KPI in Soccer and the role of the Centre Back

Let’s identify 3 KPI in soccer and see how we can improve.

Soccer is a high-intensity team sport with high contact between athletes and recovery time between actions.

It requires a wide variety of physical abilities such as:

• Speed
• Agility
• Power
• Strength
• Stamina
• Acceleration

As far as tactical abilities, a soccer player needs:

• Vision
• Awareness of space
• Anticipation
• Organization
• Communication

And some of the most important psychological abilities such as:

• Concentration
• Motivation
• Attitude
• Body language

Players in different positions will need to have different skills. 

The centre back is a delicate position, being the last athlete that separates the opponent’s striker and the last player of his team, the goalkeeper.

Before proceeding, make sure to read my full article regarding strength trraining for soccer.

The centre back doesn’t often sprint for more than 10 to 20m. In fact, in soccer, 96% of sprints are shorter than 30 meters, and 49% of them are less than 10 meters. (Wisløff, U. et al., 2004)

The centre back finds himself often in the position of having to tackle the striker or run after him during a counterattack, anticipate the opponent and hit the ball with the head for a corner kick or a long pass of the opposing team.

A good centre back often has high awareness and vision and is capable of intercepting an opponent’s pass from the midfielders to the striker.

For these reasons, we will further discuss 3 main KPI in soccer for the centre back in soccer:

1. Defensive header
2. Interception 
3. Running after the striker

1) The defensive header

The centre back needs to have great positioning on the field, vision, and physical qualities such as great acceleration and vertical jump to hit the ball first, anticipating the opponents.

As strength and conditioning coaches, we are mainly interested in the physical qualities that make the vertical jump a great centre back.

Vertical jumping consists of the correct use of the stretch-shortening cycle, that utilizes the kinetic energy that is absorbed during the eccentric contraction and rapidly reversed into a powerful concentric action.

The quick isometric contraction that separates the eccentric from the concentric needs not to leak any energy to produce a higher jump.

The vertical jump highly depends on the max and explosive strength of the lower limbs, and on a correct and effective force transmission at the core level to provide enough stability, since the jumps are generally accompanied by disturbance by other players, for example, the opponent’s striker.

The centre back mainly needs a good hip and knee flexion and extension pattern to produce high vertical forces.

The velocity has to be extremely fast, which is why the rate of force development is crucial to produce high power output and therefore a high vertical jump.

The main muscles used are the glutes, quadriceps, the core and stabilizers. Muscles of the foot, the soleus and gastrocnemius also need to be strong, since the power output at the ankle joint can reach a high power output of 3500W. (Umberger, 1998).

The jump follows a distal to proximal pattern by activating the hip joint, followed by the knee joint and finally the ankle joint, resulting in a triple extension of the lower limbs.

The movement of the legs is the most important factor in this skill. (Kristensen et al., 2004)

Energy demands for the vertical jump are mainly anaerobic: the vertical jump is an intense and powerful, short-duration effort, mainly fueled by the PCr system.

The centre back also needs continuous ATP production from the aerobic system, since he needs to perform multiple vertical jumps and other high-intensity efforts during a 90 minutes game.

A defensive header by the centre back may happen multiple time during a game.

The strength & conditioning coach also has to consider that the vertical take-off might be single-leg or double-leg and is often done in different directions: a defensive header might happen while jumping forward, backwards or laterally, making the timing, vision and stability of the athlete essential.

He will need to focus, to improve the defensive header, on physical qualities such as max strength and power of the lower limbs with exercises such as the squat and trap bar jumps which closely mimic the needed movement and coordination while improving the power output and jump height for a better defensive header.

2) Ball interception

Unfortunately, we don’t have any scientific literature on ball interception, probably because it is a sport skill mainly driven by tactical and psychological abilities such as concentration, motivation, attention and anticipation.

How can a strength & conditioning coach improve a centre back ability that is mainly awareness driven? By making him a more reactive and explosive athlete.

The central nervous system and the muscular system have to work together at high speed to make the body follow the decision from the brain.

By improving the athlete’s quickness, reactive strength and early rate of force of development, we can make sure that the physical qualities are not the issues if the centre back decides to anticipate and intercept the ball and fails.

Generally, the player intercepts the ball by sprinting forward or laterally with high horizontal forces.

The movement needed can be multidirectional, every single joint in the body can be called to move in multiple planes, depending on the positioning of the player, of the opponent, the direction and speed of the ball and the action of the defensive player needed.

The velocity of the movement has to be as high as possible: not intercepting a pass in soccer may be risky, but trying to intercept and failing to do so is often much worse.

The defensive player may leave the striker alone in front of the goalkeeper if he tries to intercept an assist and misses the ball. For this reason, improving forward and lateral acceleration, more than speed, is vital for a centre back.

The power output and early RFD needs to improve: we can work on the right side of the force-velocity curve and improve maximal speed of movement, using both horizontal and vertical forces, such as hip thrusts and band accelerated jumps, box jumps and plyometrics, which also improves reactive strength if we use exercises like the depth jump. We also need to train torso rotation and change of direction with speed drills and bodyweight only training, possibly on the field.

The energy is mainly provided by the PCr system since intercepting the opponent is a high effort action of short duration with fairly long rest tempo.

The player does need to try and intercept the ball multiple times in a game, which is why the continuous ATP provided by the aerobic system is important as well. We should also improve reactivity with exercises that the athlete initiates right after an external cue such as a whistle or a clap by a teammate. 

3) Running after the striker

In modern soccer, the centre back often finds himself having to run after the striker of the opposing team.

During a counterattack, the defensive player has to rapidly accelerate from a standing position to either get to the ball before the striker or to limit his offensive play after a long pass, for example.

To overcome inertia, the athlete needs to exert high forces into the ground rapidly in the opposite direction from which he wants to move.

The correct body angle for pushing forces and high rate of force development (early RFD) are needed to make the start fast and reach high levels of acceleration in a short amount of time.

The initial posture has to be a positive angle with a forward lean at around 45°, with head neutral and by bending at the ankle, not at the hips, initially.

The arms need to be used as a lever to apply forces from the upper body: this has to be a violent action to create the most starting strength possible. The rotation of the arms is created by swinging the shoulders.

The ankles have to be dorsiflexed and the knees strongly bent at the beginning of the acceleration to use the extension power of the quadriceps. Foot placements will be slightly externally rotated to help exert more force with the adductors (Bosch & Klomp, 2005).

Again, the energy is provided by the PCr system since acceleration is a high effort action of short duration with a modest to long rest tempo. The centre back will need to perform accelerations and running after a striker multiple times in a game, which is why the continuous ATP provided by the aerobic system is extremely relevant as well.

The physical qualities that a Strength & Conditioning coach has to train for this purpose are maximal strength and power since there is a strong correlation between maximal lower body strength and sprint performance (Wisloff, 2014), and that acceleration itself is an expression of high power of the lower limbs.

For improvements in acceleration, we can use resisted speed drills to improve the driving phase of acceleration: uphill sprint, sled sprints or partner resisted sprints are all useful tools, using up to 20% of the athlete’s body weight in external resistance.

Power, strength and plyometric training used to improve the vertical jump will also improve acceleration through an increase of peak force and power output but we can further use additional exercises with a horizontal force component such as the hip thrust.

We can also use ballistic jump work to develop concentric power, since for acceleration we won’t be using the stretch-shortening cycle or reactive strength, but mainly relative concentric peak force.

Injury epidemiology

After we have describe the 3 KPI in Soccer, let’s now talk about injuries.

In soccer, they can be caused by a fall, a collision, excessive volume of work, a tackle, poor landing mechanics, insufficient eccentric strength, movement dysfunctions, overuse injury or many other reasons.

To reduce the injury risk, we can reduce the stress for the athlete and improve his motor control and increase his fatigue resistance, tissue quality and neuromuscular strength. 

In soccer, stats show that an elite player may occur in one performance limiting injury per year (Junge, Dvorak, 2012).

Most of the injuries occur at the lower extremities and more than half of knee injuries occur during tackles (Nielsen et al., 1989). There are many types of injuries, such as:

• Sprains
• Joint injuries
• Strains
• Contusions
• Fractures
• Dislocations

A thigh strain is the single most common subtype of injury. of which 65% happen to the posterior thigh (Walden 2015). Often, a muscle imbalance between the hamstrings and the quadriceps (HQ Ratio) is one of the main reasons for these type of injuries (Kim, 2011).

There does not appear to be a different exposure to injury risk for the centre back position compared to the rest of the team. Using the Nordic hamstring curl as an exercise seems to be a good injury reduction modality for the posterior thigh strains. (Van Der Horst, Nick, et al., 2015).

Making the hamstrings stronger and improving the muscle balance between the agonist and antagonist muscles will lead to better muscle recruitment, improved running mechanics, better force absorption and faster rate coding of the central nervous system, improving the physical qualities of the soccer player.

Another common site for injuries in the soccer player is at the foot and ankle. Most of these injuries involve a tackle from the side while the foot is pronated/neutral in the sagittal plane for the weight-bearing leg and plantar flexed/neutral in the coronal player for the non-weight-bearing leg.

These types of injuries are most commonly caused by the tackles that created an excessive eversion or inversion rotation of the ankles (Giza et al., 2003).

A good way to deal with injury prevention in soccer is through the use of assessments of risks such as the functional movements screening (FMS) and additional tests like the hamstring bridge test, calf-raise test, isometric back extension test.

Other important elements to take in considerations are the acute changes in load or volume, insufficient conditioning, and psychosocial and historical factors such as age, time of the season, career mileage and lifestyle of the athlete.

KPI in Soccer | References

• Giza, E., Fuller, C., Junge, A. and Dvorak, J., 2003. Mechanisms of foot and ankle injuries in soccer. The American Journal of Sports Medicine, 31(4), pp.550-554.
• Junge, A. and Dvorak, J., 2004. Soccer injuries. Sports medicine, 34(13), pp.929-938.
• Kim, D. and Hong, J., 2011. Hamstring to quadriceps strength ratio and noncontact leg injuries: A prospective study during one season. Isokinetics and Exercise Science, 19(1), pp.1-6.
• Kristensen, L.B., Andersen, T.B. and S⊘ rensen, H., 2004. Soccer: Optimizing segmental movement in the jumping header in soccer. Sports biomechanics, 3(2), pp.195-208.
• Nielsen, A.B. and Yde, J., 1989. Epidemiology and traumatology of injuries in soccer. The American Journal of Sports Medicine, 17(6), pp.803-807.
• Umberger, B.R., 1998. Mechanics of the vertical jump and two-joint muscles: Implications for training. Strength and conditioning, 20, pp.70-74.
• van der Horst, N., Smits, D.W., Petersen, J., Goedhart, E.A. and Backx, F.J., 2015. The preventive effect of the nordic hamstring exercise on hamstring injuries in amateur soccer players: a randomized controlled trial. The American journal of sports medicine, 43(6), pp.1316-1323.
• Wisløff, U., Castagna, C., Helgerud, J., Jones, R. and Hoff, J., 2004. Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players. British journal of sports medicine, 38(3), pp.285-288.