Intra- and Inter-muscular variations in hamstring architecture- Kellis (2018)

So, it has been quite a while since I put together a blog post for my own site as I have been busy with other projects for people like The Physio Network, @FMPA and Vald Performance which has been great, and thank you to those people for accepting my ramblings on various different topics!

I sat down today and read a new paper by Kellis (2018) which is a narrative review of the intra- and inter-muscular variations in hamstring architecture. It might not be everyones cup of tea in terms of light reading, but the hamstring “enthusiast” in me (prefer that term to geek!) really enjoyed it and took a lot from it, so I thought it would make a good piece to put up on here.

The paper is a comprehensive review of all of the hamstring musculature, but for the purposes of this blog I will just discuss the Biceps Femoris Long Head, as this is the muscle that we see injured most commonly within elite football. So from an architectural point of view, why might we see so many BFlh injuries, especially up towards the proximal musculotendinous junction? Below I’ve summarized some of my key take home points from the paper;

  1. Variations in architecture proximally

The BFlh displays differences in architecture throughout the length of the muscle, with longer fibers and a greater pennation angle proximally. An assumption could be made that this means greater force production is possible at the proximal end of the BFlh, and so modeling studies would suggest that there is greater strain placed on the tissues, which could account for the greater number of injuries in this proximal region.

  1. Aponeurosis Differences

BFlh has one narrow aponeurosis at it’s proximal end, and one wide aponeurosis at it’s distal end. Simulation studies have suggested that this formation exposes the areas adjacent to the MTJ to greater strains than those muscles such as the semitendinosus and semimebranosis which have two wide aponeurosis. This may therefore again predispose the area to greater risk of injury.

  1. Shorter Moment Arm Around the Knee

As the BFlh has a shorter moment arm around the knee it is suggested that it has a lower torque capacity than the ST and SM. This means that the BFlh must exert greater force compared to the other hamstring muscles when actively lengthening in the same time frame. It must be noted however that this is assuming that all hamstring muscles have an equal contribution to torque around the knee.

 

These are just three very brief comments from a very comprehensive paper put together by Kellis for the Sports Medicine Journal, but hopefully it gets peoples attention and points them in the direction of a great narrative paper. The link for which is here.

Thanks for reading!

 

@PreventionPhys

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