Is Intermittent Moderate Intensity Physical Activity Associated with Cardiorespiratory Fitness?

Abstract

Background: It is well established that moderate intensity physical activity performed in 10-minute bouts is positively associated with cardiorespiratory fitness (CRF). Whether moderate intensity physical activity performed intermittently (IMPA) during normal activities of daily living is associated with CRF is unclear. Purpose: To determine whether objectively measured IMPA is associated with CRF in adults. Methods: Participants included 289 (75% female) adults with overweight or obesity (BMI 32.7± 5.0 kg/m2 (mean±SD)) initially recruited to participate in one of two exercise studies. Physical activity variables were obtained using a hip-worn accelerometer. Bouted moderate to vigorous intensity physical activity (MVPA) was defined as ≥ 10 consecutive minutes. IMPA was defined as any MPA minute outside of bouted MVPA. Light intensity physical activity (LPA) was defined as activity between 101-1951cpm with no bouting requirement. CRF was assessed during a maximal graded treadmill test using indirect calorimetry. Results: Participants accumulated 14±9 minutes/day of IMPA. The average intensity of IMPA minutes was 3.5±0.2 METs. IMPA was positively associated with CRF after control for age, biological sex, bouted MVPA, and LPA (partial r = 0.09, p=0.05). IMPA intensity was a significant predictor of CRF independent of covariates and IMPA minutes (p<0.05). LPA was associated with CRF after control for age, biological sex and IMPA (r=0.14, p<0.05). The combination of LPA and IMPA was significantly associated with CRF independent of age and biological sex (partial r=0.20, p<0.001). Conclusion: IMPA minutes were modestly associated with CRF independent of age, biological sex, and other PA variables. The combination of IMPA and LPA explained a greater variance in CRF than either behaviour alone.