Do strength asymmetries increase the risk for muscle injury?

Today, I am going to discuss the findings of a study published in this month’s issue of the British Journal of Sports Medicine (Fousekis et al., 2011). Muscle strength, flexibility, proprioception, anthropometry and knee stability were evaluated pre-season in 100 football players. The history of previous injuries was also recorded and players were followed for 10 months for injuries occurrence. Asymmetries were defined according to standard criteria. The main findings were

•      Players with eccentric hamstring strength asymmetries and functional leg length asymmetries presented a higher risk for a hamstring muscle strain during the season.
•         Previous injury did not affect hamstring injury occurrence.
•          Players with high body mass, with eccentric strength and flexibility asymmetries presented a higher risk for quadriceps muscle strain.

The new thing with this study is that it examines most of the intrinsic risk factors at the same time. However, there are also some points to consider before applying these findings to other players

• Sample size was small for this kind of research
• Participants were not of high level and this limits the findings’ generalization.

To my opinion, however, the key messages from this study are

1. To evaluate the risk of muscle injury in a player we must consider as many factors as possible at the same time
2. Muscle strength and in particular eccentric strength seems to be related with hamstring and quadriceps muscle strain, at least in non-elite players. The question of whether it is the same in elite level players remains to be answered.

Source

Fousekis et al. Br J Sports Med 45(9):709-714, 2011.