Arm action is critical in relation to sprint performance. The arms work in opposition to the legs. When the left arm goes forward the right leg goes forward and vice-versa. The shoulders are completely relaxed with the swing coming from the shoulder joint. The shoulders stay square to the direction of the run. The swing is powerful but relaxed. On the upswing, the hand rises to a point just in front of the chin and inside of the shoulder.
The arm angle is about 90 degrees or slightly less. During the downswing, a straightening of the elbow corresponds with the longer lever of the driving leg. When the arm swings down it will open slightly as it should be next to the thigh. The elbows remain close to the body. Very important again, do not force or tense shoulders or arms. Arm action precedes leg action. As the arms move faster the legs move faster.
*Note body lean comes from the ground and not from the waist.
The lean is a result of displacing the center of gravity in the direction you are sprinting. Leaning by bending the waist is detrimental to proper mechanics. During the acceleration phase the body has a slight lean. At maximum velocity the torso should be close to erect. Athletes need to concentrate on complete extension of the hip and knee joint as the foot pulls the hips over and high knee pickup of the recovery leg.
The head should be in line with the torso and the torso is in line with the legs at all times. The head remains in a static position. Do not sway the head. The jaw remains loose and relaxed. Do not bite down or clinch your teeth while sprinting.
Do not run on toes. The toes have no power or stability. Remain on the balls of the feet and push against the ground. Do not reach for the ground. The recovery leg lands underneath the hip. If the foot lands in front of the hips, this will decelerate the athlete.
The foot maintains a dorsiflexed position except when the foot makes contact with the ground. The drive leg is fully extended while the recovery leg is shortened as it passes by the knee. This creates a shorter lever which moves faster. The recovery leg lands underneath the hips.