Training Effects On A Lower Body Positive Pressure Treadmill At Different percentages of Body Weight

Abstract

While training on a lower body positive pressure treadmill (LBPP) has become a tool for injury rehabilitation, these devices are now used for training in healthy individuals. While several acute studies have documented lower impact forces and differences in energy expenditure when body weight (BW) is reduced, to date there are no studies examining the longitudinal effect of training at reduced BW. PURPOSE: This study examined the physiological adaptations resulting from an 8-week training program on a LBPP treadmill at three different levels of BW. METHODS: Twenty-four healthy college aged students (age: 25 ±7 years) participated in this study. Participants performed a graded exercise test (GXT) and were placed in one of three training groups: 100% BW, 75% BW, or 50% BW. Groups were balanced based upon the initial maximal oxygen uptake (V[Combining Dot Above]O2max). Each individual trained at ~70% of their peak effort achieved during the GXT. Following an 8-week progressive training program another GXT was performed to assess the effects of training. Primary outcome measures included relative and absolute V[Combining Dot Above]O2max, maximal heart rate (HRmax), and time of GXT. A one-way ANOVA was used to compare the absolute change among groups from pre-training to post-training. RESULTS: A difference in the change scores in relative V[Combining Dot Above]O2max was observed among the 3 training groups (F2,23 = 4.99, p = 0.017). The 100% BW group improved their relative V[Combining Dot Above]O2max (1.71 ± 1.70 ml · min-1 · kg-1) when compared to the 50% BW group (V[Combining Dot Above]O2max -1.41 ± 2.10 ml · min-1 · kg-1) (p = 0.014). Relative V[Combining Dot Above]O2max for the 75% BW group (-0.20 ± 2.02 ml · min-1 · kg-1) was not different than either the 100% BW group (p = 0.131) or 50% BW group (p = 0.443). No significant differences were observed for absolute V[Combining Dot Above]O2 max (F2,23 = 2.91, p = 0.076), HRmax (F2,20 = 2.00, p = 0.164), or time of GXT (F2,22 = 2.09, p = 0.150) among the 3 groups. CONCLUSION: Based on the results, it appears that running at 50% BW results in a slight reduction of aerobic capacity compared to running at 100% BW, while running at 75% BW does not result in any significant change. In order to maintain aerobic fitness, individuals should run with ~75% or more of their BW on LBPP treadmills at moderate intensities.