Mechanism of hamstring strain

[injuryupdate]

This was contributed (via email) by Dr Geoff Verrall:

From my personal experience and the experience of talking to athletes that remember (which is actually not that many) I think the problem (of hamstrings straining) is in swing phase. I actually think it is earlier in the swing phase than late swing with a "error" in the neuromuscular contraction that by late swing is hopelessly lost, incordinate and painful. However I think much of the damage is done as the muscle is in a very vulnerable position and is unable to relax when the foot strikes the ground. I understand there is conflicting laboratory data on this but believe that by late swing most of the force of the hamstring contraction has been already "handled" by the muscle and that in this phase the force is much less. So I believe that when the muscle is fatigued it absorbs less energy so there is progressively more force needing to be handled in late swing. This builds and builds until during a single contraction the force is unable to be handled earlier in the contraction and by late swing that damage is occurring (and hence the pained expressions start) and then when the athlete lands (contact) this compounds the damage. John Orchard and I are trying to look at this via video. I should say I am not an expert in this area but having been a sufferer of this injury a few times I can relate to the thought process of bugger something's wrong then bugger something's hurting and then bugger I should have dived and not landed on my leg as that made it ten times worse.

[injuryupdate]

I have a strong gut feel that hamstrings and quadriceps muscles are strained during ground contact phase, because ultimately it is inability to withstand opposing forces (when at length/on stretch) that strains muscles, and opposing forces are going to be much larger when GRF needs to be absorbed. The interesting debate is that length/stretch is obviously much greater during swing phases. No doubt that it is a stuff up of positioning in the swing phase that leads to the hamstring strain, whether this happens in the air or on the ground. I discuss this at length in the following paper on the website:
http://injuryupdate.com.au/images/re...JSMbiomech.pdf

I have never strained a muscle (besides an adductor playing squash and I had no idea when this happened gait-wise) so don't know how much awareness that an athlete actually gets. Steve Waugh was adamant he felt his calf tear at the exact moment we saw it happen on the stump-cam, but there is a placebo response that is going to make you think this when you see it on video! With respect to quads strains, I am almost certain they don't happen on ball contact when kicking, yet two people who helped out during our quadriceps strain study both have strained a quad kicking an AFL footy and both thought that it happened on ball contact. Jason Akermanis did one at the Lions and told the medical staff he was sure it happened before ball contact (probably on the backswing). 90% of players can't recall when it happened, some don't even know which kick it was.