Introduction The ability to perform bodily movement varies in ageing men and women. We investigated whether physical fitness may explain sex differences in daily physical activity energy expenditure (PAEE) among older people. Methods A population-based cohort of 75, 80, and 85-year-old men and women (n=409, 62 % women) underwent laboratory-based assessment of walking speed, maximal knee extension strength, and body fat percentage. Free-living physical activity was assessed as total PAEE, and light (LPA) and moderate-to-vigorous physical activity (MVPA) using individually calibrated combined accelerometry and heart rate sensing. Path modelling was used to examine indirect associations between sex, physical fitness, and physical activity. Results Men had a more favourable physical fitness profile and higher overall PAEE (mean 34.0 (SD 10.8) kJ/kg/day) than women (28.3 (8.4) kJ/kg/day, p<0.001). The path model for PAEE explained 33 % of the variance. The direct association of sex on PAEE was non-significant, whereas the association between sex and PAEE through body fat (β=0.20, p<0.001) and walking speed (β=0.05, p=0.001) were statistically significant. Similarly, the associations between sex and MVPA through body fat (β=0.11, p=0.002) and walking speed (β=0.05, p=0.001) were significant, as were the associations between sex and LPA through body fat (β=0.24, p<0.001) and walking speed (β=0.03, p=0.019). Conclusion Differences in physical activity between men and women may reflect underlying differences in cardiorespiratory fitness and adiposity. These results highlight the importance of maintaining physical fitness to support active living in older adults.

The authors have declared no competing interest.

This work was supported by the European Research Council (grant number 693045 to TaR), Yrjö Jahnsson Foundation (to LK), and the Academy of Finland (grant numbers 339391 and 346462 to LK, and 321336, 328818, and 352653 to TiR). KW, TG, and SB were funded by the UK Medical Research Council (MC_UU_00006/4) and the NIHR Cambridge Biomedical Research Centre (NIHR203312 and IS-BRC-1215-20014). The content of this publication does not reflect the official opinion of the funders. Responsibility for the information and views expressed in the publication lies entirely with the authors.

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Ethics committee of Wellbeing Services County of Central Finland (former Central Finland Health Care District) gave ethical approval for this work

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https://doi.org/10.17011/jyx/dataset/83811