Momentum is about coordination

Today is going to be about technique. Physical and mechanical fundamentals of the technique, which is Biomechanics.

Coordination of partial impulses principle. Does all of that something to do with slalom? Actually it's a concept stolen from athletics throwing events, but I think it does apply to slalom. As a matter of fact, I think it's the mechanical reason, of so called flow of movements.

But let's go back a little. Every sport technique is composed of smaller movements, I'm not going to say whether every movement needs to be one way or another, my opinion is that every coach and athlete must do his own analysis about them. I just want to talk about the coordination between these little movements to archive a higher mechanical efficiency. By the way, that is what technique is about.

What I'm talking about is little force applications which all together produce the final speed or movement. The question here is: Does every one of this force applications help on the desired output, or some are applied on the wrong time or in the wrong direction? Some may be even cancelling between them. Here I'm talking about temporal coordination and force vector. 

Let's try to clear things up with an example about a toy train with a catapult on it:

Tren con catapulta: Train with catapult

Caso: Case

Bola: ball

We can imagine the train going down a ramp and shooting the catapult in a given moment. If that moment is the same as the maximum speed of the train, the resulting speed of the ball will be higher than in any other moment. That's the importance of the proper coordination of two partial impulses. 

Let's take a look of the train from above and change the angle of the catapult (that sounds silly, but how often the impulse from the paddle and from the footrest are not aligned?).

lanzamiento de la bola: ball shooting

del tren: of the train

Obviously the resultant speed of the shooting won't produce as distance in case A than in case B. That explain the importance of the force vectors alignment.

We can try to apply it to slalom, to the going out from the upstream, taking advantage of the eddie. I want to clarify that here I'm not intending to describe the complete kinematic chain of this movement, not even describe all the forces, both external and internad that intervene. I just want to make a case about the principle described above, with a simplified situation. Those matter can give future complete posts.

Forces involved in the getting out from an upstream:
(A) Push on the stern because of the Archimedes principle
(B) Pulling from the paddle
(C) Pushing on the footrest
(D) Leaning forwards

Pedro Henrique Gonçalves, an excellent example of how to coordinate impulses and get very good flow

On the two graphs by the picture, there is represented a higher speed on the up (discontinuous line) if there was a proper coordination (graph on the bottom) or less resultant speed if it wasn't (graph on the top). On the top example one could say that the paddler waited too much to pull after the push from the eddie, and also leaned too early on the way out. Again, I'm not trying to describe the supposed right way out from the up here. 

The proper coordination of these partial impulses is going to produce more speed in one of the toughest point in a slalom run. So, if the athlete manages to do an optimal temporization of the impulses and a correct alignment of the forces, he will get more speed without needing more strength. 

It's the coach's duty to make an athlete find out about it. Nevertheless, the external feedback he can give is never as good as the internal the paddler is getting through his proprioception system. The more experienced the athlete, the more he can rely on this system. And the more expertise, the less he needs to balance, so the more he can care about impulses and its vectors. 

One last thing I'd like to add is about the time where these abilities should be worked on. With experienced paddler we should be careful about the time on the season. The closer to the races, the less we should focus the attention on so internal aspects of paddling.