Comparing self-reported physical activity and sedentary time to objective fitness measures in a military cohort

Objectives Regular vigorous physical activity (PA) and high levels of physical fitness (PF) confer health benefits. Conversely, sedentary time is a risk factor for chronic illness, independent of PA. We evaluated associations between self-reported PA, sedentary time, and objective PF measures in military Service members. Design Cross-sectional study including 10,105 Air Force Millennium Cohort participants with a valid physical fitness assessment (PFA). Methods Linear regression assessed associations between self-report PA, screen time, and usual activity and abdominal circumference (AC) and VO2 max; logistic regression was used for PFA failure. We stratified by age and sex. Results Men who self-reported high versus low levels of PA had greater AC (19–29 years: β = 0.23 in., 95% CI 0.07, 0.39; 30–39 years: β = 0.45 in., 95% CI 0.17, 0.72). High versus low self-reported PA was also associated with greater VO2Max (β =: 0.81–1.41 mL/kg/min). Self-reported strength training for ≥2 days/week was associated with greater VO2Max in 19–29 year old men (β = 0.84 mL/kg/min, 95% CI 0.09, 0.60) and 30–39 year old women (β = 0.74 mL/kg/min, 95% CI 0.02, 1.46). For younger men and women, Conclusions Self-reported PA and screen time were associated with some objective PF measures, including VO2Max and AC. However, screen time alone was associated with PFA failure.