIGN: Randomized controlled trial. SETTING: University-based human physiology laboratory. PARTICIPANTS: Thirty women with self-reported dis-ability (aged 73 + 1, body mass index 30.1 + 1.1 kg/mn). INTERVENTION: We conducted a randomized trial comparing changes in skeletal muscle power and strength after 16 weeks of HI or LO. Training was performed three times per week, and subjects completed three sets (8-10 repetitions) of leg press (LP) and knee extension (KE) exercises at 70% of the one-repetition maximum (IRM). MEASUREMENTS: One-repetition maximum (1 RM) and peak power for KE and LP. RESULTS: LP and KE relative training force and total work were similar between groups (P > .05). However, HI generated significantly higher power during training sessions than LO for LP (3.7-fold greater, P < .001) and KE (2.1-fold greater, P < .001). Although LP and KE 1RM muscle strength increased similarly in both groups asa result of the training (P < .001), LP peak power increased significantly more in HI than in LO (267 W vs 139 W, P < .001). Furthermore, HI resulted in a significantly greater improvement in LP power at 40%, 50%, 60%,70%, 80%, and 90% of the 1 RM than did LO (P <.05).CONCLUSIONS: HI improved 1RM strength similarly and was more effective in improving peak power than was traditional LO in older women. Improvements in lower extremity peak power may exert a greater influence on age-associated reductions in physical functioning than other exercise interventions.     

Upper and lower limb muscle power relationships in mobility-limited older adults

BACKGROUND: Lower limb muscle power impairments are modifiable factors underlying mobility limitations in older adults. This study examined relationships between upper and lower limb muscle power and their role in predicting mobility performance among community-dwelling older adults. METHODS: A cross-sectional analysis was conducted. Participants included 37 mobility-limited adults (24 women, 13 men), aged 65 to 93 years. Measures included upper (elbow extension) and lower limb (double leg press) one repetition maximum (1RM), and muscle power at both 40% and 70% one repetition maximum. Physical performance measures included stair climb time, the Short Physical Performance Battery, and 4-meter walk time. Factors commonly mediating the relationship between impairments and physical performance were analyzed as covariates. RESULTS: Participants had a mean age of 76 years, had five chronic medical conditions, and manifested moderate mobility limitations. Although the associations between the upper and lower limbs were strong (p <.001), the magnitude of association was greater for power (r =.88-.89) as compared to strength (r =.69). Multivariate regression analyses revealed consistently strong relationships between limb muscle power and mobility performance measures. Substituting upper for lower limb power within these models did not materially weaken the relationships. CONCLUSION: Muscle power appears to be a more generalized attribute between the upper and lower limbs than is muscle strength, suggesting that mechanisms underlying velocity of movement, as opposed to force production, may be important factors underlying muscle power in elderly persons. Additionally, upper limb muscle power measures may serve as a useful surrogate measure of limb power having implications for clinicians and researchers.     

Heavy resistance training increases muscle size, strength and physical function in elderly male COPD-patients--a pilot study

This study investigated the effects of heavy resistance training in elderly males with chronic obstructive pulmonary disease (COPD). 18 Home-dwelling male patients (age range: 65-80 years), with a mean forced expiratory volume in the first second (FEV1) of 46 +/- 3.4% of predicted value, were recruited. Baseline and post-training assessments included: Cross-sectional area (CSA) of quadriceps assessed by MRI, isometric and isokinetic knee extension strength, isometric trunk strength, leg extension power, normal and maximal gait-speed on a 30 m track, stair climbing time, number of chair stands in 30 s, lung function (FEV1) and self-reported health. Subjects were randomized to a resistance training group (RE, n = 9) or a control group conducting breathing exercises (CON, n = 9). RE performed heavy progressive resistance training twice a week for 12 weeks. 6 RE and 7 CON completed the study. In RE the following improved (P < 0.05): Quadriceps CSA: 4%, isometric knee extension strength: 14%, isokinetic knee extension strength at 60 degrees /s.: 18%, leg extension power: 19%, maximal gait speed: 14%, stair climbing time: 17%, isometric trunk flexion: 5% and self-reported health. In CON no changes were found. In conclusion, 12 weeks of heavy resistance training twice a week resulted in significant improvements in muscle size, knee extension strength, leg extension power, functional performance and self-reported health in elderly male COPD patients.     

Training implications of maximal forces on a computer-controlled and motor-driven leg press by age group, sex, footplate direction, and speed

Strength training that overloads lengthening muscle fibers may result in greater strength gains with less effort and perceived exertion than conventional training modalities. This study evaluates a device capable of this overloading (a motor-driven and computer-controlled leg press) to develop recommendations for future training interventions. Unimpaired younger and older men and women (7/group, total n=28) performed three maximal-effort trials for both directions of footplate motion (IN and OUT) at three speed profiles (knee rotation speeds of 15, 25, and 35°/s) on a motor-driven and computer-controlled leg press. Normalized forces were tested for effects of age group, sex, direction of footplate motion, and knee rotation speed. Peak forces were 57% greater for younger and 20% greater for IN. Trends of greater IN relative to OUT forces (IN overloading) were present in women, but this was due to an inverse correlation between strength and IN overloading that was independent of age group and sex. Leg press strength training on a device that is capable of overloading lengthening muscle fibers is a promising new training method that appears to have the greatest potential benefits for the weakest participants. Training target profiles on the device tested and others similar to it should be set based on participant-specific maximums across the ROM in both IN and OUT directions at a speed in the middle of the range to be trained.     

Power training improves balance in healthy older adults

BACKGROUND: Age-related decline in muscle power may be an early indicator of balance deficits and fall risk, even in nonfrail adults. This study examined the dose-dependent effect of power training on balance performance in healthy older adults. METHODS: One hundred twelve community-dwelling healthy older adults (69 +/- 6 years) were randomized to 8-12 weeks of power training at 20% (LOW), 50% (MED), or 80% (HIGH) of maximal strength, or a nontraining control (CON) group. Participants trained twice weekly (five exercises; three sets of eight rapid concentric/slow eccentric repetitions) using pneumatic resistance machines. Balance, muscle performance (strength, power, endurance, contraction velocity), and body composition were measured. RESULTS: Power training significantly improved balance performance (p =.006) in participants who underwent power training compared to controls. Low intensity power training produced the greatest improvement in balance performance (p =.048). Average contraction velocity at low load (40% one repetition maximum [1RM]) at baseline independently predicted improvement in balance following training (r = -.29, p =.004). CONCLUSIONS: Power training improves balance, particularly using a low load, high velocity regimen, in older adults with initial lower muscle power and slower contraction. Further studies are warranted to define the mechanisms underlying this adaptation, as well as the optimum power training intensity for a range of physiological and clinical outcomes in older adults with varying levels of health status and functional independence.     

Whole-body-vibration training increases knee-extension strength and speed of movement in older women

OBJECTIVES: To investigate the effects of 24 weeks of whole-body-vibration (WBV) training on knee-extension strength and speed of movement and on counter-movement jump performance in older women. DESIGN: A randomized, controlled trial. SETTING: Exercise Physiology and Biomechanics Laboratory, Leuven, Belgium. PARTICIPANTS: Eighty-nine postmenopausal women, off hormone replacement therapy, aged 58 to 74, were randomly assigned to a WBV group (n=30), a resistance-training group (RES, n=30), or a control group (n=29). INTERVENTION: The WBV group and the RES group trained three times a week for 24 weeks. The WBV group performed unloaded static and dynamic knee-extensor exercises on a vibration platform, which provokes reflexive muscle activity. The RES group trained knee-extensors by performing dynamic leg-press and leg-extension exercises increasing from low (20 repetitions maximum (RM)) to high (8RM) resistance. The control group did not participate in any training. MEASUREMENTS: Pre-, mid- (12 weeks), and post- (24 weeks) isometric strength and dynamic strength of knee extensors were measured using a motor-driven dynamometer. Speed of movement of knee extension was assessed using an external resistance equivalent to 1%, 20%, 40%, and 60% of isometric maximum. Counter-movement jump performance was determined using a contact mat. RESULTS: Isometric and dynamic knee extensor strength increased significantly (P<.001) in the WBV group (mean+/-standard error 15.0+/-2.1% and 16.1+/-3.1%, respectively) and the RES group (18.4+/-2.8% and 13.9+/-2.7%, respectively) after 24 weeks of training, with the training effects not significantly different between the groups (P=.558). Speed of movement of knee extension significantly increased at low resistance (1% or 20% of isometric maximum) in the WBV group only (7.4+/-1.8% and 6.3+/-2.0%, respectively) after 24 weeks of training, with no significant differences in training effect between the WBV and the RES groups (P=.391; P=.142). Counter-movement jump height enhanced significantly (P<.001) in the WBV group (19.4+/-2.8%) and the RES group (12.9+/-2.9%) after 24 weeks of training. Most of the gain in knee-extension strength and speed of movement and in counter-movement jump performance had been realized after 12 weeks of training. CONCLUSION: WBV is a suitable training method and is as efficient as conventional RES training to improve knee-extension strength and speed of movement and counter-movement jump performance in older women. As previously shown in young women, it is suggested that the strength gain in older women is mainly due to the vibration stimulus and not only to the unloaded exercises performed on the WBV platform.     

Six-week improvements in muscle mass and strength during androgen therapy in older men

BACKGROUND: The purpose of our study was to assess the early effects of a potent anabolic androgen on muscle mass and strength, lower extremity power, and functional performance in older men. METHODS: Thirty-two men 72 +/- 6 years of age were randomized to receive oxandrolone (10 mg twice daily) or matching placebo in a 2:1 manner for 12 weeks. Total and appendicular lean body mass (LBM) were assessed by dual-energy x-ray absorptiometry (DEXA). Lower extremity muscle volume was determined by magnetic resonance imaging to validate DEXA changes. RESULTS: Total LBM increased by 2.7 +/- 1.6 kg after 6 weeks with oxandrolone (p <.001), which was greater (p <.001) than the decline in LBM (-0.5 +/- 0.9 kg) with placebo. Appendicular LBM increased by 1.2 +/- 0.9 kg after just 6 weeks with oxandrolone (p <.001), which was greater (p <.001) than the decline in LBM (-0.4 +/- 0.5 kg) with placebo. These changes were >90% of the gains in total and appendicular LBM (3.0 +/- 1.5 kg and 1.3 +/- 0.9 kg, respectively) after 12 weeks. Total thigh and hamstring muscle volume increased by 111 +/- 29 mm(3) (p =.001) and 75 +/- 18 mm(3) (p =.001), respectively, after 12 weeks. Maximal strength increased for the leg press 6.3 +/- 5.6% (p =.003), leg curl 6.7 +/- 8.6% (p =.01), chest press 6.9 +/- 6.5% (p =.001), and latissimus pull-down 4.8 +/- 6.3% (p =.009) with oxandrolone after 6 weeks; these increases were different than those with placebo (p <.001) and were 93%, 96%, 74%, and 94% of the respective gains at week 12. There were no improvements in functional measures. CONCLUSION: Treatment with a potent anabolic androgen may produce significant increases in muscle mass and strength after only 6 weeks in healthy older men. However, such treatment did not improve leg muscle power or walking speed.     

Impairments of muscles and nerves associated with peripheral arterial disease and their relationship with lower extremity functioning: the InCHIANTI Study

OBJECTIVES: To define the relationships between lower extremity peripheral arterial disease (PAD), pathophysiological findings in lower extremity muscles and nerves, and lower extremity performance. DESIGN: Cross-sectional. SETTING: Two communities in Italy. PARTICIPANTS: Nine-hundred seventy-nine community-dwelling men and women aged 60 and older (109 with PAD). MEASUREMENTS: Presence and degree of lower extremity arterial obstruction were determined using the ankle-brachial index (ABI). Lower extremity muscle cross-sectional area was measured using computed tomography. Peroneal nerve conduction velocity (NCV) and leg power were also determined. Measures of lower extremity functioning were fast walking speed over 4 meters, time required to walk 400 meters, and the summary performance score. RESULTS: Participants with PAD had significantly poorer performance on functional outcomes than participants without PAD. Adjusting for age and sex, presence of PAD was associated with reduced leg muscle power (83.69 vs 103.51 watts, P<.001), reduced muscle cross-sectional area (61.5 vs 63.5 cm2, P=.14), and reduced NCV (43.0 vs 44.2 m/s, P=.003). Adjustment for leg power diminished the independent association between ABI and the functional outcomes measures. CONCLUSION: In community-dwelling individuals, PAD is associated with reduced NCV and reduced muscle power in the lower extremities. Muscle power may mediate the association between lower ABI levels and poorer functional performance.     

Lower muscle strength gains in older men with type 2 diabetes after resistance training

This investigation compared the effects of a twice-weekly whole-body supervised progressive resistance training program in older men with type 2 diabetes with those in healthy older men. Twenty sedentary older men participated in a 16-week progressive resistance training study. They were assigned either to a control group (n=11) or to a type 2 diabetes group (n=9). Lower as well as upper body maximal strength (one repetition maximum) and power testing and blood draws to determine basal hormone concentrations (total as well as free testosterone and cortisol) were conducted 4 weeks before training and then at Weeks 0 and 16. The training program consisted of intensities ranging from 50% to 80% of one repetition maximum, 5 to 15 repetitions per set, and three to four sets of each exercise. Baseline maximal muscle strength was not significantly different between groups. After training, significant differences were observed in the magnitude of increments in maximal arm strength and leg strength between the control and type 2 diabetes groups (36.7%+/-12.9% vs. 24.2%+/-4.1%, P=.04, and 35.6%+/-12.2% vs. 17.0%+/-3.8%, P<.01, respectively), whereas no significant difference was observed between groups in the power output increments of the arm and leg extensor muscles (22.5%+/-21.3% vs. 23.8%+/-18.3% and 34.2%+/-32.0% vs. 33.0%+/-21.2%, respectively). At baseline, significant differences were observed in the concentrations of total testosterone and cortisol between the control subjects and the patients with type 2 diabetes (20.3+/-6.0 vs. 10.6+/-2.9 nmol/l, P<.001, and 546.5+/-114.7 vs. 343.2+/-98.4 nmol/l, P<.001, respectively). However, no systematic change was observed during the 16-week strength training period in the basal concentrations of serum total as well as free testosterone and cortisol in both groups. In contrast, statistically significant correlations were observed in a combined group of healthy older men and older men with type 2 diabetes (H+D group) between the mean levels of individual serum total testosterone and cortisol (averaged for the entire training period) and the individual changes in maximal leg strength and arm strength (r=0.85-0.51 and 0.63-0.70, respectively, P<.05). In summary, it would appear that older subjects with type 2 diabetes are equally trainable for muscle power output but not for maximal strength as their healthy counterparts.     

Resistance training enhances insulin-mediated glucose disposal with minimal effect on the tumor necrosis factor-alpha system in older hypertensives

The purpose of the present study was to determine if the improvement in insulin sensitivity after resistance training (RT) is associated with a decline in plasma levels of tumor necrosis factor-alpha (TNF-alpha), soluble TNF-alpha receptor 1 (sTNF R1), and soluble TNF receptor 2 (sTNF R2). Eleven older hypertensives (5 men/6 women, 67 +/- 2 years) participated in a 4-month RT program. Following RT there was a significant increase in upper body (P =.029) and lower body strength (P =.001), assessed by the bench press 1-repetition maximum (1RM) and leg press 1RM, respectively. The RT program produced a significant increase in lean body mass (LBM) (P =.029), a trend for a decline in percent body fat (P =.083), and no change in total body mass (P =.958). Insulin-mediated glucose disposal, assessed by the hyperinsulinemic euglycemic clamp procedure, significantly increased following RT (P =.026). Despite the increase in insulin action, plasma levels of TNF-alpha, sTNF R1, and sTNF R2 were not significantly altered by RT (TNF-alpha: P =.118, sTNF R1: P =.184, sTNF R2: P =.168). In conclusion, a 4-month RT program significantly increased insulin-mediated glucose disposal and LBM without a significant reduction in plasma levels of TNF-alpha, sTNF R1, and sTNF R2 in older hypertensive subjects.     

Impact of whole-body vibration training versus fitness training on muscle strength and muscle mass in older men: a 1-year randomized controlled trial

BACKGROUND: This randomized controlled study investigated the effects of 1-year whole-body vibration (WBV) training on isometric and explosive muscle strength and muscle mass in community-dwelling men older than 60 years. METHODS: Muscle characteristics of the WBV group (n = 31, 67.3 +/- 0.7 years) were compared with those of a fitness (FIT) group (n = 30, 67.4 +/- 0.8 years) and a control (CON) group (n = 36, 68.6 +/- 0.9 years). Isometric strength of the knee extensors was measured using an isokinetic dynamometer, explosive muscle strength was assessed using a counter movement jump, and muscle mass of the upper leg was determined by computed tomography. RESULTS: Isometric muscle strength, explosive muscle strength, and muscle mass increased significantly in the WBV group (9.8%, 10.9%, and 3.4%, respectively) and in the FIT group (13.1%, 9.8%, and 3.8%, respectively) with the training effects not significantly different between the groups. No significant changes in any parameter were found in the CON group. CONCLUSION: WBV training is as efficient as a fitness program to increase isometric and explosive knee extension strength and muscle mass of the upper leg in community-dwelling older men. These findings suggest that WBV training has potential to prevent or reverse the age-related loss in skeletal muscle mass, referred to as sarcopenia.     

Changes in power with resistance training in older and younger men and women

BACKGROUND: Muscle power diminishes with increasing age and inactivity. The capacity for older adults to increase muscle power with resistance exercise has not been examined; therefore, we examined the influence of progressive resistance training (PRT) on muscle power output in 17 men and women aged 56-66 years, and compared their responses to 15 men and women aged 21-30 years. METHODS: All subjects performed 12 weeks of PRT at a workload equivalent to 80% of the one repetition maximum (1RM). All training and assessments of 1RM and power were made on Keiser pneumatic resistance machines. Subjects performed five exercises, three sets per exercise, twice weekly. Muscle power was measured (isotonically) at resistances equivalent to 40, 60, and 80% of the 1RM, on the knee extension and arm pull machines. RESULTS: All subjects increased arm pull power similarly at 40 and 60% of 1RM, independent of age or sex. There was not a significant increase in arm pull power at 80% of 1RM. Older and younger subjects also had similar absolute increases in leg extensor power at 40 and 60% of 1RM, but men responded with greater absolute gains than women at these percentages (p < .05). The increase in leg extensor power at 80% of 1RM was similar in all groups. Older and younger subjects increased strength similarly in all exercises except the left knee extension. Independent of age, men increased strength more than women in all exercises except the double leg press. CONCLUSIONS: These data demonstrate that individuals in their sixth decade can still improve muscle power (and strength); however, men may realize greater absolute gains than women.     

Functional-task exercise versus resistance strength exercise to improve daily function in older women: a randomized, controlled trial

OBJECTIVES: To determine whether a functional-task exercise program and a resistance exercise program have different effects on the ability of community-living older people to perform daily tasks. DESIGN: A randomized, controlled, single-blind trial. SETTING: Community leisure center in Utrecht, the Netherlands. PARTICIPANTS: Ninety-eight healthy women aged 70 and older were randomly assigned to the functional-task exercise program (function group, n=33), a resistance exercise program (resistance group, n=34), or a control group (n=31). Participants attended exercise classes three times a week for 12 weeks. MEASUREMENTS: Functional task performance (Assessment of Daily Activity Performance (ADAP)), isometric knee extensor strength (IKES), handgrip strength, isometric elbow flexor strength (IEFS), and leg extension power were measured at baseline, at the end of training (at 3 months), and 6 months after the end of training (at 9 months). RESULTS: The ADAP total score of the function group (mean change 6.8, 95% confidence interval (CI)=5.2-8.4) increased significantly more than that of the resistance group (3.2, 95% CI=1.3-5.0; P=.007) or the control group (0.3, 95% CI=-1.3-1.9; P<.001). Moreover, the ADAP total score of the resistance group did not change significantly compared with that of the control group. In contrast, IKES and IEFS increased significantly in the resistance group (12.5%, 95% CI=3.8-21.3 and 8.6%, 95% CI=3.1-14.1, respectively) compared with the function group (-2.1%, 95% CI=-5.4-1.3; P=.003 and 0.3%, 95% CI=-3.6-4.2; P=.03, respectively) and the control group (-2.7%, 95% CI=-8.6-3.2, P=.003 and 0.6%, 95% CI=-3.4-4.6; P=.04, respectively). Six months after the end of training, the increase in ADAP scores was sustained in the function group (P=.002). CONCLUSION: Functional-task exercises are more effective than resistance exercises at improving functional task performance in healthy elderly women and may have an important role in helping them maintain an independent lifestyle.     

Assessment of lower extremity muscle power in functionally-limited elders

BACKGROUND AND AIMS: The purpose of this study was to assess the reliability and concurrent validity of a new methodology to evaluate lower extremity muscle power in older, functionally limited men and women. METHODS: A cross sectional evaluation was performed on 58 older men (n=27) and women (n=31) (74.2+/-0.9 years). Knee and hip (leg press) and knee extensor power were evaluated on pneumatic and isokinetic resistance equipment. Incremental single attempt power (IP) testing utilized a single attempt at attaining maximum power at each of six external resistances and was compared to multiple attempt pneumatic power (MP) testing determined by the highest of 5 attempts at achieving maximum power at two set resistances and also with power determined by isokinetic dynamometry. RESULTS: Leg press extension MP yielded significantly greater power than IP at both low (mean=225.3+/-11.85 and 183.9+/-11.52 watts respectively, p<0.001) and high (mean=249.7+/-15.25 and 201.7+/-13.18 watts respectively, p<0.001) external resistances. Knee extension MP also produced significantly greater power when compared to IP at low (mean=82.4+/-4.45 and 69.7+/-4.28 watts respectively, p<0.001) and high (mean=93.7+/-6.3 and 83.2+/-5.93 watts respectively, p<0.001) external resistances. MP testing exhibited excellent reliability at both low (leg press extension: Intra Class Correlation (ICC)=0.93, knee extension: ICC=0.87) and high (Leg press extension: ICC=0.85, Knee Extension: ICC=0.91) external resistances. MP knee extension at 70% 1 RM also showed good agreement with average isokinetic power (R2=0.636). CONCLUSIONS: These findings support the reliability and concurrent validity of MP for the evaluation of muscle power in older individuals.     

Effect of strength and power training on physical function in community-dwelling older adults

BACKGROUND: The performance of daily tasks, such as stair climbing or lifting an object, requires both muscle strength and power. Age-associated reductions in strength and power can affect an older adult's ability to complete daily tasks such as stair climbing and lifting a child. METHODS: The purposes of this study were to determine whether power training was more efficacious than strength training for improving whole-body physical function in older adults and to examine the relationship between changes in anaerobic power and muscle strength and changes in physical function. Thirty-nine men and women (mean age +/- SD = 72.5 +/- 6.3 years) with below-average leg extensor power were randomly assigned to control (C, n = 15), strength-training (ST, n = 13) or power-training (PT, n = 11) groups. The ST and PT groups met 3 days per week for 16 weeks; the C group maintained usual activity and attended three lectures during the course of the study. Primary outcome measures included the Continuous Scale Physical Functional Performance test, maximal strength, and anaerobic power. RESULTS: After baseline was controlled for, the Continuous Scale Physical Functional Performance test total score was significantly greater for the PT group than for the ST (p =.033) and C (p =.016) groups. Maximal strength was significantly greater for the ST group than for the C group (p =.015) after the intervention. There was no significant difference between groups for peak anaerobic power. CONCLUSIONS: Power training was more effective than strength training for improving physical function in community-dwelling older adults.     

Taiji training improves knee extensor strength and force control in older adults

The purpose of this study was to examine the effects of Taiji training on knee extensor strength and force control in older individuals. Twenty-six healthy older adults (71.9 +/- 1.8 years) participated in the study. Sixteen of the older adults (70.2 +/- 1.8 years) underwent Taiji training for 20 weeks (experimental group), whereas the other 10 (74.6 +/- 1.2 years) served as the control group. For both groups, strength and force control of the knee extensors was assessed twice with an isokinetic dynamometer. Strength was assessed with a maximum voluntary isometric contraction (MVC). Force control was measured as the standard deviation (SD) and coefficient of variation (CV) of force during a constant isometric knee extension task at 2%, 30%, 60%, and 90% MVC. For the experimental group, MVC significantly increased (19.5 +/- 4.9%) and the CV of force decreased (18.9 +/- 3.3%) following Taiji training. Improvements in the CV of force were primarily due to decreases in the SD of force (R(2) =.86) rather than increases in strength (R(2) =.12). Furthermore, decreases in SD of force were independent of improvements in strength. For the control group, strength, SD, and CV of force were not different for the 2 tests. The overall findings suggest that Taiji training improves knee extensor strength and force control in older adults.     

Weighted stair climbing in mobility-limited older people: a pilot study

OBJECTIVES: To evaluate weighted stair climbing exercise (SCE) as a means of increasing lower extremity muscle power in mobility-limited older people. DESIGN: Single-blinded, randomized controlled pilot study. SETTING: Human physiology laboratory of a metropolitan university. PARTICIPANTS: Forty-five community-dwelling people aged 65 and older who had baseline mobility limitations manifested by scores of 11 or lower on the Short Physical Performance Battery (SPPB). INTERVENTIONS: Subjects were randomized into one of two 12-week exercise programs. The intervention group (SCE) (n = 23) ascended and descended stairs, at a set pace, while wearing a weighted vest. The control group (WALK) (n = 22) participated in a standardized walking program. MEASUREMENTS: Primary and secondary outcomes included measures of muscle power and strength, submaximal aerobic capacity, and physical performance. RESULTS: SCE produced 17% improvement in double leg press peak power in comparison with WALK (P =.013) and significant improvement in stair climbing power from baseline (12%). Improvement in submaximal aerobic performance was equivalent for both groups. Although not statistically significant, effect size estimates suggest that SCE can potentially influence knee extension power and strength. Stair climb time was improved in both groups, whereas SCE produced significant improvements from baseline SPPB score in a subcohort of participants. CONCLUSIONS: These findings suggest that SCE maybe a useful component of a home exercise program designed to enhance lower extremity muscle power, aerobic capacity, and functional performance. Further investigation is needed involving larger sample sizes and direct comparisons with other forms of resistance training.