Work

Relative and absolute intensity accelerometer metrics decipher the effects of age, sex, and occupation on physical activity

Year: 2025

Type: article

Abstract: Background To investigate whether quantifying both the absolute and relative intensity of physical activity (PA) improves understanding of age, sex, and occupation-related differences in PA in healthy adults aged 20–89. Methods In the cross-sectional COmPLETE study, participants (N = 460, 48% women, age 55 [IQR 37, 71]) wore accelerometers for up to 14 days and underwent cardiopulmonary exercise testing. Average intensity (AvAcc) and distribution of intensity (IG) of PA across the day were expressed in absolute terms (_ABS) and relative (_REL) to the acceleration at the individual´s maximum intensity, predicted from cardiorespiratory fitness. Results After initial increases, AvAcc_ABS and IG_ABS continuously declined beyond age 40–45, whereas AvAcc_REL and IG_REL increased until stabilising at age ~ 70 and declining at age ~ 60, respectively. Cardiorespiratory fitness constantly declined. Women had trivially higher AvAcc_ABS and moderately higher AvAcc_REL, but not IG_ABS and IG_REL, than men. Occupations involving ≥ moderate PA showed higher AvAcc_ABS and AvAcc_REL, but not IG_ABS and IG_REL indicating longer periods of low-intensity PA, compared to sitting/standing occupations. Conclusions Distinct age trajectories of absolute and relative metrics as well as cardiorespiratory fitness suggest that the age-related decline in the latter preceded that of PA. Women’s higher AvAcc_ABS and AvAcc_REL relate to more low-intensity PA combined with lower cardiorespiratory fitness rather than more health-enhancing higher-intensity PA. Finally, the intensity profile of occupational PA may provide insight into why occupational PA appears to lack a prophylactic association with health. Quantifying both the absolute and relative intensity of accelerometer-assessed PA provides greater insight than either alone. Trial registration: On clinicaltrials.gov (NCT03986892). Retrospectively registered 14 June 2019.

Source: BMC Public Health

DOI: 10.1186/s12889-025-21800-w