Walking and running economy: inverse association with peak oxygen uptake

The purpose of this study was to test the hypothesis that V˙O2peak is positively correlated with the regression coefficients of the curve-linear relationship between V˙O2 and speed during a protocol consisting of submaximal walking and running.

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 VO2peak and on two separate days performed an exercise protocol consisting of treadmill walking on a level grade at 2.0 mph (54 m·min−¹), 3.0 mph (80 m·min−¹), and 4.0 mph (107 m·min−¹) and running at 6.0 mph (161 m·min−¹). Subjects exercised for 5 min at each velocity, with 3 min of rest in between each exercise bout. Pulmonary ventilation (VE) and gas exchange were measured breath-by-breath each minute. The average of VO2 values obtained during the last 2 min of exercise for both exercise sessions was used in polynomial random coefficient regression analysis.

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 VO2peak. Steady-state VO2 during walking at 3.0 and 4.0 mph and running at 6.0 mph was also modestly correlated with VO2peak (r = 0.30-0.48).

The results confirm our hypothesis and suggest that, as walking speed increases, the increase in VO2 is positively correlated with the VO2peak. Our findings are consistent with the notion that cardiorespiratory fitness and exercise economy are inversely related.