What are the biomechanical principles of the 'contact' phase of the turn?

The contact phase involves planting the feet, bending the knees and driving with the thighs to generate thrust in the opposite direction. Lyttle (1999, p. 9) explains that the wall contact time has two force production phases: passive and active. The passive force production phase involves the wall impact and the countermovement which is the lengthening of the quadriceps (an eccentric contraction). The active force production phase consists of the shortening of the quadriceps (a concentric contraction) in order to create velocity away from the wall. The forceful extension about the knees and plantar flexion of the feet in the horizontal direction occurs in the active force phase.

A study by Araujo et al. (2010, p. 1180) found that a turn executed with angles of knee flexion between 100°and 120°provides the most favourable peak forces to generate impulse. This angle allows for a time efficient turn without an exaggerated application of force and the subsequent unnecessary expenditure of energy.