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Intensity of Physical Activity as a Determinant of Leg Strength and Power in Physically Independent Elderly People

Yutaka Yoshitake, Department for Interdisciplinary Studies of Lifelong Sport and Physical activity, National Institute of Fitness and Sports; Akiyo Tsuneyoshi, Hiroshi Nagayama, Akira Maeda, Kozi Zushi, Department for Interdisciplinary Studies of Lifelong Sport and Physical Activity, National Institute of Fitness and Sports, Japan; Sawako Wakui, Hokkaido University of Education Iwamizawa Campus, 2-34 Midorigaoka, Iwamizawa, Hokkaido, 068-8642 Japan; Misaki Sumino, Department for Interdisciplinary Studies of Lifelong Sport and Physical Activity, National Institute of Fitness and Sports, Japan; Mieko Shimada, Chiba College of Health Science, 2-10-1 Wakaba, Mihama-ku, Chiba, Chiba, 261-0014 Japan; Kazuto Saito, Takafumi Hamaoka, Naotake Inoue, Department for Interdisciplinary Studies of Lifelong Sport and Physical Activity, National Institute of Fitness and Sports, Japan


Background: The beneficial effects of walking on cardio-respiratory fitness, mortality, and mobility in older adults are well established. Although previous investigations have examined the relationship between daily steps and leg strength and power, no consistent results were obtained for elderly adults living independently in the community. The purposes of the current study were to examine the relationships among daily walk steps, the intensity of physical activity, walking speed, leg strength, and power in elderly people living independently.

Methods: Fifty-eight women (age: 73 ± 5 years) and 57 men (age: 76 ± 6 years) were recruited from the community. The daily steps, and the intensity and time of PA were measured using a single-axis accelerometer. The accelerometer was attached to a belt or waistband of the subject’s clothing during waking hours over a 1-2-week period. Maximal isometric knee extensor strength was determined by a portable chair incorporating a strain gauge connected to a load cell. The subjects sat on a seat in a vertical position that was adjusted comfortably with their legs hanging vertically and knees bent at 90°. Maximal leg extensor power was measured with an isokinetic leg power system in a sitting position. Each subject was instructed to sit down on the instrument and press his or her feet forward on the plate as fast as possible with their legs fully extended. Maximum handgrip strength was measured using a Smedley hand dynamometer. Maximal stepping rate for 10 s was used as an index of agility using an industrial stepping rate counter. The subjects stepped alternately as fast as possible with each leg while in a sitting position for 10 s. To measure maximum walking speed, the subjects walked on a straight walkway 10 m in length on a flat floor twice at their maximum speed. One-leg standing time with eyes open was measured with eyes open and arms out, standing on one foot with the other off the floor.

Results: The average steps per day were significantly correlated with the walking speed and leg extension strength in women, but not in men. The time spent in moderate-intensity PA was significantly correlated with leg extensor strength, leg extensor power and maximum walking speed in women, on the other hand the time spent in high-intensity PA was significantly correlated with leg extension strength, leg extensor power, and maximum walking speed in men. In a multiple regression analysis, for leg strength or leg power, a higher coefficient value was obtained for the time in moderate- and high-PA than for the average steps per day. The coefficients of the time spent in moderate- and high-PA were statistically significant but not the time spent in low-intensity PA.

Conclusions: The level of leg extension strength and power in physically independent elderly people is attributable to the time spent in moderate- and high-intensity PA.





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