Effect of Uphill Running on VO(2), Heart Rate and Lactate Accumulation on Lower Body Positive Pressure Treadmills

Lower body positive pressure treadmills (LBPPTs) as a strategy to reduce musculoskeletal load are becoming more common as part of sports conditioning, although the requisite physiological parameters are unclear. To elucidate their role, ten well-trained runners (30.2 ± 3.4 years; VO(2max): 60.3 ± 4.2 mL kg(−1) min(−1)) ran at 70% of their individual velocity at VO(2max) (vVO(2max)) on a LBPPT at 80% body weight support (80% BW(Set)) and 90% body weight support (90% BW(Set)), at 0%, 2% and 7% incline. Oxygen consumption (VO(2)), heart rate (HR) and blood lactate accumulation (LA) were monitored. It was found that an increase in incline led to increased VO(2) values of 6.8 ± 0.8 mL kg(−1) min(−1) (0% vs. 7%, p < 0.001) and 5.4 ± 0.8 mL kg(−1) min(−1) (2% vs. 7%, p < 0.001). Between 80% BW(Set) and 90% BW(Set), there were VO(2) differences of 3.3 ± 0.2 mL kg(−1) min(−1) (p < 0.001). HR increased with incline by 12 ± 2 bpm (0% vs. 7%, p < 0.05) and 10 ± 2 bpm (2% vs. 7%, p < 0.05). From 80% BW(Set) to 90% BW(Set), HR increases of 6 ± 1 bpm (p < 0.001) were observed. Additionally, LA values showed differences of 0.10 ± 0.02 mmol l(−1) between 80% BW(Set) and 90% BW(Set). Those results suggest that on a LBPPT, a 2% incline (at 70% vVO(2max)) is not yet sufficient to produce significant physiological changes in VO(2), HR and LA—as opposed to running on conventional treadmills, where significant changes are measured. However, a 7% incline increases VO(2) and HR significantly. Bringing together physiological and biomechanical factors from previous studies into this practical context, it appears that a 7% incline (at 80% BW(Set)) may be used to keep VO(2) and HR load unchanged as compared to unsupported running, while biomechanical stress is substantially reduced.