Pitching Fundamentals: Stride
From the pivot and leg lift, the pitcher must drive the back foot off the rubber and stride toward the plate with the leg kick. The length of the stride depends on the height of the pitcher and what feels most comfortable. Too long a stride makes the ball go high; too short a stride makes the ball go low. Have your pitchers experiment to find what works best.
During the striding motion, the stride or the glove side foot remains closed (the stride foot points towards third base for a right handed pitcher ). The moment before the foot lands, it opens and points towards the plate. When the foot opens, the hips open, which brings the upper body through
The toe and heel of the striding foot should land simultaneously ( although the ball of the foot takes most of the shock ), lands in the same spot with each pitch and land softly to avoid any jarring in the delivery. The front knee bends so it can absorb the impact of landing with full weight on the front foot. Keeping the knee straight causes undue stress and strain on the front leg.