Abstract
Introduction: observational studies do not always find positive associations between physical activity and muscle strength despite intervention studies consistently showing that exercise improves strength in older adults. In previous analyses of the MRC National Survey of Health and Development (NSHD), the 1946 British birth cohort, there was no evidence of an association between leisure time physical activity (LTPA) across adulthood and grip strength at age 53. This study tested the hypothesis that cumulative benefits of LTPA across mid-life on grip strength will have emerged by age 60–64.Methods: data from the MRC NSHD were used to investigate the associations between LTPA at ages 36, 43, 53 and 60–64 and grip strength at 60–64. Linear regression models were constructed to examine the effect of activity at each age separately and as a cumulative score, including adjustment for potential confounders and testing of life course hypotheses.Results: there were complete longitudinal data available for 1,645 participants. There was evidence of a cumulative effect of LTPA across mid-life on grip strength at 60–64. Compared with the third of participants who reported the least LTPA participation across the four time points, those in the top third had on average 2.11 kg (95% CI: 0.88, 3.35) stronger grip after adjustments.Conclusions: increased levels of LTPA across mid-life were associated with stronger grip at age 60–64, in both men and women. As these associations have emerged since age 53, it suggests that LTPA across adulthood may prevent decline in grip strength in early old age.
Highlights
Observational studies do not always find positive associations between physical activity and muscle strength
Being more active at age 53 was associated with stronger grip but in men only. These findings attenuated after adjustment for confounders but associations with leisure time physical activity (LTPA) at 53 and 60–64 remained; for example, those who were most active at 60–64 had a mean grip strength 1.73 kg greater than those who were inactive
There was strong evidence of a linear trend between the cumulative LTPA score and grip strength; a one point increase in the score was associated with a 0.39 kg stronger grip, after adjustment for confounders
Summary
Observational studies do not always find positive associations between physical activity and muscle strength. Using data from the Medical Research Council National Survey of Health and Development (MRC NSHD), we found no benefit of increased leisure time physical activity (LTPA) across mid-life on grip strength at age 53 years, despite evidence of cumulative benefits of LTPA on other objective measures of physical capability [1]. This finding was similar to results from other observational studies which have not found consistent evidence of positive associations between physical activity and strength in both men and women [2,3,4]. The aim of this study was to test the hypothesis that cumulative benefits of increased LTPA in mid-life on grip strength will be evident in the NSHD at age 60–64
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