Optimizing kicking performance in a 22 years old semi-professional football player.
There are 2 main types of kicking techniques described in the literature, when kicking a ball in football; the instep kick and side-foot kick. Biomechanical studies have shown that the two kicks are very similar with only small difference in terms of pattern and magnitude of muscle activation (1). Kicking is an open kinetic chain motion, which has a proximal to distal sequence of segmental movement and muscle pattern (3). Brophy et al (2007), divided the instep kick into 5 phases which are delimited by 6 events (Figure 1). The main muscles involved during kicking can be classified into agonist, antagonist, fixators and synergist, an overview of these can be found into table (1). Kicking a ball in football is one of the most frequently used skill and is the most important offensive skill to score goals (7,8,). Therefore, improving kicking skills should be a primary focus to improve football performance. Kicking performance measured by ball velocity and distance depends on several factors such as maximal strengths of involved muscles, rate of force development, neuromuscular coordination, linear and angular velocities of ankle in the kicking leg, and the level of coordination between agonist and antagonist (2).
Figure 1 The instep kick divided into 5 phases delimited by 6 events (1).
|Table 1: main muscles involved in kicking and their role.|
Anterior oblique sling (external internal oblique and adductors),
|Fixators||Supporting leg: Quadriceps, gluteus medius, minimus, maximus|
2. Muscle anatomy and Physiology
2.1 Muscle Physiology
Skeletal muscle function has 3 basic performance parameters; movement production, force production and endurance. The production of movement and force are an outcome of muscle contraction trough the sliding filament theory, which are influenced by several factors (37).
2.1.1 Sliding filament theory of muscle contraction
Muscles are made of muscle fibres which produce contraction. Muscle fibres are made of myofibrils, which are organized into functional unit called sarcomeres. Contraction of a whole muscle is the sum of singular contractions occurring within the individual sarcomeres, this is achieved through the sliding filament theory where contraction results from the formation of cross-bridges between the myosin and actin myofilament causing the actin chain to “slide” on the myosin chain (37)
2.1.2 Length-tension relationship
Tension produce by muscles depends on the sarcomere length at the time of stimulation, which determines the overlap between actin and myosin. This is because force production is largely determined by the number of cross-bridges that form. When the sarcomere has an optimal length with maximal overlap between actin and myosin greatest level of active tension can be developed. Force production is impaired when the sarcomere is shortened or lengthen too much (see fig 2) (13, 14). Length tension relationship influence the ability of muscle fibres to develop force and therefore play an important role in maximal muscular power production (12). Biomechanical studies showed that during kicking the hip extends to up to 29° (25) and the knee flexes to an average of 82.4° (1). Therefore, it is important to train trough these range of motion to improve muscle function through its entire length tension-relationship.
Figure 2: demonstrating the length tension curve of a whole muscle (37)
2.1.3 Force- velocity relationship
Force-velocity relationship during concentric muscle contraction is characterised by an inverse hyperbola relationship (fig 3) (11). This means that as the velocity of concentric muscle action increase the force which is capable of being generated decreases. This is because the total number of cross-bridges attached decreases with increase velocity of muscle shortening. Improvement in maximal power output of a muscle can be achieved through increasing maximal isometric force or maximal velocity of shortening (12). During the forward motion of kicking the hip accelerates up to 745°/sec and the knee velocities can reach up 1720°/sec (26). Some part of the training should therefore be done through similar velocities.
Figure 3: demonstrating the relationship between contractile force and the velocity of contraction in isometric and concentric contraction (37).
2.1.4 Types of muscle contraction
Muscle contraction can be classified as isotonic or isometric.
In an isometric contraction the muscle as a whole does not change length and the tension produced never exceed the load. There are two types of isotonic contraction, that is concentric and eccentric. In a concentric contraction, the muscle tension exceeds the load and the muscle shortens. In an eccentric contraction, the peak tension is less than the load, and the muscle lengthen (20).
The stretch-shortening cycles (SSC) refers to a successive combination of eccentric and concentric muscle contraction (15). SSC has been shown to generated higher force and power than during a concentric action only (16, 17). Therefore, maximal muscular power is superior in movement involving a SSC (18, 19). Kicking involve a SSC of the iliopsoas, quadriceps and the anterior oblique sling, which lead to a more powerful kick as forces are transmitted from the whole body to the leg (27).
2.2 Muscle anatomy
The ability to generate maximal power during a movement is dictated by the contractile capacity of the muscles involved. The contractile capacity is mainly influence by fibre type composition and architectural features (12). A review of these features and the functional role of the main muscles (agonist anatagonist) involved in kicking can be found in table 2.
2.2.1 Muscle fibres
There are two main types of muscle fibres; type I and type II. Type II have a greater capacity to generate power per unit cross sectional area (21, 22). They are characterised by their large diameter and contain densely packed myofibrils, large glycogen reserves and relatively few mitochondria. In contrast, slow fibres have only about half the diameter of type II fibres, take longer to peak tension and are surrounded by an extensive capillary and mitochondria (20). Muscles with a high percentage of type II fibres display greater maximum power in comparison to muscle with a high percentage of type I fibres (21, 22).
2.2.2 Muscle Architecture
Muscle architecture, which refers to the arrangement of muscles fibres, has marked effect on a muscle’s ability to produce movement and generate force. Fibre arrangement can be placed into two categories parallel and pennate (10).
In parallel-fibered muscles, muscle fascicles are arranged along the line of muscle force action (9), generally these fibres are long and can shorten more than pennate muscles and thus produce a larger joint excursion (10).
In pennate muscles, fascicles are attached to the tendon at an angle and thus fibres lie at an angle to the line of action of the entire muscle (pennation angle). The main advantage is that more muscle fibres can be filled into a given volume of muscle and thus increase force production, however the muscle fibres are shorter and have fewer sarcomeres than parallel muscle, so their maximum displacement and velocities are smaller. The pennation angle is subject to change, the angle increase with muscle hypertrophy and decrease as muscle size decrease. There is a positive correlation between the pennation angle and muscle force (9).
|Muscle||Contraction type||Muscle Architecture||Fibre type||Functional role|
|Gluteus maximus||Concentric from preparation to backswing phase
Eccentric from leg cocking to follow trough
||48% Type II
|(1) Extend the hip to create a tension arc and prepare for the kicking
(2) During the kick eccentrically contract in order to control hip extension
|Hamstrings||Concentric from the preparation to the cocking phase
Eccentric contraction from the acceleration phase to the follow trough phase.
|Biceps femoris (long head)||
||53 – 55% Type II (24)||(1) Collectively the hamstring assist gluteus maximus in extending the hip to create a tension arc.
(2)They also flex the knee to further create a tension arc as the leg is cocking.
(3)During the kick eccentrically contract to control hip flexion and knee extension.
|Biceps femoris (short head)||
||59% Type II (24)|
||54-60% Type II (24)|
||50-51% Type II (24)|
|Iliopsoas||Eccentric from the preparation to the leg cocking phase, followed by a SSC and concentric contraction during the acceleration and follow trough phase||
||50% Type II (23)||(1)Eccentric control of hip extension in preparation for the stretch-shortening cycle
(2)Powerful acceleration of the hip in order to get maximal velocity of the leg when hitting the ball
|Quadriceps||Eccentric contraction from the preparation phase to the leg cocking phase, followed by a SSC and concentric contraction during the acceleration phase and follow trough||Rectus femoris||FL: 7.59 ± 1.28
PA: 13.9 ± 3.5
PCSA: 13.5 ± 5.0
|57-70% Type II (23)||(1)Eccentric control of hip extension (Rectus femoris) and knee flexion in preparation for the SSC.
(2)Powerful acceleration of the knee in order to get maximal velocity of the leg when hitting the ball.
(3) Eccentric contraction of the supported leg to absorb the impact from landing and create a stable platform for the kicking leg.
|Vastus lateralis||FL: 9.94 ± 1.76
PA: 18.4 ± 6.8
PCSA: 35.1 ± 16.1
Type II (24)
|Vastus intermedius||FL: 9.93 ± 2.03
PA: 4.5 ± 4.5
PCSA: 16.7 ± 6.9
|Vastus medialis||FL: 9.68 ± 2.3
PA: 29.6 ± 6.9
PCSA: 20.6 ± 7.2
|38-56% Type II (24)|
3. Optimizing the movement and its performance
Research has shown that resistance training improves athletic performance by increasing muscular strength, power and speed, hypertrophy, local muscular endurance and neural adaptation (28). A brief definition of these concepts and their relation to training are shown in table 3. The key factor for a successful exercise program is an appropriate program design based on goal setting via a needs analysis and basic training principles (29). A brief review of training principles shown in table 4. In this setting our goal is to improve instep kicking performance of a football player, where kicking performance is measured by ball velocity and distance.
3.1 Need analysis
A need analysis to rationalized our programming (load, sets, repetitions, and exercise selection) and periodization can be achieved through analysing the function required from the muscles involved during the kicking movement. Kicking occur in 5 phases: preparation, backswing, limb cocking, acceleration and follow through.
The preparation phase includes the approach to the ball and the planting of the supported foot. The role of the supporting leg is to absorb the impact of landing (30) and to provide a stable platform to quickly swing the kicking leg. During this movement, the quadriceps is acting eccentrically to brake the forces and stabilize the leg. Therefore, exercises that involve single leg landing control with enhancement of the braking components are recommended such as single leg landing task maintaining knee angle greater that 50° (31) such as Drop Freeze, but also rear foot elevated split squat.
During the backswing phase and the limb cocking phase the player extend the hip up to 29° (25) and the knee flex to an average of 82° (1) to create a tension arc. It is therefore important to give the player hip extension exercise such as (single leg) dead-lifts, hip thrust but also end range exercise such as donkey kicks and knee flexion exercises such as leg curls.
When the leg starts to move forward it is considered the acceleration phases, which involve a stretch-shortening cycle of the hip flexors (iliopsoas), the quadriceps and the anterior oblique chain to allow a maximal velocity of the lower limb. It is therefore recommended to develop strength, power, and speed of the lower body musculature. This will involve strength exercise such as resisted kicking, squats, leg extension, power exercises such as weighted ball kicking, power clean, ball slam and plyometric training for optimal utilization of the SSC such as Box jumps, skip, two hand side to side throw.
Periodization is a logical method of organizing training into sequential phases and cyclical time period in order to increase the potential for achieving specific performance goals while minimizing the potential for overtraining (33). It is suggested that periodized training are more effective for increasing muscular strength that non-periodized training (32). The exercise program for this athlete will have 2 blocks of 6 weeks. The first one will focus more on strength and the second one on power. The program will include plyometric training along the 12 weeks for optimal utilization of the SSC. A recent systematic review by Ramos et all. 2018 showed that plyometric training and resistance training both had an effect to improve kicking performance in terms of ball speed, however plyometric training had a greater effect (34).
|Table 3: Definitions of strength, power, hypertrophy, muscle endurance, motor recruitment and their relation to resistance training (36).|
|Definition||Load (1%RM)||Goal repetitions||Sets|
|Maximal strength||Strength is the maximal amount of force a muscle or muscle group can generate in a specified movement pattern at a specified velocity.||≥85||≤6||2-6|
|Power||During an exercise power is defined as the weight lifted multiplied by the vertical distance it moved divided by the time to complete the movement. Power can be increased either by moving the same weight faster or by moving a heavier weight at a same speed||Single effort event: 80-90
Multiple effort event: 75-85
|Hypertrophy||Refers to the enlargement of muscle fibres cross sectional area following resistance training. There is a positive correlation between hypertrophy and strength.||67-85||6-12||3-6|
|Muscle endurance||This is the ability of a muscle (muscle group) to sustain repeated contraction for a given load for a certain period of time. This has been shown to improve with resistance training.||≤67||≥12||2-3|
|Motor recruitment||Increased firing rate of overlapping action potential, increased recruitment of motor unit and greater synchronization lead to increased strength and power.||–||–||–|
|Table 4: Principles of training|
|Progressive overload||A training adaptation only take place if the training load is above the normal level. There are two ways to manipulate this (1) is by increasing the training load by increase the intensity and or volume. (2) changing the exercise to a new exercise that the athlete is not accustomed to (35).|
|Specificity||All training adaptations are specific to the stimulus applied. These adaptation are specific to muscle action involved, speed of movement, range of motion, muscle group trained, energy system involved and intensity and volume of training (29). Training should attempt to mimic sporting characteristics and demands|
|Variation||Training variation requires that alterations in one or more program variables be made over time to allow for the training stimulus to remain optimal. Systematically changing volume and intensity is the most effective for long-term progression (29)|
|Accommodation||Refers to the fact that if an athlete performs the same exercise at the same intensity over a long period of time, the adaptation gain from the stimulus will decrease (35).|
|Individualization||Training program need to be individual to the person as different people will respond differently to training stimulus. E.g. are baseline fitness level, previous training history, age, gender.|
|Recovery||Training adaptation occurs when a muscle is recovered fully from previous training and is ready for the next overload training session. Therefore, appropriate recovery time are essentials.|
|Reversibility||Means that physiological adaptation gained from training stimulus with rapidly be lost if the training stimulus is stopped.|
|Table 5: Periodization of training program. lower body training session (L), full body training session (F), plyometric training session (P).|
|Macrocycle (12 weeks) Aim is to improve kicking performance|
|Mesocycle (6 weeks)
Focus on endurance, hypertrophy and strength
Focus on Maximal strength and power
|Microcycle (2weeks) Focus on endurance||Microcycle (2weeks)
Focus on hypertrophy
Focus on Strength
Appendix 1 Exercise program
This is a 12-week training program aimed at improving kicking performance of a young semi-professional football players, who is in off-season. This training program is broken down into 2 blocks of 6 weeks. The first block is focus is to improve strength and the second to improve power. Key performance indicator are ball velocity and distance, which can be measured trough speed gun radar and simply measure the distance from the kicking position to where the ball lands. These will be measured before the 12-week training program starts, at the end of the first 6 weeks block and at the end of the 12-week training program.
This program is divided into 2 blocks of 6-week training with 3 training session a week a, b, c. Training session A should be performed on Monday, B on Wednesday and C on Friday. Before each session spend 10-15 minutes warming up through some light cardio. You should aim to complete all sets and repetitions at the intensity require, which is the percentage (%) of your 1 maximum repetitions (RM) or with perceived exertion scale (RPE). Your 1RM can be tested at the beginning of your first 6 block and 2nd 6 week block by completing the exercise until failure and using the table 1 to evaluate your 1RM. The RPE scale is explained in the table 2. You can record the weight that you used for each set in the blank box next to the exercise in order to track your progression. For session C exercise 1-4 no weight are used, however you can tick fill the box with the amount of repetitions you managed to do for each set.
|Exercise||Week 1||Week 2||Week 3|
|1||Resisted kicking with pulley||5||10||3||75||7||5||10||3||75||7||5||8||3||80||8|
|3||rear foot elevated split squat||5||10||2||75||7||5||10||2||75||7||5||8||2||80||8|
|5||banded kneeling overhead raise||5||10||2||75||7||5||10||2||75||7||5||8||2||80||8|
|1||barbell back squat||5||10||3||75||7||5||10||3||75||7||5||8||3||80||8|
|2||barbell bench press||5||10||3||75||7||5||10||3||75||7||5||8||3||80||8|
|5||twisted abdominal crunch||5||10||2||75||7||5||10||2||75||7||5||8||2||80||8|
|2||double leg vertical jump||3||7||3||7||3||7||3||7||3||10||3||8|
|3||Drop Freeze bilateral||3||7||3||7||3||7||3||7||3||10||3||8|
|5||two hand overhead throw||3||10||3||75||7||3||10||3||75||7||3||10||3||75||8|
|Exercise||Week 4||Week 5||Week 6|
|1||Resisted kicking with pulley||5||8||3||80||8||5||6||3||85||9||3||8||3||75||7|
|3||rear foot elevated split squat||5||8||2||80||8||5||6||2||85||9||3||8||2||75||7|
|5||banded kneeling overhead raise||5||8||2||80||8||5||6||2||85||9||3||8||2||75||7|
|4||mid thigh pull||5||8||2||80||8||5||6||2||85||9||3||8||2||75||7|
|5||twisted abdominal crunch||5||8||2||80||8||5||6||2||85||9||3||8||2||75||7|
|1||Split squat jump||3||7||3||7||3||7||3||7||3||6||3||8|
|2||two single leg jump||3||7||3||7||3||7||3||7||3||6||3||8|
|3||single leg Drop Freeze||3||7||3||7||3||7||3||7||3||6||3||8|
|5||two hand side to side throw||3||10||3||75||7||3||10||3||75||7||3||6||3||75||8|
|Exercise||Week 7||Week 8||Week 9|
|1||weighted ball kicking||5||6||3||85||7||5||6||3||85||7||5||4||3||90||8|
|5||Barbell Hip thrust||5||6||2||85||7||5||6||2||85||7||5||4||2||90||8|
|1||barbell front squat||5||10||3||75||7||5||10||3||75||7||5||8||3||80||8|
|2||single arm dumbell bench press||5||10||3||75||7||5||10||3||75||7||5||8||3||80||8|
|3||sumo dead lift||5||10||2||75||7||5||10||2||75||7||5||8||2||80||8|
|5||isolated cable rotation||5||10||2||75||7||5||10||2||75||7||5||8||2||80||8|
|1||cycled split squat jump||3||7||3||7||3||7||3||7||3||10||3||8|
|2||single leg box jump||3||7||3||7||3||7||3||7||3||10||3||8|
|3||single leg Drop Freeze||3||7||3||7||3||7||3||7||3||10||3||8|
|5||two hand side to side throw||3||10||3||75||7||3||10||3||75||7||3||8||3||80||8|
|Exercise||Week 10||Week 11||Week 12|
|1||weighted ball kicking||5||4||3||90||8||5||3||3||95||9||5||3||3||95||9|
|5||Barbell Hip thrust||5||4||2||90||8||5||3||2||95||9||5||3||2||95||9|
|1||barbell front squat||5||8||3||80||8||5||6||3||85||9||3||8||3||75||7|
|2||single arm dumbell bench press||5||8||3||80||8||5||6||3||85||9||3||8||3||75||7|
|3||sumo dead lift||5||8||2||80||8||5||6||2||85||9||3||8||2||75||7|
|5||isolated cable rotation||5||8||2||80||8||5||6||2||85||9||3||8||2||75||7|
|1||cycled split squat jump||3||10||3||8||3||12||3||9||3||12||3||9|
|2||single leg box jump||3||10||3||8||3||12||3||9||3||12||3||9|
|3||single leg Drop Freeze||3||10||3||8||3||12||3||9||3||12||3||9|
|5||two hand side to side throw||3||8||3||80||8||3||6||3||75||9||3||6||3||75||9|