Comprehensive evaluation of a single-stage submaximal treadmill walking protocol in healthy, middle-aged women

Cardiorespiratory fitness is an independent predictor of cardiovascular events in women; however, maximal oxygen consumption (VO _2max) protocols are not always feasible. The Evaluation of Physical Activity Measures in Middle-Aged Women Study was a 6-week study designed to evaluate six physical activity (PA) measures in women, aged 45-65 years. We investigated the Ebbeling submaximal treadmill (EbbTM) protocol's ability to reflect an active lifestyle in 66 women [median (IQR) age, 51.0 (48.0, 56.5) years]. Participants were screened using ACSM and AHA guidelines and classified as moderate or low cardiovascular risk. VO _2max was estimated using the EbbTM in all participants (TEST1). Moderate risk women repeated the EbbTM (TEST2) while low risk completed a maximal treadmill test. Intraclass correlation coefficients (ICC) and minimal detectable change (MDC ₉₀) score were calculated to examine reliability. Spearman rank order or Pearson product-moment correlation coefficients were used to determine the association between estimated VO _2max and physical fitness and activity measures. Estimated VO _2max from the EbbTM protocol had excellent reproducibility [ICC = 0.95 (95% CI: 0.89, 0.98) and MDC ₉₀ was 1.62 mL kg ^-1 min ^-1. The EbbTM protocol was associated with measured VO _2max (ρ = 0.48; ρ = 0.01) and was positively correlated with moderate- (ρ = 0.32; ρ = 0.02), vigorous- (ρ = 0.47; ρ = 0.0005) and moderate-to-vigorous-intensity PA (ρ = 0.36; ρ = 0.009), pedometer steps (ρ = 0.41; ρ = 0.002) and inversely correlated with waist circumference (ρ = -0.58; ρ < 0.0001), body fat (ρ = -0.55; ρ < 0.0001), and right leg endurance (ρ = -0.41; ρ = 0.003). The EbbTM protocol was shown to be reliable and associated with objective measures of fitness and PA in healthy, middle-aged women.