Abstract: Objective To explore the effect of different dosage of physical activities on muscle strength, physical fitness and sleep quality of the frail elderly. Methods A total of 88 frail elderly meeting the inclusion criteria were enrolled and randomly divided into control group, small-amount and medium-intensity group, small-amount and high-intensity group, large-amount and high-intensity group, with 22 elderly in each group. The control group did not have any targeted physical training. The three intervention groups practiced resistance exercise of lower limbs with the corresponding amount and intensity of physical exercise according to the scheme. The muscle strength of lower limb, physical fitness and sleep status of the frail elderly were evaluated before and 12 weeks after the intervention. Results There were no significant differences in the muscle strength of lower limb, physical fitness and sleep status before and after the intervention in the control group (P>0.05); Compared with those before intervention, the above indexes in the other three exercise groups were improved significantly after the intervention (P<0.05 or P<0.01). Compared with small-amount and medium-intensity group, the muscle strength of lower limbs, 6-minute walking distance, 30-second sit-to-stand test and total sleep time in small-amount and high-intensity group, large-amount and high-intensity group were significantly improved (P <0.01). Conclusions Resistance exercise can effectively improve the muscle strength, physical fitness and sleep of the frail elderly. The amount and intensity of physical activity are conducive to the improvement of muscle strength, physical fitness and sleep status in the frail elderly, but the intensity of physical activity is the main factor influencing the above health indicators.

Key words: aged, frailty, physical activity, exercise dosage, muscle strength