One potential problem with the Nordic hamstring exercise is that it is a bilateral exercise. It has been shown in Aussie rules players that if they have hamstring strength asymmetry of greater than 8% between sides (or >15% in soccer players) they have increased odds of hamstring injury. Therefore, if you have one side stronger than the other, doing a bilateral exercise may selectively recruit more effort from the stronger side and increase the strength deficit between sides. Thankfully, asymmetrical strength is a risk factor that is quite modifiable.
You can get an idea of any asymmetry from a simple hamstring bridge capacity test (see main picture). Do as many lifts of your trunk as you can on each side and compare the result for each side. Remember that differences might be quite subtle based on your strength, perhaps just one repetition could be a 10% difference. Target any asymmetry you find by doing more sets of hamstring bridges on your weaker side. Certainly don’t neglect your stronger side or the Nordic hamstring exercise, just sort out your imbalance at the same time. A large study performed on elite soccer players showed a significant reduction in hamstring injuries for the players who corrected their strength imbalances.
So it should be clear so far that strength is a huge factor in preventing hamstring injuries. But what else can be done? Stretching is a common warm-up practice to help prevent injury. To date unfortunately there has not been any evidence that stretching of the hamstrings can prevent hamstring strains. However, let’s not throw out stretching completely. It has been shown that for players over 25 years of age, a decrease in hip flexor flexibility is an independent predictor of hamstring injuries. Regrettably sports medicine is not yet at the stage where is can reverse aging… however we are perfectly suited to increasing hip flexibility, which needs to be addressed no matter the method utilized to achieve it.
While all of these interventions are great because they are relatively easy to administer and complete, we still have to discuss the most important muscle injury prevention strategy. PRESEASON. Sport specific preseason conditioning of muscles allows them to develop the strength and physiological abilities required to perform that sport. This advice is not just hamstring specific – it works for all muscles required in your sport whether it be soccer, badminton or curling.
So in summary, to prevent hamstring strains: do the Nordic hamstring exercise, balance any strength asymmetries, increase hip flexor flexibility (especially if you are over 25 years old) and most importantly, complete a preseason. Now that you will be able to avoid a hamstring injury the next blog entry will explore other commonly injured muscles.
Croisier, J. L., Ganteaume, S., Binet, J., Genty, M., & Ferret, J. M. (2008). Strength imbalances and prevention of hamstring injury in professional soccer players: a prospective study. Am J Sports Med, 36(8), 1469-1475. doi: 10.1177/0363546508316764
Freckleton, G., Cook, J., & Pizzari, T. (2014). The predictive validity of a single leg bridge test for hamstring injuries in Australian Rules Football Players. Br J Sports Med, 48(8), 713-717. doi: 10.1136/bjsports-2013-092356
Gabbe, B. J., Bennell, K. L., & Finch, C. F. (2006). Why are older Australian football players at greater risk of hamstring injury? J Sci Med Sport, 9(4), 327-333. doi: 10.1016/j.jsams.2006.01.004
van der Horst, N., Smits, D.-W., Petersen, J., Goedhart, E. A., & Backx, F. J. G. (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. doi: 10.1177/0363546515574057