Biomechanical Stages of an in-step soccer kick

Approach angle

Length, speed and angle of approach are the most important aspects of this preparatory movement, which has significant effect on soccer kick success. Kicking from an angled approach up to 45° may increase ball speed (Kellis & Katis, 2007). The approach path is curved and as a consequence the body is inclined towards the centre of rotation. The purpose of the curved step is to ensure the body produces and maintains lateral inclination as the kick is performed, this allows the kicking leg to get under the ball and make better contact with it (Lees, Asai, Andersen, Nunome, Sterzing, 2010).

Plant foot forces (pre-impact)

 

For kicking success the placement of the support foot behind and beside the ball is important. Although there is no general consensus regarding the placement of the ball beside the foot. It has been suggested that the foot should and 5-10 cm behind and 5-28 cm beside the ball.

Swing limb loading (pre-impact)

The kicking leg moves backwards, with the hip extending. The hip is slowly adducted and externally rotated. The hip action makes an important contribution in the early force-producing phase of the kick. Wang (1994) reported that for executing a perfect in-step kick a speedy and large final step approach is crucial for creating a condition that allows the players to increase the velocity of the kicking swing motion. The kicking leg should swing from back to forward as fast as possible.

Flexion of the hip and extension of the knee (pre-impact)

The powerful hip flexors initiate this next phase of the kick. The thigh is swung forward and downward with a concomitant forward rotation of the lower leg/foot. As the forward thigh movement slows, the leg/foot begins to accelerate because of the combined effect of the transfer of momentum and release of stored elastic energy in the knee extensors. The knee extensors then powerfully contract to swing the leg and foot forwards towards the ball (Barfield, 1998). Studies show that there is a relationship between the foot swing velocity and the resultant ball velocity. This implies that to achieve maximal performance, the energy generated before ball contact should not be reduced.

Foot contact with the ball (impact)

Foot-ball interaction during impact is complex as it only occurs for 10ms. There are four phases that are specific to foot to ball interaction.
Phase 1- Centre of ball gravity moves without ball movement.
Phase 2- Start of ball movement until ball velocity exceeds foot velocity .
Phase 3- Start of ball decompression with continuing decrease of foot velocity and further increase of centre of ball gravity velocity.
Phase 4- Foot loses ball contact while foot deceleration and ball acceleration stops (Sterzing, 2010).

A study found that the ball speed was maximised when the area of impact was near the centre of gravity of the foot (Basumatary, 1998).

Follow through

The follow-through serves two purposes; to keep the foot in contact with the ball for longer, and to guard against injury. A longer contact time will maximise the transfer of momentum to the ball and thus increase its speed (Barfield, 1998)