Figure 4.

(a) Simulated toe-wall contact forces. A greater ratio of forefoot length to rearfoot length (R/r) permitted greater force at the toe and extended the time of toe contact. (b) Ankle plantarflexor work for different rates of plantarflexion and different rearfoot lengths. At ankle rotation velocities similar to those reported for the sprint start, the shortest rearfoot length simulated permits the production of 3.5 times more work than the longest rearfoot length. At maximal sprinting plantarflexion speeds, the shortening velocities of the muscle fibres are so great that the muscle cannot do work on the wall.