The effects of graded forward and backward walking on heart rate and oxygen consumption.

Abstract

Single-group repeated-measures design. To compare the effects of forward walking (FW) and backward walking (BW) on heart rate (HR) and oxygen consumption (VO2) at treadmill grades of 5%, 7.5%, and 10%. Previous studies of locomotion by humans on a treadmill have reported larger cardiovascular exertion and potential biomechanical benefits of BW as compared to FW for treadmill grades ranging from 0% to 5%. The present study extends these findings by examining the cardiovascular effects of BW and FW at treadmill grades greater than 5%. Twenty-nine volunteers participated in this study. Two subjects were excluded, leaving 27 study subjects (15 females, 12 males; mean age +/- SD, 24.0 +/- 3.4 years). VO2 and HR were measured using open-circuit calorimetry and electrocardiogram, respectively. For both forward and backward walking, subjects performed each of the 3 grades for 6 minutes, during which HR and VO2 were measured. Two-way repeated-measures ANOVAs were employed for inferential statistical analysis. Percent maximum heart rate (HR(max)) and percent maximum oxygen consumption (VO2(max)) increased incrementally for treadmill grades of 5% to 7.5% to 10% for both FW and BW (P < .00001). For each of the 3 treadmill grades, percent HR(max) and percent VO2(max) was 17% to 20% higher for BW than for FW (P < .00001). No statistically significant interactions were detected between direction of walking and treadmill grade. Backward walking on a treadmill at 67.0 m/min (2.5 mph) and grades of 5%, 7.5%, and 10% elicits a greater percent HR(max) and percent VO2(max) than does forward walking under the same conditions and, if incorporated into sustained training regimens, would be expected to improve aerobic endurance.