Adiposity and age explain most of the association between physical activity and fitness in physically active men

Background

To determine if there is an association between physical activity assessed by the short version of the International Physical Activity Questionnaire (IPAQ) and cardiorespiratory and muscular fitness.

Methodology/Principal Findings

One hundred and eighty-two young males (age range: 20–55 years) completed the short form of the IPAQ to assess physical activity. Body composition (dual-energy X-Ray absorptiometry), muscular fitness (static and dynamic muscle force and power, vertical jump height, running speed 30 m sprint], anaerobic capacity 300 m running test]) and cardiorespiratory fitness (estimated VO₂max: 20 m shuttle run test) were also determined in all subjects.Activity-related energy expenditure of moderate and vigorous intensity (EEPA_moderate and EEPA_vigorous, respectively) was inversely associated with indices of adiposity (r?=??0.21 to ?0.37, P<0.05). Cardiorespiratory fitness (VO₂max) was positively associated with LogEEPA_moderate (r?=?0.26, P<0.05) and LogEEPA_vigorous (r?=?0.27). However, no association between VO₂max with LogEEPA_moderate, LogEPPA_vigorous and LogEEPA_total was observed after adjusting for the percentage of body fat. Multiple stepwise regression analysis to predict VO₂max from LogEEPA_walking, LogEEPA_moderate, LogEEPA_vigorous, LogEEPA_total, age and percentage of body fat (%fat) showed that the %fat alone explained 62% of the variance in VO₂max and that the age added another 10%, while the other variables did not add predictive value to the model VO₂max ?=?129.6?(25.1× Log %fat) ? (34.0× Log age); SEE: 4.3 ml.kg^?1. min^?1; R²?=?0.72 (P<0.05)]. No positive association between muscular fitness-related variables and physical activity was observed, even after adjusting for body fat or body fat and age.

Conclusions/Significance

Adiposity and age are the strongest predictors of VO₂max in healthy men. The energy expended in moderate and vigorous physical activities is inversely associated with adiposity. Muscular fitness does not appear to be associated with physical activity as assessed by the IPAQ.