Objective: To research the natural changes in maximal isometric strength, over a period of 5 years, in men and women aged 75 at baseline, and to study the effect of everyday physical activity on strength alterations.
Design: A 5-year longitudinal study.
Setting: Exercise laboratory.
Participants: The target group in 1989 was the total 75-year-old population of Jyväskylä. One hundred one men (81%) and 186 women (75%) participated in baseline strength tests, and after 5 years, 55 men and 111 women (70% and 72% of the survivors) took part in the follow-up measurements.
Methods: Maximal isometric hand grip, arm flexion, knee extension, trunk flexion, and trunk extension forces were measured using dynamometers. Self-rated physical activity was recorded using a scale by Grimby (1986). Strength changes were compared between groups based on the amount of everyday physical activity: (1) remained active (AA, 24 men, 24 women); (2) remained sedentary (SS, 11 men, 43 women); (3) decreased activity (AS, 11 women); and (4) increased activity (SA, 32 women). AS and SA could be formed for women only because of the small number of men. All analyses were stratified by gender.
Main results: The average percentage change in strength over 5 years among survivors varied from a 4% increase in knee extension strength observed in men and women to a 16% decrease in grip strength in women. The grip strength decrease was greater in women than men. The AA men maintained their trunk extension strength at a higher level than the SS men. Time by group interactions in men were not significant. In women, the rate of decline in AS was 32% in grip and 27% in elbow flexion strength, which was greater than in the other activity groups. The AA women retained their knee extension strength at a higher level than the other groups. Those who died before follow-up tests exhibited poorer strength test results at baseline. Physical activity decreased over follow-up.
Conclusions: Strength alterations with age differed between muscle groups. Undertaking everyday physical activities such as household work, walking, and gardening, which are also the most common physically demanding activities of older people, may play an important role in maintaining strength at an adequate level for independent living.