What are the optimal biomechanics of the Instep drive in Football (soccer)

Figure 1: Six Biomechanical Components of the Instep Drive.

Introduction

Football (soccer) is the most popular sport in the world and is enjoyed by millions of people worldwide. Some fanatics have referred to it as more than sport, rather a way of life, where some cultures see the beautiful game deeply imbedded into their history, some even suggesting they consider football as important as religion (Lees&Nolan, 1998). The most fundamental and frequently used technique for kicking a soccer ball is known as the instep drive, or instep kick. Having an optimal kicking technique is a significant consideration for any player wishing to improve his shooting ability and long range passing. Therefore, understanding the biomechanics of kicking a soccer ball is particularly important for guiding and monitoring the training process. As Kellis et. al (2007) outline, ‘improvement of the soccer instep drive technique is one of the most important aims of training programs for young soccer players’.

To analyse a technique thoroughly, critical examination from the biomechanical perspective provides formidable framework to base investigations on, as it reviews each and every movement pattern in light of producing the optimal result, thus maximsaing positive performance. Lees et. al (1998) has defined biomechanics as, ‘the science concerned with the internal and external forces acting on the human body and the effect produced by these factors’. Exploration of the optimal biomechanics of the Instep drive in soccer will be discussed, with reference to supporting illustrations and a suggested critical analysis of how to produce an optimal technique.

The science of biomechanics contains seven fundamental principles for analysis: stability, maximum force, maximum velocity, applied impulse, direction, angular motion, and lastly angular momentum (Blazevich, 2010). Success of the soccer kick is determined and influenced by several external variables also. For example, the distance of the kick from the goal, the type of kick used, the air resistance, and of course the three core movement phases best described using biomechanical analysis (Kellis et. al 2007).

Table 1: Muscular action during kicking preparation (right-footed kick)
Body part	Action	Muscles
Trunk	Stabilisation of rotation to the right	Abdominals, psoas major, erector spinae and spinal postural muscles
Right hip	Extension	Gluteus maximus and hamstring group
Left hip	External rotation and eccentric extension	Gluteus med, gluteus min, hamstring group and adductor magnus
Right knee	Flexion	Hamstring group and popliteus
Left knee	Eccentric extension	Quadricep group
Right ankle	Plantarflexion	Plantarflexors
Left ankle	Eccentric plantarflexion	Plantarflexors
Left shoulder	Abduction	Middle and anterior deltoid and supraspinatus

Description: Instep Drive

The traditional three phase model for the optimal Instep drive pass technique can be characterised by first approaching the ball from a 45 angle with one or more strides, with placement of supporting/ planted foot positioned beside the ball, with toes lining up to the middle of the stationary ball. The next phase is the point of ball contact, where the kicking leg is taken backwards and the leg flexes at the knee. From here, the rotation of the pelvis is initiated around the planted/ supporting leg by bringing the quadriceps muscle group of the kicking leg forwards, as the knee continues to flex. After this initial action, the quadriceps muscles begin to decelerate until it becomes basically motionless at moment of ball contact.  Simultaneous to this deceleration, the knee vigorously extends to almost maximum extension at the point of ball contact. The kicking leg remains straight through ball contact and begins to flex again during its long follow-through. Quite often, the finishing position of the kicking foot after follow-through is above or of a similar level to the hip. (See Figure 1 & 2 & 3 for visual representation of skills with frame-by-frame isolation)

For a detailed analysis of the instep drive skill in soccer, the skill its self can be broken into six smaller sub components, thus allowing for deeper and more comprehensive examination of the biomechanical principles in place at each stage in the skill pattern (Ghochani et. al, 2010). Proposed six sub-components of the Instep drive as follows:

·       the approach

·       plant-foot forces

·       swing-limb loading

·       hip flexion and knee extension

·       foot contact

·       follow-through.

Video Link: Overview –Biomechanics of Instep Drive

https://www.youtube.com/watch?v=PQjoSNaFf5c

Figure 2: In side view, a frame by frame Illustration of the insteps drive skill in motion break-down.

Figure 3: Key Positions during the Instep drive skill.

a  a)     Maximum hip retraction.

b  b)     Forward movement of the quadriceps muscle group with continued knee flexion.

c   c)      Ball contact

d   d)     Post Impact follow-through

e   e)     Knee flexion as follow through proceeds

Analysis Method: Biomechanical Implications (Quantitative Data Collection)

The optimal method for collecting necessary data revolves around video recording the skill. This image can be slowed to detect intricate body motion, allowing for systematic analysis aimed correcting and altering the current technique against that which is considered to the optimal technique model. The use of technology in the way of motion detection and frame-by-frame break down enables extended examination, thus enabling the athlete to pin point potential parts of the technique to improve. From captured video footage of the skill, data management for velocity, acceleration, angle of ankle, and distance involved in the kicking activity can be easily identified.

(1) Instep Drive: the Approach.

An important consideration relating to the approach, that is all body movement pattern leading up to the point of contact with the ball, is the angle with which the athlete approaches the ball. Studies have shown that the maximum velocity of the shank was achieved with an approach angle of 30 degrees and the maximum ball speed is generated from an angle approach of 45 degrees (Ishii et. al, 2009).  Lees et. al (1998) has provided a viable explanation of this consideration. ‘An angled approach enables the leg to be tilted in the frontal plane, so that the foot can be placed further under the ball, thus making a better contact with it’. An interesting comparison exists relating to the beginning of the instep drive, with either a running approach or stationary. Mean maximum ball speeds of 23.5 m s- 1 when using a stationary approach. By contrast, ball speeds of 30.8 m s- 1 when using a 5-8 stride running approach (Opavsky, 1988).

(2) Instep Drive: Plant-Foot Forces

The planted foot, or non-kicking foot is a significant factor in the instep drive’s optimal technique. It should be be planted firmly, and pointing towards the intended target. Studies have shown that there is a relationship between the position of the planted foot and the direction of the instep drive (Opavsky, 1988 & Lees, et. al, 2013). Thus, if you are aiming towards a set of goals, you planted foot need to resemble that direction prior to contact with the ball. Otherwise this will make for inaccuracy. As Sinclair et. al (2014) outline, ‘the optimal foot plant position for accurate direction is perpendicular to a line drawn through the centre of the ball for a straight  kick’. The planted foot determines trajectory of the ball, it is therefore a major contributing factor to an optimal technique.

(3) Instep Drive: Swing Limb Loading

This component of the instep drive involves the swinging of the kicking leg, as it prepares for the downward motion of to project the ball forward. The opposite arm of the kicking leg is raised in the air, serving as counter balance of rotating trunk position. (Ishii et. al, 2009). The athletes eyes are fixed on the ball at this point, promoting better performance of accuracy. Newton Third of equal and opposite reaction is apparent in this component through the raising of the opposite arm and back swing of the kicking leg. At this point, the plant foot connects with the ground, adjacent to the ball, with an extended kicking leg. The knee is also extending through flexion. Elastic energy is stored in during this movement pattern, as this movement allows for maximal transfer of force through the ball (Ishii et. al, 2009). Eccentric activity is present here, as the hip flexors slow the movement of the kicking leg.

(4) Instep Drive: Hip Flexion/ Knee Extension

This phase involves the movement patter of the hips and knee, the quadriceps are swung forward.

(5) Instep Drive: Foot Contact

‘Ball speed is a measure of kicking success’ (Lees et. al, 2004). Significant variables for consideration include: age, skill level and approach speed all effect the produced ball speed of the instep drive. De Witt et. al (2012) proposes that there are 4 distinct stages to the motion of the instep drive: Withdrawal of the quadriceps and shank during back swing, rotation of the quadriceps and shank forwards, which is a product of hip flexion, when quadriceps angular velocity reduces, there is a corresponding increase in shank angular velocity up to the moment of impact with the ball, and lastly the follow-through.

(6) Instep Drive: Follow-Through

The follow-through phase of the instep drive technique has two fundamental purposes. (1) To keep the foot in contact with the ball for as long as possible, and to guard against potential injury. As is the case with all ballistic movements, a longer conact time with the ball will maximize the transfer of momentum, thus increasing its overall speed (Shan et. al 2005). The body protects itself from injury by gradually dissipating kinetic and elastic forces generated by the swinging, kicking leg after ball contact. A sudden slowing of the leg, that is, not allowing it to move through the ball with sufficient follow-through can potentially increase the risk of hamstring strains/ tears (Anderson et. al, 1994)

Table 2: Muscular action during follow-through (right-footed kick)
Body Part	Action	Muscles
Right hip	Eccentric external rotation, eccentric extension and eccentric abduction	Hamstring group, posterior fibres of gluteus med, quadratus femoris, piriformis and gluteus maximus
Right knee	Eccentric flexion	Hamstring group

Other Factors Impacting Performance

Muscle strength is an important factor in successful execution of the instep drive. Development of muscle strength can be achieved through appropriate resistance training. It is worth outlining that whilst this factor is significant in its contribution to the optimal technique, it is not wholly determined by the improvement in muscle strength. The technical, neuromuscular control of the movement must be developed in conjunction with strength training.

The Answer

The literature reveals that traditional models for biomechanical analysis suggest three core movement components within the skill; the approach, point of contact with the ball, and follow through (Sinclair et. al, 2014& Ismail et. al, 2010). However, questions have surrounding this models authenticity because of its lack of reference to significant factors such as upper body, pelvis and other movement that influence the result of technique. As Shan et. al (2005) discuss, ‘effective soccer kicking uses full-body and multi-joint coordination’. The six-component model suggested by Ghochani et. al (2010) represents an extended, more specific version of the traditional three component breakdown of the instep drive movement pattern.

References

Anderson, D. Sidaway, B. (1994). Coordination Changes Associated with Practice of a Soccer Kick. Research Quarterly for Exercise and Sport. Vol. 65(2), p. 93-99.

Blazevich, A. (2010). Sports Biomechanics – The Basics, Optimising Human Performance. London. Bloomsbury.

De Witt, J. Hinrichs, R. (2012). Mechanical Factors Associated with Development of High Ball Velocity During an Instep Soccer Kick. Sports Biomechanics. Vol. 11(3), p. 382-390.

Ghochani, A.  Tabatabaee Ghomshe, F.  Rezvani Nejad, S. Rahimnejad, M. (2010). Analysis of Torques and Forces Applied on Limbs and Joints of Lower Extremities in Free Kick in Football. Procedia Engineering. Vol.2(2), pp.3269-3274.

Ishii, H, Yanagiya, T, Naito, H. Katamoto, S. Maruyama, T. (2009). Numerical Study of Ball Behavior in Side-Foot Soccer Kick Based on Impact Dynamic Theory. Journal of Biomechanics. Vol. 42(16), pp. 2712 – 2720.

Ismail, A. Mansor, M.R.A. Ali, M.F.M. Jaafar, S. Johar, M.S.N.M. (2010). Biomechanics Analysis for Right Leg Instep Kick. Journal of Applied Sciences, 10: 1286-1292. DOI: 10.3923/jas.2010.1286.1292 

Kellis, E. Katis, A. (2007). Biomechanical Characteristics and Determinants of instep Soccer Kick. Journal of Sports Science and Medicine. Vol. 6(2), p. 154.

Lees, A. Kershaw, L, Moura, F. (2004). The Three dimensional nature of the maximal instep kick in soccer (Part 1: Biomechanics). Journal of Sports Sciences. Vol. 22(6), p. 493.

Lees, A. Nolan, L. (1998). The Biomechanics of Soccer: A Review. Journal of Sport Sciences. Vol. 16(3), p. 211-234.

Lees, A. Asai, T. Andersen, T.B. Nunome, H. Sterzing, T. (2010). The Biomechanics of Kicking in Soccer: A Review. Journal of Sports Sciences. Vol. 28(8), p. 805-817.

Lees, A. Rahnama, N. (2013). Variability and Typical Error in the Kinematics and Kinetics of the Maximal Instep Kick in Soccer. Sports Biomechanics. Vol.12(3), p.283-292.

Opavsky, P. (1988). An Investigation of Linear and Angular Kinematics of the Leg During Two Types of Soccer Kick. Science and Football. pp. 460± 467.

Shan, G.  Westerhoff, P. (2005). Full-Body Kinematic Characteristics of the Maximal Instep Soccer Kick by Male Soccer Players and Parameters Related to Kick Quality. Sports Biomechanics / International Society of Biomechanics in Sports. Vol.4(1), pp.59-72

Sinclair, J. Fewtrell, D. Taylor, P. Bottoms, L.  Atkins, S.  Hobbs, S. (2014). Three-Dimensional Kinematic Correlates of Ball Velocity During Maximal Instep Soccer Kicking in Males. European Journal of Sports Science. Vol. 14(8), p. 799 – 805.