I think a lot - a lot - about hamstrings. Why? It is because they are so brilliant and astonishing when engaged properly, and so easy to mis-use. We have designed into our lives a lifestyle where we mostly fail to use them properly. That has major consequences.
We were not designed for chairs - we were adapted by evolution over millions of years to be mostly walking, and if not walking them probably squatting or lying down. So why does that lead me to hamstrings and their misuse?
The 'invention' of the chair in decorative, formal ways dates back to at least 3,000 BCE (we have examples from Egypt). Formal chairs are extremely useful - you can move them and gather them around, they keep you eyes higher and more alert than on the ground, can give you status. Chairs give the system a great 'rest' from being upright, but once we found chairs, we adapted them to work with tables and took to sitting for a very long period, not just for a rest. And once you are working at a chair for so long, you are putting a lot of pressure on the back of the thigh [where the hamstrings are]. And we no longer rose from squatting to upright, but rose from half way up already. That meant that we could pretty much rely on and use the FRONT of the thigh - the quads - to raise us up. Many of us have taken to doing this as our primary, go-to, over-used strategy to keep upright and walk. If you try to get upright from a squat without hamstrings it is impossible; from half way up, it is entirely possible. It is quite hard to rise from a chair using hamstrings as the dominant method, especially if there is a table in front of you as it tends to take the body forward as well.
Using quads as our long term source of standing and walking has significant disadvantages. You can see this if you look at specialist athletes; compare a power-built sprinter with a distance runner. A sprinter often has a magnificent set of bulky quads, used to power the legs at an astonishing rate from a sort of 'chair' start [but leaning the chair shape over and resting on their fingers] , but it cannot be sustained. They rely on fast burning power muscles - those impressive, individual quad muscles straining and displaying wonderfully. But the cost is a visible inability to actually walk well - watch sprinters trying to walk to the start. Some can hardly wrap their legs around each other.
Distance runners by comparison are simply beautiful - they seem to float and hardly touch the ground, and the average speed they can reach and sustain is astonishing. This is because they use the muscles designed to maximise the 'bounce' inherent in using fascia well, giving and receiving energy from the act of running against hard ground. And hamstrings are 'posture' muscles which process energy differently from power muscles, and simply do not tire in the same way. They use hamstrings to minimise effort for maximum effect.
While quads are hugely attached to the femur along almost all the front and side faces of the bone, the hamstrings at the back are hardly attached to the femur at all Instead they attach at their top end to the sitting bones - so famous in yoga - which are actually the lowest, most posterior part of the pelvis. And at about half way down the leg they divide and and then attach onto the lower leg BELOW the end of the femur, either side of the knee, with only relatively small slip of muscle attaching to the back of the femur to control the extension [opening] of the back of the knee and stop the knee opening too far. Most of the effort from a hamstrings is focussed. on opening that knee and lengthening the back line of the body. A contraction of the hamstring brings the lower pelvis closer to the back of the lower leg. It hardly impacts the femur at all, but when the foot is on the ground and your weight anchors it there, the effect is to use your femur as a spacer/strut and the leg becomes straight in response to that contraction. The tissue all around the bones lengthens - so a small contraction produces extension and length. So the hamstrings produce an ENTIRELY different outcome depending on whether the foot is on the ground or not.
Combining your body's weight, the friction of the ground, and - essentially - lengthening the quads at the front, using your hamstrings you end up with a walk which pulls the pelvis upright automatically (as the bottom of the pelvis is pulled towards the ground the top of the pelvis is rotated back/upwards), and which supports the knee (where the hamstrings pull on the top of the tibia it acts as a lasso around the top of the tibia and pulls it safely under the femur). It allows all the tissues in the leg to lengthen, rather than lock down and stiffen. You end up with a longer pelvis/leg/foot system, not a short, tense one. It also enables you to use the knee much better and improve the join action there.
A hamstring powered walk is very, very different process from a quad-based walk. It orchestrates many aspects - your weight, your feet, your pelvis, allowing a walk to happen rather than 'forcing' it to happen. It conserves energy and makes walking seem like 'being walked' rather than something costing effort.
All of which could sound very mechanistic and complicated; what I am aiming to help clients feel is that they have a system - the hamstring/back of the leg system - which is there, is free-ing, lengthening and spacious, and can give them better movement and less wear on their joints. Once someone can feel for themselves a better alternative, they enjoy the sensation and can develop the technique. And their system can stop 'grasping' at getting them upright but simply ride on what is - and has always - been there.
And once the hamstrings can be used properly, then many other parts of your system are freed up to also do something different - from your feet to your head.
So Hamstrings are very often the key to making profound change in how you move and enjoy your body. And that can lead to pain and stress disappearing.
I hope I've explained why the hamstrings are so fundamental and so wonderful and also why we have as a society largely overlooked them - they are not showy or obvious, but they are absolutely foundational to having long term movement health. We really can't work the hamstrings like we work the quads in the gym and show them off, but we can allow them to be the central organising factor in our walking and rising. And that pays off hugely in terms of our comfort and freedom and a sense of potential in our lives.
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An interesting article with information about sustaining speed in distance running: High speed sports: https://engineeringsport.co.uk/2012/08/01/high-speed-sports/