Analysing the one-leg jump, part II: What actually happens in the amortization phase

OK, so what does actually happen in the amortization phase? What needs to happen for you to get the maximum height and/or length on your jumps. What makes some people jump so high and look so effortless and what makes some other struggle and collapse at every attempt?

Well, in order to understand these factors we have to first understand what (major) muscles are involved in the one leg jump. So I’m going to list them (some in specific and some in “general” terms):

  1. The calves;
  2. The quads;
  3. The hamstrings;
  4. The glutes;
  5. The hip flexors
  6. The abs
  7. The spinal erectors
  8. The muscles of the “upper body” – the deltoids, the trapezius, the lats etc

┬áLet’s use this video for experimental thought purposes:

Obviously, we have to define where our muscles are :

raptor plant muscle and skeleton position
The position of the muscles and the skeleton overall position in the plant

Now, the first thing I want you to notice is where the ball is in my case: it’s on the right side of the body. Remember, in the previous example of the guy jumping from the free throw line, he had the ball on the left side of the body:

Amortization phase picture
The amortization phase

Also, if you look at the foot position you might think my foot has collapsed forward, but in this situation in my case the screenshot is taken just a little bit later than in his case.

Now we must describe what the muscles do in the plant itself:

  1. The calves prevent ankle collapse in the plant and extend the ankle (plantar flex) at the take-off;
  2. The quads prevent knee collapse in the plant and extend the knee at the take-off;
  3. The hamstrings assist in preventing hip collapse in the plant and assist in extending the hip at the take-off;
  4. The glutes prevent knee&hip collapse in the plant and extend the knee&hip at the take-off;
  5. The hip flexors (psoas and iliac, and rectus femoris) help swing the free leg upwards at the take-off;
  6. The abs stabilize the trunk and create the proper hip position (tilt) for the glutes to properly fire;
  7. The spinal erectors stabilize the trunk and prevent the collapse of the chest;
  8. The upperbody muscles (not depicted) generate the armswing and final take-off momentum.

The problem with this list is that even though these things might be true, the human body doesn’t exist as a collection of separate parts. All these muscles are being coordinated by the same entity – the CNS or Central Nervous System. It is the CNS which coordinates the activity, whether it be tension or relaxation, at the correct moment in time, that these muscles must perform.

So you can look at the muscles as being your “hardware” and the CNS as being your “software”. A stronger hardware will allow you for a faster computer, assuming you have the correct software to take advantage of that hardware in the first place.

The reason why I’m writing this is because all these muscles, at these three joints, the ankle, knee and hip – must collaborate, under what the CNS will tell them to do – do get the job done. And when we as people have faulty mechanics, when we have mobility issues, flexibility issues, firing and recruitment issues, posture issues, injury issues – all these factors change both the hardware itself – how all these muscles behave in a vacuum, in terms of actual anatomical structures – but also in the software of how they work – what the CNS will choose to shut down or overcompensate in order to try to do the best job it can possibly do.

Now, at this point – it gets very complicated. And it doesn’t have to be. We can (and we will try to) get very in-depth in understanding what is going on, but it’s not really necessary for the average trainee.

As an average trainee, all you should care about is getting as strong as possible in the right places (and in the case of the one leg jump those places are the posterior chain, then the calves then the quads) while keeping a low bodyfat and practicing jumping. That’s all there really is to it (I know how this sounds in the middle of dissecting the very thing I’m simplifying right now).

But let’s just take a very common problem: hip flexor tightness. This is maybe the most common problem in the athletic world: the hip flexors become very tight (some say due to prolonged sitting) and since they are the hip FLEXORS, they will tend to shut down the hip EXTENSORS. The hip extensors are the glutes and to a lesser degree, the hamstrings. The last thing in the world you want, as a prodigy one-leg jumper is to have your glutes shut down. The glutes are (should be) the strongest muscles in the body, they are the biggest muscles and they have the best leverage to do the most important concentric movement in the one-leg jump – the hip extension – and contribute to a lesser degree to the KNEE extension (through the ilio-tibial band). So the hip flexors become overly active and tight whereas the antagonists, the hip extensors, become very underactive and lax.

What would then happen in that situation? Well, the CNS will try to use its best possible muscles/levers etc to get you high off one leg. But since the glutes are turned off by the overactive hip flexors, then compensatory mechanics have to take place. Usually, that means the quads are going to be recruited to do the job. But the quads need the knee to go forward in order to load up and then extend the knee (think of a leg extension on a leg extension machine, or a leg press).

Because of all this, not only do you lose the longer lever of the glutes acting all the way up at the hip against the ground to get you up high, but you also stress the knee making it go forward!

This could work (if you have strong quads you might be able to jump high enough) – but you will complain of knee pain after a few jumps and then say “I’m just not made for the one-leg jump”. If you’re not strong enough, you end up here:

Raptor knee collapse picture
This is how knee collapse looks like

And then, obviously, if you’re a natural one-leg jumper, you will say “man my quad strength sucks!” because the area where you’ll feel the collapse occuring will be at the knee, at the vastus medialis area – so logically you will say that the quads are the problem since they “failed” in the plant.

But as you seen, the reason why they failed is not because they are necessarily weak, it’s because they weren’t supposed to be put under that type of tension in the first place if the glutes would’ve actually done the job they are supposed to be doing – extending the hips.

So as you can see, the body plays tricks on you and if you’re not careful about what is going on at all the three joints, the ankle, the knee and the hip – and where your mobility issues lie in – then you might be put on the wrong path in your training.

In this situation, you might think the quad is weak since the break occured at the knee and that therefore you must increase the quad strength to prevent this from happening in the future. So you start training with high bar squats and front squats and leg extensions and leg presses and who knows what other quad-oriented exercises. And getting the quads even stronger will make the CNS depend on them even more, which means that the occurrence of the knee collapse will increase in frequency, while at the same time the occurrence of the faulty movement itself will increase in frequency (because the CNS will choose to use the knee-forward movement more often than in the past for the one-leg jump) – all these subjecting the body to more and more injury chances. If lucky, then you might get some naggy overuse injuries (jumper’s knee etc). If unlucky you might get serious injuries (ACL).

This is why I wrote this article – to increase your awareness of what do all these moments when you feel a certain tension that you didn’t feel before in a certain spot – think about why that is happening and what OTHER areas than the actual area itself might be the limiting factors!

Now in order not to make this post too long I will stop here, but in the next article of this series I will talk about how the calf can give you the same knee-collapse feeling and how overactive hamstrings display themselves (taking over the hip extension role of the glutes).

Leave a Reply