Association Between Physical Activity And Oxygen Consumption During Maximal And Submaximal Exercise In Middle- And Older-aged Adults

Introduction: Although physical activity (PA) is considered an important determinant of exercise capacity (EC), the association between PA and EC is usually modest. Previous research has demonstrated an important contribution of age on determination of EC, with a rate of decline in maximal oxygen consumption that accelerates with each successive age decade, regardless of PA levels. Moreover, daily PA levels may contribute more to submaximal EC than maximal EC, but no previous study has tested this hypothesis. Methods: We investigated the associations between self-reported and objectively-measured PA and maximal and submaximal EC in 413 (?.40 years old) participants the Baltimore Longitudinal Study of Aging. Participants underwent maximal and submaximal EC evaluations, completed a PA questionnaire, and provided chest-worn uniaxial accelerometer data for a minimum of 3 up to 7 days. Maximal and submaximal EC were assessed as VO2 (ml/kg/min) reached during a treadmill-based maximal cardiopulmonary exercise test (CPET) and the Long-Distance Corridor Walk Test (LDCW), respectively. The partial coefficient of determination from each PA variable was used to assess the percentage of variance in EC explained by each PA variable. The interaction between sex and age was also evaluated to examine whether age had a differential association within sex. Results: Overall, accelerometer-based PA variables better explained the EC variation than self-reported PA variables. Vigorous PA (22% in women and 16% in men) and total volume of daily PA (17% in women and 13% in men) measured by accelerometer explained the most variability in maximal EC. The variance in submaximal EC was only moderately explained by the PA variables (all <11%). Age explained more of the variance in EC among men than women (32% vs 19%; p-value for age by sex interaction =0.02). Moreover, age contributed more to the variance in maximal EC than any PA variable in men (32% for age vs 16% for vigorous PA from accelerometer), while vigorous PA from the accelerometer better explained variance in maximal EC among women (19% for age vs 22% for vigorous PA from accelerometer). Conclusion: Accelerometer-derived vigorous and total volume of daily PA contributes to the determination of maximal EC in mid-to-late life. PA contributed more to maximal EC determination in women than in men. The importance of age in determining EC reinforces the necessity of strategies to attenuate declines in EC with aging. 

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