Effects of Reduced Body Weight on Plantar Pressures During Running

Abstract

Research has previously documented reduced ground reaction forces, cadences, and stride lengths when using lower body positive pressure (LBPP) treadmills. However, it remains unknown how running on LBPP treadmills alters plantar pressure distributions. PURPOSE: To examine differences in plantar pressure when running on a LBPP treadmill at different levels of body weight (BW) support. METHODS: 10 healthy, recreationally active individuals (sex: 4 M, 6 F; age: 21 ± 2.5 years) participated in this study. Participants ran for 10 minutes at 100% BW, 75% BW, and 50% BW at a moderate intensity (2.29 ± .33 ms-1). During the last 2 minutes at each condition, plantar pressures were recorded using a wireless in-shoe system. Peak pressures under 10 specific regions of the foot were determined. For each region, differences in peak pressure between BW conditions were analyzed using repeated measures ANOVA. RESULTS: For all regions except the hallux, peak pressure was lower in the 50% BW condition than the 100% BW condition (all ANOVAs p < .005). Comparing 100% and 75% BW conditions, the only regions where peak pressure was different was the 2nd, 3rd, and 4th metatarsals (Figure 1). Peak pressure under the hallux was not different between any BW conditions (Figure 1). CONCLUSIONS: While removing BW reduced peak pressures, the effects were region dependent. This has implications for rehabilitation of running injuries. For example, when using a LBPP treadmill for rehabilitation in patient with stress fractures of 2nd, 3rd, or 4th metatarsal, a reduction to 75% BW may be sufficient. However, for other injuries BW may need to be reduced to 50%. Further research is required to investigate how these changes in BW may influence kinematics while running on a LBPP treadmill.