期刊
JOURNAL OF APPLIED PHYSIOLOGY
卷 98, 期 1, 页码 211-220出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00294.2004
关键词
older adults; specific strength; specific power; sit-to-stand task
资金
- NCRR NIH HHS [M01 RR 00032] Funding Source: Medline
- NIA NIH HHS [R01 AG 17896] Funding Source: Medline
- NATIONAL CENTER FOR RESEARCH RESOURCES [M01RR000032] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE ON AGING [R01AG017896] Funding Source: NIH RePORTER
The purposes of this study were to examine age and gender differences in knee extensor strength, power, and fatigue using open- and closed-chain testing procedures. We tested the hypothesis that specific strength (strength/unit muscle mass) would not differ by age, whereas age differences in specific power and fatigue would remain consequent to blunted maximal contractile velocity. Skeletal muscle performance was examined in 28 young (26.9 +/- 0.7 yr) and 24 older (63.6 +/- 0.8 yr) men and women. Assessments included one-repetition maximum strength for knee extension, leg press, and squat; concentric knee extensor peak power, velocity, and fatigability; and sit-to-stand power, fatigability, and relative neural activation ( electromyograph activity during sit-to-stand movement normalized to electromyograph activity during isometric maximum voluntary contraction). Thigh lean mass (TLM; kg) was assessed by dual-energy X-ray absorptiometry. Specific strength (N/kg TLM) and specific power (W/kg TLM) were estimated by dividing absolute values by TLM. Age differences in specific strength were observed for knee extension only ( young, 41.2 +/- 1.0 N/kg TLM; older, 32.4 +/- 1.0 N/kg TLM; P < 0.05). Adjustment for TLM did not negate age differences in knee extension specific power ( 25 - 41% lower in older; P < 0.05) across loads tested. Older adults experienced fatigue across 10 repetitions of knee extension as peak velocity fell by 24% ( P < 0.05). Deficits in concentric power persist after adjustment for TLM as maximum contractile velocity falls markedly with aging. Older adults are less capable of sustaining maximum concentric velocity during repetitive contractions. These findings suggest that velocity impairments are a possible contributor to mobility loss and falls risk among older adults. Interventions for improving contractile velocity should be pursued.
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