Have you ever noticed that in order to jump your highest, you need a few preparatory steps and a preparatory hop? Have you ever wondered why?
Well, perhaps sadly, I have. I was wondering if this was mere mental preparation – because surely your ability to jump high is going to be dictated by a) the power in your legs on the one hand, and b) your weight on the other hand?
Turns out it’s not.
But why not? And what do the preparatory leg movements do?
If you think the steps are “warming you muscles up” in preparation for the jump you are, in some sense, right – right that you are preparing, but its not the muscles you are preparing but the tendons…
But what are tendons, and what do they do? Good question.
I used to think that tendons were there to help glue the muscles to the skeleton, like the ropes on sailboats glue the sail to the mast and boom. I later realised that they also help make the body more ergonomic by allowing the muscles to be positioned ‘out-of-the-way’ as is the case for your hands; if all the muscles used for your fingers were actually in your fingers they would be rather fat, and not particularly dexterous.
Likewise, if you had to carry your calf muscles in your feet, it would make your feet somewhat heavier and mean you would have to swing lots of weight back-and-forth, up-and-down when you walk and run. Although the calves and thighs still have to move a bit, tendons have allowed the movement to be reduced substantially by connecting these muscle groups to the feet from safer havens further up the leg.
Interestingly (to me anyway), this also explains why some people can’t bend their little finger independently of the second (ring) finger – they are sharing tendons that go right up the forearm!
Ah, but none of that explains why we need to hop before we can jump. True enough – there is another property or function of the tendon that had never occurred to me – until I read “The new science of strong materials” by J.E. Gordon (which I must recommend to scientists of all disciplines, it s a lovely book, I wish I had written it).
So what does a book on material science have to do with tendons? Well, it points out that tendon is unique among materials for its capacity to stretch and in doing so, to store energy. In other words, tendons make remarkably good springs (and explains why animal tendons have been used to make crossbows for thousands of years).
Springs can be thought of as batteries, you put a bit of effort into stretching them now, and the effort is stored there for later use – to shoot an arrow for example.
So, it’s simple really, your legs are like a pair of crossbows: if you pre-stretch the tendons before the jump, and then co-ordinate the energy release to coincide with the power stroke of your muscles, you will jump higher.
And finally, it turns out that a rather good way to pre-stretch the tendons is to hop before we jump. So there you are!
You will probably have noticed that good basket-ballers and high jumpers have taken this further (whether understanding it or not). They run along horizontally at a fair speed (gaining kinetic energy), and then thump down their leg at an angle, transferring all that kinetic energy into their tendons, and then re-cooping it in a vertical jumping burst. I have not done the maths, but I am willing to bet the tendons do much more work than the muscles in the crucial powering phase of the jump.
Something to try:
Have you ever noticed how much easier it is to do 20 jumps in a row rather than 10 jumps with pauses between each one? This is because the pauses between jumps force you to dissipate the energy in your tendons, and so every jump is pure muscle work.
It is also worth noting that even the task of dissipating the energy stored in tendons is tiring for your body – the muscles actually work against the tendons to turn the energy into heat, which is similar to the work your muscles have to do when you walk down stairs.
The really nerdy readers (those after my own heart) will have further noted that this all goes a long way to explain why PE teachers seem to be so obsessed with stretching. You thought it was just to prevent injury? Think again – while it is essential to warm up and down carefully and stretching once warm does reduce the risk of injury, this is largely because stretching improves the condition of your tendons.
So don’t rush through the stretching next time you go to the gym; stretching and flexing your tendons may well do more to improve your athletic performance than muscle work. Tendons deserve a part in any workout, please don’t neglect them – they are, after all, the forgotten workhorse of the body.