The Association Between Incidental Physical Activity and Cardiorespiratory Fitness
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Objective The primary objective of this study was two-fold. First, to determine whether incidental physical activity (IPA), which is composed of both light-intensity physical activity (LPA) and sporadic moderate-intensity physical activity (MPA; physical activity accrued in bouts less than 10 minutes), was associated with cardiorespiratory fitness (CRF). Second, to determine whether sporadic MPA was associated with CRF. Methods Participants were abdominally obese (defined as a waist circumference > 102 cm in men and > 88 cm in women), inactive, adult men (N = 24; [mean ± SD] age = 55.5 ± 7.8 years) and women (N = 55; age = 52.3 ± 7.5 years) recruited from Kingston, Canada. Cardiorespiratory fitness was assessed using a graded treadmill test. IPA (activity ≥ 1 metabolic equivalent (MET)) and sporadic MPA (activity ≥ 3 METs accrued in bouts less than 10 minutes) was measured using the SenseWear Pro Armband (SWA). IPA and sporadic MPA were categorized into duration (minutes/day) and expenditure (MET-minutes/day). In secondary analyses, we investigated the association between LPA (activity between 1 – 2.99 METs), sedentary behaviour (SED; activity < 1.0 MET) and CRF. Results Participants accumulated an average of 326.6 ± 127 minutes of IPA per day which was composed of 40.7 ± 17.8 minutes of sporadic MPA and 285.9 ± 118.2 minutes of LPA. Both duration and expenditure of IPA were significantly associated with CRF independent of sex, however, after further control for body mass index and age neither association remained significant (p > 0.05). Sporadic MPA was significantly associated with CRF after control for covariates (p ≤ 0.05). Neither LPA nor SED were associated with CRF after control for covariates (p > 0.05). Conclusions IPA was not significantly associated with CRF, however, sporadic MPA was an independent predictor of CRF.