Longitudinal changes in selected physical capabilities: muscle strength, flexibility and body size.

OBJECTIVES: first, to record, in a representative sample of older men and women, longitudinal changes in (i) maximal voluntary strength of the handgrip muscles, (ii) maximal range of movement in the shoulder joint and (iii) body weight and skeletal size; second, to explore associations between the changes in muscle strength and both customary physical activity and health outcomes.
DESIGN: longitudinal analyses of survivors measured at baseline, and 4-year and 8-year follow-ups. PARTICIPANTS: 350 survivors of a random sample originally aged 65 and over.
RESULTS: over 8 years average loss of body weight was slight but significant at about 2 kg (less than 5%). Loss of shoulder range was negligible, while loss of muscle strength was significant at about 40 N (less than 2% per year). Demispan remained stable across all three points of measurement. These mean values concealed substantial variation in the rate of loss of strength, which was twice as fast in the older groups, especially in the women. These losses could not be attributed to worsening health, although this was observed. All the respondents had at least two chronic health problems at the 8-year stage. For the changes in handgrip strength, reduced reported habitual use of the handgrip muscles and increased symptoms of anxiety and depression were significant independent covariates in addition to age and time (all P < 0.0001).
CONCLUSION: there are significant independent associations between the loss of muscle strength in old age and both decline in physical activity and increase in depression scores. This is strongly suggestive of causal links and confirms the need to encourage physical activity and control depression in order to maintain strength and function in old age.