Hamstring training is a topic that I thought I knew about, that was until I sat in a really interesting lecture 3 years ago. In this lecture, the speaker, Franz Bosch challenged what I know about the function of the hamstrings and also how I thought about their movement.
Until this lecture, I though of movement at the pelvis, to equate to the exact same motion at the origin of the hamstring muscle. However I unfortunately had not considered the shape of the pelvis and the fact that the origin of the hamstrings were not in line with the pivot point of the hip joint and so what that means when applied hamstring exercises. When I first qualified as a trainer I would have told you that the best way to challenge the hamstrings to improve their strength for function (not size necessarily), would be to do an exercise that involves a lot of resisted hip extension motions.
Looking now at how the pelvis actually moves, and so how the hamstrings appear to lengthen, it seems that focusing on the muscle was the major problem. This is because, although we can look at a muscle outside of the body, it is really hard to predict exactly what the muscle does inside the body during movement (2). Possibly the best way of training a client would then be to focus on how the movements they want to achieve occur, where they occur and what reactions we would expect from the body as this takes place. For example the role of the hamstrings for soccer player could vary from that of an Olympic lifter, and so you would look to train the soccer player in ways where the hamstrings were active in sprinting (most common hamstring injury in soccer is during sprinting, just before the foot makes contact with the ground or during swing phase depending on which study you read! (3,4)).
I created the following videos to try and show how the origin of the pelvis does not move away from the insertion in a way that you may have been told. If this is true, then to activate the hamstring concentrically, the motion would be need to be end range if the knees were straight and the exercise was coming from hip flexion to hip extension. This is not to rule out the other planes, and it is not to suggest that maybe if you get to end range and then travel in several different planes you would not get a reaction from the hamstrings. However if your goal was to grow the size of the hamstrings, then large range contractions against resistance are where you would aim.
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