In a recent clinic given to professional soccer coaches I was surprised to learn that did little on improving the mechanics of the kick. They spent most of their time on strategy and instructing the youngsters on the type of kick needed for the play in question. Their emphasis was not on how well the kick was executed but each player from a biomechanical or kinesiological point of view. Their concern was more with the results of the kick rather the mechanics of the kick.
On the highest levels, spending time on the mechanics of the kick is not, maybe, very important, but the coach typically does not have the time to spend on such details. When a player reaches this level, they should have good kicking mechanics in order to execute the kicks that are needed to play well. However, in the Youth Leagues, spending more time on the mechanics of the kick can often be the difference between making the youngster a successful player that can move on in to the higher leagues, or one who will have to drop out because of his inability to improve.
To assist coaches in teaching effective kicking mechanics, it is first necessary that they understand exactly what constitutes an effective kick whether it be for power or accuracy. To do this, it is necessary to film the youngsters from the front and side and then make cinematograms of selected frames from the video. In this way, the entire kicking sequence can be seen and studied, frame by frame, to see exactly what occurred.
Note that when you view a video tape at regular speed, or study or live action the eye is only capable of seeing 10 “pictures” per second. With a video camera you can record the action at 30 to 50 frames per second and at high shutter speeds to get clear pictures, even of very fast actions. Thus not only can you record more of the action but when you stop and study each frame and make cinematograms (sequence pictures from the film) you can study each frame as long as needed. Looking at a tape or film at regular speed is too fast for the eye to see the details of the action.
That the eye can not catch all the action in a kick can easily be substantiated when coaches, even those who know kicking technique well, look at sequence of pictures of a shot on goal. They can not believe how some of their players execute the kick!
For example, several excellent players who had “good” kicks, instead of making contact on the instep of the foot, turned the foot or leg outward to make contact on the inside of the foot as in a passing shot. They immediately turned the foot back to the front in the follow-through. Thus to the eye it appeared as though the kick was executed well, but in reality it was not.
To better understand the body actions that comprise a mechanically sound kick following is a brief analysis of a side-approach kick, i.e., approaching the ball at an angle to the direction of the kick. As the player approaches the ball he takes a long last stride and places the support leg more or less alongside the ball. (See frame _____) The exact placement of the foot is determined by the type of kick, speed of the approach, time for execution of the shot, etc.
The foot is planted so that the foot is lined up with the direction of the kick. Since the last stride is a long stride, the plant of the support leg is heel first, (See frames ____ and ____) which creates a braking force to stop forward motion. The bracing forces actually stop the lower body and the existing momentum generated in the approach to the ball is transferred to the upper body and it continues to move forward. The foot comes down to make full contact with the ground and the player leans to the side of the support leg to give the kicking leg clearance to come through without hitting the ground.
Because of the long forward stride with the left leg (right footed kicker) the pelvis ends up rotated in a clockwise direction which creates more separation of the legs. And the greater the distance between the thighs, the greater the force that can be generated by the kicking leg which should remain back as the support leg is planted.
The kicking leg then has greater potential kicking force created not only by a longer range of motion, (i.e., a longer pathway through which the kicking leg travels), but also because the hip flexor muscles which will drive the kicking thigh forward are placed on stretch during the last stride. Note that when a muscle is placed on stretch it will contract with greater force.
When the support leg is in full contact with the ground the pelvic girdle then rotates forward until it is square (perpendicular) to the intended line of flight. (See frame ____ As the pelvis approaches the front facing position the thigh of the kicking leg begins its forceful movement forward. The thigh is driven forward fast and vigorously so that the shin “folds up” behind the thigh. This creates a short lever which is more conducive to greater speed of movement. If the leg were kept straight (a long lever) and then brought forward the movement would be much slower.
This action places the anterior thigh muscles (quadriceps) on stretch so that when the thigh starts to slow down and stop, the shin is automatically whipped forward and the leg straightens as it makes contact with the ball. Because of this, the thigh drive is a very important action to produce the force needed to kick the ball hard and/or far. The faster the thigh is driven forward the greater the force with which the shin swings out to contact with the ball.
It should be noted that when ball contact is first made the knee is still slightly bent. (See frame ___) The straightening action continues during contact and when the ball leaves the foot the leg is straight. Thus we see two laws of physics at work in this action, first the short thigh lever for greater speed and a long lever for greater force at the end of the lever when contact is made.