Cardiorespiratory Responses During Uphill Versus Downhill Treadmill Walking in Healthy Individuals

BACKGROUND: At a given treadmill speed, increases in grade serve to augment the associated energy cost. However, few data are available regarding the aerobic and myocardial demands of treadmill walking using a negative gradient. PURPOSE: To compare the cardiorespiratory and hemodynamic responses to treadmill walking at a positive versus negative gradient (± 3.0%), at a constant speed (3.0 mph). METHODS: Apparently healthy individuals (n = 10; 2 men, 8 women; mean ± SD age 28.1 ± 11.1) participated in the study. During the exercise bout, subjects walked at a positive or negative gradient, 3.0 mph @ 3.0% gradient versus 3.0 mph @ -3.0% gradient for 5:00 minutes to assure a steady-state response. Directly measured oxygen consumption (VO2), heart rate (HR), blood pressure (SBP/DBP), and rating perceived exertion (RPE; 6-20) were assessed and averaged over the final 2 minutes of exercise. The subject rested for 5-10 minutes to allow their hemodynamic responses to return to baseline values, then repeated the protocol using the opposite gradient. The order presentation of workloads was randomized (uphill then downhill, or vice versa). RESULTS: HR, SBP, rate pressure product (RPP), RPE, and VO2 were significantly higher during uphill versus downhill walking. In contrast, DBP was comparable for both workloads. Selected responses (mean ± SD) are summarized in the table below:TABLECONCLUSION: Our findings suggest that at a fixed treadmill speed (3.0 mph), adjusting the gradient in a positive versus negative direction (± 3.0%) results in a higher aerobic requirement (∼ 1.2 ± 0.8 METs) for the former. Similarly, the cardiac demands and perceived exertion responses, as reflected by the RPP and RPE, respectively, were greater during uphill walking.