Metter E Jeffrey, Talbot Laura A, Schrager Matthew, Conwit Robin A
Clinical Research Branch, National Institute on Aging, NIA-ASTRA, Harbor Hospital, Baltimore, Maryland 21225, USA.
J Appl Physiol (1985). 2004 Feb;96(2):814-21. doi: 10.1152/japplphysiol.00370.2003. Epub 2003 Oct 10.
Poor muscle strength is associated with mortality, presumably due to low muscle mass. Notably, muscle power declines more rapidly than muscle strength with increasing age, which may be related to more complex central nervous system movement control. We examined arm-cranking power against four workloads and isometric strength measured in the upper extremities of 993 men longitudinally tested over a 25-yr period. Muscle mass was estimated by using 24-h creatinine excretion; physical activity was assessed by self-reported questionnaire. Muscle power and strength were modeled by time by using mixed-effects models, which developed regression equations for each individual. The first derivative of these equations estimated rate of change in strength or power at each evaluation. Survival analyses, using the counting method, examined the impact of strength, power, and their rates of change on all-cause mortality while adjusting for age. Arm-cranking power [relative risk (rr) = 0.984 per 100 kg.m.min(-1), P < 0.001] was a stronger predictor of mortality than was arm strength (rr = 0.986 per 10 kg, P = not significant), whereas rate of power change (rr = 0.989 per 100 kg.min(-1).yr(-1)) and rate of arm strength change (rr = 0.888 per 10 kg/yr) were risks independent of the power or strength levels. The impacts of power and strength were partially independent of muscle mass and physical activity. The risk of mortality was similar across the four power workloads (rr = 0.93-0.96 per 100 kg.m.min(-1)), whereas the lowest load generated less than one-half the power as the higher loads. Arm-cranking power is a risk factor for mortality, independent of muscle strength, physical activity, and muscle mass. The impact is found with loads that do not generate maximal power, suggesting an important role for motor coordination and speed of movement.
肌肉力量差与死亡率相关，可能是由于肌肉量低。值得注意的是，随着年龄增长，肌肉功率比肌肉力量下降得更快，这可能与更复杂的中枢神经系统运动控制有关。我们在993名男性的上肢中，针对四种工作量测试了手摇曲柄功率，并测量了等长力量，这些男性在25年期间接受了纵向测试。通过24小时肌酐排泄量估算肌肉量；通过自我报告问卷评估身体活动。使用混合效应模型按时间对肌肉功率和力量进行建模，为每个个体建立回归方程。这些方程的一阶导数估计每次评估时力量或功率的变化率。使用计数法进行生存分析，在调整年龄的同时，研究力量、功率及其变化率对全因死亡率的影响。手摇曲柄功率（相对风险[r r]=每100 kg·m·min⁻¹为0.984，P<0.001）比手臂力量（r r=每10 kg为0.986，P无显著性）更能预测死亡率，而功率变化率（r r=每100 kg·min⁻¹·年⁻¹为0.989）和手臂力量变化率（r r=每10 kg/年为0.888）是独立于功率或力量水平的风险因素。功率和力量的影响部分独立于肌肉量和身体活动。在四种功率工作量下，死亡率风险相似（r r=每100 kg·m·min⁻¹为0.93 - 0.96），而最低负荷产生的功率不到较高负荷的一半。手摇曲柄功率是死亡率的一个风险因素，独立于肌肉力量、身体活动和肌肉量。在未产生最大功率的负荷下也发现了这种影响，表明运动协调和运动速度起重要作用。
