Walking and running economy: Inverse association with peak oxygen uptake

Purpose: The purpose of this study was to test the hypothesis that V̇O_2peak is positively correlated with the regression coefficients of the curve-linear relationship between V̇O2 and speed during a protocol consisting of submaximal walking and running. Methods: Nineteen healthy men (mean ± SD: age = 26.4 ± 6.4 yr, height = 179.9 ± 7.2 cm, weight = 77.7 ± 8.7 kg, % fat = 16.3 ± 7.3) and 21 healthy women (age = 25.6 ± 4.9 yr, height = 167.2 ± 5.4 cm, weight = 61.6 ± 7.7 kg, % fat = 24.0 ± 6.8) underwent an incremental treadmill test to determine V̇O_2peak and on two separate days performed an exercise protocol consisting of treadmill walking on a level grade at 2.0 mph (54 mmin), 3.0 mph (80 mmin), and 4.0 mph (107 mmin) and running at 6.0 mph (161 mmin). Subjects exercised for 5 min at each velocity, with 3 min of rest in between each exercise bout. Pulmonary ventilation (V̇E) and gas exchange were measured breath-by-breath each minute. The average of V̇O₂ values obtained during the last 2 min of exercise for both exercise sessions was used in polynomial random coefficient regression analysis. Results: In the polynomial random coefficient regression analysis for walking speeds only, both linear (r = 0.31, P = 0.053) and quadratic (r = 0.35, P = 0.029) coefficients were modestly correlated with V̇O_2peak. Steady-state V̇O2 during walking at 3.0 and 4.0 mph and running at 6.0 mph was also modestly correlated with V̇O _2peak (r = 0.30-0.48). Conclusions: The results confirm our hypothesis and suggest that, as walking speed increases, the increase in V̇O₂ is positively correlated with the V̇O2peak. Our findings are consistent with the notion that cardiorespiratory fitness and exercise economy are inversely related.