The list of star players that have suffered injuries to the hamstring muscles over the past seasons is long. From Arjen Robben to Christiano Ronaldo and Paul Pogba. The number of players who haven´t yet been affected by this injury seems much lower. Many active and former players probably know the feeling: You start to sprint and suddenly a sharp pain jumps into the back thigh. Continuing to play is immediately unthinkable. From a muscle strain to a muscle tear or even muscle bundle rupture of the hamstrings, anything is possible. It is clear that the physiological stress limits of the muscle have been exceeded and the player will have to deal with a few days, if not weeks, without soccer.

Looking at the scientific data of soccer injuries it is undeniable that there is a rising trend in the frequency of hamstring injuries over the last few years [1]. A reason for the increased number of hamstring injuries could be the increasing physical intensity of modern-day soccer [2]. In particular, the increased frequency of high-intensity movements, such as sprints and explosive direction changes can exceed the load tolerance of the players in the course of a season.

The Injury Mechanisms

Muscle injuries are usually caused by a direct or indirect mechanism. Direct muscle traumas include bruises, for example due to the dull influence of an external force. A typical example in soccer is a hit on the muscle by an opponent´s knee, also known as a “thigh knock”. Indirect muscle traumas include overextension and muscle overuse without external force [3]. A high number of high-intensity sprint actions towards the end of a soccer match while the player is already in a fatigued state is a typical example of the occurrence of hamstring injury.

In soccer training and matches especially the indirect injury mechanism leads to muscle strains of the hamstrings which is why this mechanism requires special attention.

How hamstring injuries occur

Scientific research has shown that the absolute majority of hamstring injuries in soccer are caused without external forces. For example, during a sprint or sudden change of direction without opponents contact [4]. The injuries usually occur in explosive movements as high forces act on the muscle. A mechanism which brings forward muscle injury is so-called eccentric movement in which the activated muscle is simultaneously placed in a prolonged position [5]. A typical example of an eccentric contraction is the movement of the quadriceps muscle (knee extensor) when going downhill. Here, the muscle has to slow down the body and is lengthened by the flexion movement of the knee at the same time. A similar procedure can be observed in sprints in the back thigh muscles of the swinging leg: Shortly before the foot touches the ground, the hamstrings have to slow down the forward swinging lower leg and lead them to the ground - the hamstrings have to work eccentrically in a prolonged muscle state.

"Fatigue increases the likeliness of Hamstring injuries!"

The most susceptible to injuries movement phase of the hamstrings during a sprint action seems to be at the end of the swing leg phase, just before it passes to the stance phase [6]. This is underpinned by the following argument: Another possible traumatic movement phase for the hamstring muscles during a sprint is the change from an eccentric to a concentric muscle contraction phase, also called stretch-shortening-cycle, such as at the end of the swing leg phase. This is when the hamstrings have to actively slow down the forward swinging lower leg in a prolonged muscular state and then actively shorten themselves to bring the foot to the ground [7].

Important! Hamstring injuries are facilitated by the interaction of various factors, such as fatigue during the end of the match or coordination disorders within the muscle group of the hamstrings [7]. Managers, strength & conditioning coaches and physiotherapists should therefore pay particular attention to the fatigue of their players and integrate appropriate preventive training measures before and during the season.

In our next article, you will learn how to prevent injuries to the hamstrings. Here we will present basic preventive approaches that reduce the probability of injuring hamstrings during a soccer match.

Your planet.training Team