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.

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.

The relationship between leg power and physical performance in mobility-limited older people.

OBJECTIVES: The purpose of this study was to assess the influence of leg power and leg strength on the physical performance of community-dwelling mobility-limited older people. DESIGN: Cross-sectional analysis of baseline data from a 12-week randomized controlled exercise-intervention study. SETTING: Exercise laboratory within the Department of Health Science of an urban university. PARTICIPANTS: Forty-five community-dwelling mobility-limited people (34 women, 11 men), aged 65 to 83. MEASUREMENTS: Health status, depression, cognition, physical activity, and falls efficacy; physiological measures of lower extremity strength and power; and measures of physical performance. RESULTS: Through bivariate analyses, leg power was significantly associated with physical performance as measured by stair-climb time, chair-stand time, tandem gait, habitual gait, maximal gait, and the short physical performance battery describing between 12% and 45% of the variance (R2). Although leg power and leg strength were greatly correlated (r = .89) in a comparison of bivariate analyses of strength or power with physical performance, leg power modeled up to 8% more of the variance for five of six physical performance measures. Despite limitations in sample size, it appeared that, through quadratic modeling,the influence of leg power on physical performance was curvilinear. Using separate multivariate analyses, partial R2 values for leg power and leg strength were compared, demonstrating that leg power accounted for 2% to 8% more of the variance with all measures of physical performance. CONCLUSION: Leg power is an important factor influencing the physical performance of mobility-limited older people. Although related to strength, it is a separate attribute that may exert a greater influence on physical performance. These findings have important implications for clinicians practicing geriatric rehabilitation.

The expression of neuregulin and erbB receptors in human skeletal muscle: effects of progressive resistance training.

The neuregulin/erbB-signaling axis contributes to the development and growth of multiple mammalian tissues including skeletal muscle. In this study, we sought to characterize the native expression of this system in human skeletal muscle and test the hypothesis that a program of progressive resistance training (PRT) would regulate the expression of neuregulin (NRG) and its cognate receptors. Twelve healthy-male subjects underwent 8-weeks of lower-extremity PRT and muscle biopsies were performed at baseline and following 1- and 8-weeks of the intervention. PRT resulted in significant gains in skeletal muscle strength without appreciable changes in fiber size or myosin heavy chain (MHC) composition. At baseline, Western Blot analysis demonstrated expression of erbB2, erbB3 and erbB4 receptors and multiple NRG isoforms. Following 1- and 8-weeks of PRT, no changes erbB2, erbB4 or NRG expression were observed. ErbB3 expression, however, was significantly increased at both time points compared to baseline. Double labeling of muscle cross-sections revealed increased expression of erbB3 following PRT was not exclusive to fibers staining positive for MHC IIa. Thus, erbB2, erbB3, erbB4 and multiple NRG isoforms are natively expressed in human skeletal muscle. Following PRT, a significant increase in erbB3 was observed. The ability to detect basal expression and alterations in response to physiologic stimuli merit further studies examining the role of this system in skeletal muscle.