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