Jumping on sand surfaces redistributes loading of the plantar surface to midfoot areas and reduces peak loading

The purpose was to assess plantar mechanical loading on different surface conditions when performing jumps. Twenty subjects performed standardized drop jumps and countermovement jumps both in shoes and barefoot on a rigid surface and barefoot on a sand surface. Flexible insoles of the Pedar Mobile system (PedarX, Novel GmbH) were used for data collection. The foot was subdivided into eight regions where peak pressures and relative loads were derived. Significant differences were found for several foot areas for both, countermovement and drop jumps. For the sand surface, as compared to the rigid surface, peak pressures were significantly reduced in the hallux&2 nd toe, medial/lateral forefoot, and heel but were increased in the medial/lateral midfoot. The relative load shifted significantly from the forefoot to the midfoot area. Substantially different plantar pressure distribution patterns between conditions were observed in jumping. The switch from a rigid to a sand surface is associated with a lower mechanical loading, whereas switching back from sand to an indoor surface potentially increases this loading. Our results show that the observed pressure distribution patterns for different surfaces align with other tasks like playing soccer/running, are in a typical range for these sports and entail a comparable mechanical loading.