Objective: We tested the hypotheses that walking is more expensive for obese women, and they prefer slower walking speeds that minimize the gross energy cost per distance despite a greater relative aerobic effort [percent of maximal oxygen uptake (Vo(2max))/kg].
Research methods and procedures: Twenty adult women, 10 obese (BMI = 34.1 +/- 3.2 kg/m(2)) and 10 normal weight (BMI = 20.4 +/- 2.1 kg/m(2)) volunteered. To determine the metabolic rate and energy cost per distance vs. speed relationships, we measured Vo(2) and V(CO(2)) while subjects walked on a treadmill at six speeds (0.50, 0.75, 1.0, 1.25, 1.5, and 1.75 m/s; 5-minute trials, with a 5-minute rest period between trials). We measured preferred walking speed on a 50-m section of level sidewalk and Vo(2max) using a modified Balke treadmill protocol.
Results: Walking was 11% more expensive for the obese subjects, but they preferred to walk at similar speeds as normal weight subjects (1.40 vs. 1.47 m/s, p = 0.07). Both groups preferred walking speeds at which their gross energy cost per distance was almost minimized. Obese subjects had a smaller Vo(2max)/kg, so they required a greater relative aerobic effort at the preferred speed (51% vs. 36%, p = 0.001).
Discussion: Obese women preferred a walking speed that minimized energy cost per distance, even though this strategy required a greater relative aerobic effort than walking more slowly. Our results suggest that walking slower for a set distance may be an appropriate exercise recommendation for a weight management prescription in obese adults.