During foot flat, which muscle begins to eccentrically contract?

During the foot flat phase of gait, the gastrocnemius muscle begins to eccentrically contract. This phase occurs right after the heel strikes the ground and signifies the transition from the loading response of the gait cycle to the next phase.

As the foot contacts the ground, the weight of the body begins to shift over the foot. The gastrocnemius, along with the soleus, plays a critical role in controlling the rate at which the tibia moves forward over the fixed foot. Eccentric contraction of the gastrocnemius helps to decelerate the forward motion of the tibia, thereby stabilizing the knee and preventing excessive forward fall. This action is vital to maintain balance and proper joint function during ambulation.

While other muscles may be active during this phase, their role is not primarily focused on managing the transition between the loading response and subsequent phases of gait like the gastrocnemius. Therefore, the eccentrically contracting gastrocnemius muscle is crucial for ensuring proper biomechanical function during foot flat.