Incidental physical activity is positively associated with cardiorespiratory fitness

The primary aim was to determine whether incidental physical activity (IPA), expressed either as duration or intensity, was associated with cardiorespiratory fitness (CRF).

Participants were inactive abdominally obese men (n = 43, waist circumference ≥ 102 cm) and women (n = 92, waist circumference ≥ 88 cm) recruited from Kingston, Canada. IPA (>100 counts per minute) was determined by accelerometry during 7 d and categorized into duration (min·d(-1)) and intensity (counts per minute). In secondary analyses, IPA was further categorized as light physical activity (LPA, 100-1951 counts per minute) and sporadic moderate physical activity (MPA, ≥ 1952 counts per minute accumulated in bouts <10 consecutive minutes). CRF was assessed using a maximal treadmill exercise test.

Participants accumulated 308.2 ± 98.8 (mean ± SD) min of IPA per day of which 19.2 ± 13.5 min was spent in sporadic MPA. Mean CRF was 26.8 ± 4.7 mL·kg(-1) body weight·min(-1). IPA duration was positively associated with CRF in the univariate model (r2 = 0.03, P < 0.05) and after control for gender and body mass index (r2 = 0.53, P < 0.01). Likewise, IPA intensity was positively associated with CRF in univariate (r2 = 0.18, P < 0.001) and multivariate analyses (r2 = 0.56, P < 0.01). After further control for each other, IPA duration was not associated with CRF (P = 0.05), whereas IPA intensity remained a significant predictor (r2 = 0.57, P < 0.001). In secondary analyses, LPA was not associated with CRF (P > 0.05). Sporadic MPA was associated with CRF (r2 = 0.20, P < 0.001) and remained a positive correlate after control for gender, body mass index, and the other physical activity variables (r2 = 0.60, P < 0.001).

In this study, both duration and intensity of IPA were positively associated with CRF among inactive abdominally obese adults. Sporadic MPA, but not LPA, was an independent predictor of CRF.