Hamstring strain injury has remained a significant problem for field sport athletes, despite considerable attention from coaches, medical staff and researchers.
Injury mitigation through strength
One popular strategy for mitigating the risk of hamstring strains is to strengthen the hamstring muscle group, since weak hamstrings have been associated with increased risk. One of the major mechanisms of hamstring strain in field sports is high speed running, although there are a range of other known mechanisms. Therefore much of the discussion about injury prevention exercise relates to sprinting.
There is so much debate about the effectiveness of various hamstring strengthening exercises, and this stems from a number of factors relating to:
- Which of the three hamstring muscles is targeted by the exercise
- Whether the exercise is “hip dominant” or “knee dominant”
- Whether the exercise involves the same contraction type as occurs in sprinting; i.e. eccentric or isometric as shown in the image below. The Nordic hamstring exercise on the left is knee dominant with eccentric muscle contractions. The Single leg prone hold on the left is hip dominant with isometric muscle contractions.
- How the speed of contraction in the strengthening exercise compares to sprinting
- Whether the exercise performed in a supine, prone, or upright standing posture
- How does the exercise range of motion at the hip joint and knee joint compare to sprinting?
Comparing muscle activation
One factor that is rarely discussed is whether a strengthening exercise produces a similar muscle activation pattern to sprinting. In other words, how does the timing of hamstrings firing coordinate with the co-contractions of other muscles around the hip and knee eg. antagonists, synergists? This inter-muscular coordination is usually overlooked when discussing hamstring muscle function, as it relates to sprinting.
It seems to me that all the hamstring strength exercises that are being promoted for their injury prevention benefit don’t come close to replicating the hamstrings muscle function of sprinting. The range of motion at the hip and knee, the contraction speed, and precise neuromuscular pattern of multiple muscles is nothing like sprinting. The only exercise that can duplicate the way in which the hamstrings are loaded in sprinting is sprinting itself. So maybe we need to stop quibbling about the relative merits of hamstring exercises performed in the weight room, and ensure that athletes are exposed to the demands of sprinting by actually sprinting.
A study by Van den Tillaar and colleagues compared the muscle activation of 7 hamstring strength exercises to maximum sprinting.1 In general, as shown in the following figure, the strength exercises induced lower levels of hamstring muscle activation (18-75%) compared to the muscle activation during sprinting.
Finding a better path
This suggests that the strength exercises may not be as effective as maximum sprinting for overloading and adapting the hamstrings. I am not saying we should ditch the strengthening exercises in the weight room, but let’s not worry about searching for that single magic bullet. Rather, I’d suggest a more holistic approach that includes a variety of strength exercises as well as sprinting at maximum speed to aim for a more varied and specific adaptation.