| PurposeThe purpose of this study was 1) To investigate the current situation of muscle strength of lower extremities in middle-aged and older citizens, and lead them to pay attention to exercise of muscle strength of lower extremities, and provide theoretical evidence for future studies in exercise of muscle strength of lower extremities in this population; 2) To examine the effects of the loaded leg extension exercise on improvement of muscle strength of lower extremities in middle-aged and older citizens, and recommend a convenient and effective exercise prescription for improvement of muscle strength of lower extremities in middle-aged and older citizens provide experimental evidence for future studies in exercise of muscle strength of lower extremities in this population.MethodsThe subjects in this study were 1) 1,847 community-dweller aged 45 or older living in Shanghai, Nanjing and Wuhu where the population and economic development level are of some difference. 2) 32 community-dweller aged 52 or over living in Beilei community of Nanhu, Nanjing city. A questionnaire was used to investigate the demographic data and exercise situation, and a chair rising test (CRT)was used to examine muscle strength of lower extremities in all subjects. The muscle strength of lower extremities and balance (one leg stance test) were examined before and after a 12-week loaded leg extension exercise program, for the subjects living in Beilei community of Nanhu, Nanjing city.Results1.With increased age, CRS time demonstrated a trend of lengthening wholly both in male and female subjects. In the male subjects, the CRT time was changed from 6.86±1.96 sec in subjects aged 45-49 to 12.07±5.30 sec in subjects aged 80 or over. In female subjects, CRT time was changed from 6.58±1.75 sec in subjects aged 45-49 to 9.59±16.62 sec in subjects aged 80 or over. Both of males and females showed obvious downward trends in CRS time after 65 years old. 2. Except of subjects aged 50-54, there were no significant differences in CRT time between the subjects with exercise habit and the subjects without exercise habit. In the three cities, the major exercises of the subjects were walking (37.68%), gymnastics (14.58%) and runing (12.59%). The total amount of the three was 64.85%, while exercise related to the research, whose percentage isonly 0.69% was strength exercise.3.CRT time had a negative correlation to grip strength (r=-0.173,P<0.01), and no significantcorrelation to height, weight and body mass index.4.After the 12 weeks' loaded leg extension exercise, the subjects showed a significant shorter CRTtime and a one leg stance time when compared with before the exercise program (P<0.01, P<0.05).Although the subjects in the control group also showed a significant shorter CRT time in the sameperiod, the change of CRT time before and after the exercise was significant greater in exercisegroup when compared with the controls(P<0.05).5.The improving degree of chair stand time has no relation with the total amount of load and totaltime of exercise, but it has close relation to the basic level (P<0.001); the improving degree of oneleg stance time has close relation to the total amount of exercise load and total time of exercise(P<0.05),but it has on relation with the basic level.Conclusions1. Muscle strength of lower extremities declined with age in middle-aged and older citizens, and itdemonstrated a greater decline after 65 years.2.The exercises that the most middle-aged and older citizens participated in had no effect to theirmuscle strength of lower extremities.3.Loaded leg extension exercise is a simple and effective training way to muscle strength of lowerextremities. It can effectively improve their muscle strength of lower extremities and the balance.4.The more time of CRT before exercise, the more improvement they could get through exercise.The larger of total amount of exercise loading is and the more the time of total exercise is, themore improvement of the one leg stance could get. |
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