Foot reaction force measurement during sprint training using insoles with MEMS six-axis force sensors.

Abstract

In this study, we used insoles with MEMS 6-axis force sensors to measure the forces during resisted sled sprint training. The MEMS 6-axis force sensors were placed at the thenar, the hypothenar, and the heel, and 40 m sprints were performed in various conditions: unloaded, with 10 kg sled, 20 kg sled, and 30 kg sled using the insole. The running speed decreased with increasing sled weight, and the ground contact time significantly increased with a sled weight of 30 kg. In vertical reaction force (Fz), the forces at the thenar and heel decreased at 20 and 30 kg, while the Fz at the hypothenar was almost the same regardless of the sled weight. As the sled weight increased, the braking force (Fy) immediately after ground contact decreased, and the propulsive force tended to increase. The ground contact was flat in sprinting with a high running speed, so the reaction forces came from the thenar, hypothenar, and heel. In contrast, when the sled weight was heavier and the running speed was slower, the ground contact was made only with the forefoot, especially with the hypothenar. These results showed that running form in the sled sprint training is similar to the acceleration phase in short distance running, which supports that the training has a good effect on improving acceleration skills.