Change in Free-Living Daily Steps does not Affect VO2max Adaptation in Response to a Supervised Aerobic Walking Program in Females Ages 18-45.

We hypothesized that an increase in nonexercise physical activity (NEPA), assessed by daily steps outside of steps accrued during supervised exercise training sessions, would be positively correlated with the change in VO_2max. Females ages 18-45 yr (n = 44; 30 ± 7 yr; 67.7 ± 18.3 kg; 24.9 ± 6.4 kg/m²) completed 36 supervised training sessions on a motorized treadmill (3 sessions/week, 30 min/session) over 12 weeks, at 70% VO_2max (80% max heart rate). VO_2max was assessed at baseline, 4, 8, and 12 weeks, and steps outside of the supervised exercise sessions were recorded daily during each week of training with a hip-worn pedometer. For each participant, linear regression was used to determine the slope of steps/day during the 12 weeks of training. Mean VO_2max increased by 8.2% (30.5 ± 5.9 ml/kg/min to 33.0 ± 5.9 ml/kg/min; range -2.65 ml/kg/min to +6.24 ml/kg/min; P < 0.001). Although mean (± Standard Deviation) steps/day did not change during the 12-week intervention, 25 participants decreased daily steps (-1624 ± 1210) and 19 participants increased daily steps (+1713 ± 1402). The change in VO_2max was not different between the two groups (P = 0.74), and the correlation between Δ VO_2max and the slope of the regression (steps/day) over the 12 weeks was not significant (R² = 0.0005; P = 0.88 for ml/kg/min; R² = 0.008, P = 0.59 for l/min). Change in NEPA, assessed by daily steps, does not impact the VO_2max adaptation observed during a vigorous-intensity walking exercise program in females ages 18-45 yr.