Comparison of plantar loads during running on different overground surfaces.

The objective of this study is to compare plantar loads during running on different overground surfaces. Fifteen heel-to-toe runners participated in the study. Plantar load data were collected and analyzed using an insole sensor system during running on concrete, synthetic rubber, and grass surfaces at a running speed of 3.8 m/s. Compared with running on concrete surface, running on natural grass showed a lower magnitude of maximum plantar pressure at the total foot (451.8 kPa vs. 401.7 kPa, p = 0.016), lateral midfoot (175.3 kPa vs. 148.0 kPa, p = 0.004), central forefoot (366.3 kPa vs. 336.8 kPa, p = 0.003), and lateral forefoot (290.2 kPa vs. 257.9 kPa, p = 0.004). Moreover, running on natural grass showed a longer relative contact time compared with running on a concrete surface at the central forefoot (81.9% vs. 78.8%, p = 0.017) and lateral forefoot (75.2% vs. 73.1%, p = 0.007). No significant difference was observed in other multiple comparisons. Different surfaces affected the plantar loads while running. The differences may help us to understand potential injury mechanisms.