Study Design: Single-group repeated-measures design. Objectives: 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%. Background: 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%. Methods and Measures: 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. Results: Percent maximum heart rate (HR_max) and percent maximum oxygen consumption (VO_2max) 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 VO_2max 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. Conclusions: 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 VO_2max than does forward walking under the same conditions and, if incorporated into sustained training regimens, would be expected to improve aerobic endurance.

J Orthop Sports Phys Ther. 2004;34(2):65-71. doi:10.2519/jospt.2004.0883

Key Words: aerobic conditioning, energy expenditure, gait, rehabilitation, retropulsion