Hamstrings injury is the most frequent muscle injury in sports that require high speeds, such as football,1 rugby2 or American football.3 As an example, in football it represents 37% of all muscle injuries.4 What is more, one of the main problems is its high recurrence rate, given that between 12% and 33% of players who have had a hamstrings injury relapse.5 Even though a lot of research and resources have taken place to this matter in the past few years, the occurrence of injuries in football seems to be higher (4% per year), as shown in a study that analysed 36 European clubs during 13 seasons.6
Therefore, due to the impact an injured player has on both an economic and sporting level, a new review5 has recently been published, involving among others, Marc Guitart, member of F.C. Barcelona’s performance department, as well as other experts such as Dr. Julio Calleja or Dr. Pedro E. Alcaraz, in which they analyse the possible mechanisms that determine hamstrings injury.
Running mechanics: in which phase is there a higher risk of injury?
At the beginning of the review, the authors elaborate on the biomechanical patterns of running at maximum or below maximum speeds, emphasising the demands in the long head of the biceps femoris, given that it is the most affected muscle in hamstrings injury.7
As it can be seen in Figure 1, the running cycle comprises two phases: stance and swing. Along the run, the hamstrings go through a lengthening-shortening cycle, and most researchers suggest that at the end of the swing phase hamstrings are more likely to get injured.8,9 This could be due to the fact that (and as it has been shown in different studies), maximum muscle activity occurs at the end of the swing phase.10,11 Moreover, the asynchronous activity of the hamstrings during high-speed sprints seems to be a critical point, because at the end of the swing phase, the biceps femoris activity increases by 67%, while the semitendinosus and semimembranosus by only 37%.12 The researchers speculate that “the massively increased demand in the biceps femoris at maximum running speeds can result in it tending to get injured more frequently than the other hamstring muscles.”