Laboratory of Epidemiology, Demography, and Biometry, National Institute on Aging, 7201 Wisconsin Ave, 3C309, Bethesda, MD 20892, USA.
J Am Geriatr Soc. 2010 Feb;58(2):219-26. doi: 10.1111/j.1532-5415.2009.02681.x.
To examine the association between physical fitness, assessed according to ability and time to complete a 400-m walk, on changes in body composition and muscle strength over a 7-year period.
Prospective observational cohort study.
Memphis, Tennessee, and Pittsburgh, Pennsylvania.
Two thousand nine hundred forty-nine black and white men and women aged 70 to 79 participating in the Health, Aging and Body Composition Study.
Body composition (fat and bone-free lean mass) was assessed using dual-energy X-ray absorptiometry in Years 1 to 6 and 8. Knee extension strength was measured using isokinetic dynamometry and grip strength using isometric dynamometry in Years 1, 2, 4, 6, and 8.
Less fit people weighed more and had a higher total percentage of fat and a lower total percentage of lean mass than very fit men and women at baseline (P<.001). Additionally, the least fit lost significantly more weight, fat mass, and lean mass over time than the very fit (all P<.01). Very fit people had the highest grip strength and knee extensor strength at baseline and follow-up; decline in muscle strength was similar in every fitness group.
Low fitness in old age was associated with greater weight loss and loss of lean mass than with high fitness. Despite having lower muscle strength, the rate of decline in the least fit persons was similar to that in the most fit. In clinical practice, a long-distance walk test as a measure of fitness might be useful to identify people at risk for these adverse health outcomes.
根据完成 400 米步行的能力和时间评估体能，并研究其与 7 年内身体成分和肌肉力量变化的关系。
前瞻性观察队列研究。
田纳西州孟菲斯和宾夕法尼亚州匹兹堡。
2949 名年龄在 70 至 79 岁的黑人和白人男性和女性，参加了健康、衰老和身体成分研究。
在第 1 年至第 6 年和第 8 年使用双能 X 射线吸收法评估身体成分（脂肪和无骨瘦体重）。在第 1 年、第 2 年、第 4 年、第 6 年和第 8 年使用等速测力法测量膝关节伸展力量，使用等长测力法测量握力。
体能较差的人在基线时体重更重，总脂肪百分比和瘦体重百分比均高于体能非常好的男性和女性（P<.001）。此外，体能最差的人在整个随访期间体重、体脂肪和瘦体重的减少量显著高于体能非常好的人（均 P<.01）。体能非常好的人在基线和随访时握力和膝关节伸肌力量最高；在每个体能组中，肌肉力量的下降速度相似。
与高体能相比，老年时体能较低与体重减轻和瘦体重减少有关。尽管肌肉力量较低，但体能最差者的下降速度与体能最好者相似。在临床实践中，长距离步行测试作为一种体能评估可能有助于识别有这些不良健康结果风险的人群。
