An Ode To Kicking Part II

In part I, we started our exploration of kicking and introduced the idea that one of the most important functions of kicking is to counter-balance the forces created by the upper body. An implication of this idea is that there is an optimal way to kick, and more is not necessarily better.

However, that’s not to say that propulsion is not created, or that it’s not possible to increase the propulsive contribution of the kick. The question is HOW do we facilitate this improvement, as some strategies are going to be a lot more effective than others.

Getting Propulsion

With the above observations in mind, we can conclude that the legs do something and they must be conditioned to kick throughout a race.

What if we want to increase propulsion?

Let’s assume we can get propulsion from flutter kicking during freestyle and backstroke. Here's how we can get more out of the kick.

Kick at a faster rate. Kicking faster all create more force. However, you can only move the legs so fast before the timing between the kick and the stroking rhythm is disrupted. Because the timing of the kick is directly tied to the arm action, you can’t just kick more times per second. While you could outkick the arm action, this is going to disrupt rhythm and timing, and that is going to cause more problems than it will solve. To get more propulsion, you need to find another solution, unless the arms are going to move faster as well.

You can move the legs through a greater range of motion and keep the same kick rate. If you move the legs through a larger range of motion in the same amount of time, you should be able to create more propulsion. This sounds good until you consider that moving the legs through a greater range of motion means dropping the feet deeper in the water.

While this might create more propulsion, it will definitely create more drag. There will probably not be a net benefit, and bigger kicks will definitely create more fatigue. A bigger kick isn't going to work.

An important implication so far is that swimmers can only kick so fast and so hard and still swim within the rhythm of the stroke. Enhanced fitness will not allow swimmers to ‘out kick’ their stroke. However, enhanced fitness can be beneficial in other ways, as we’ll see below.

If swimmers want more propulsion, they’ll need a strategy that is different than simply kicking harder. They’ll need to kick better.

Here’s how.

Improve ankle mobility. Swimmers are pretty limited in their ability to kick faster or kick bigger. There is a pretty narrow window in terms of how much and how fast they can kick. The only real solution is to kick ‘better’ and the easiest way to kick better is to improve ankle flexibility. When accomplished, the foot can be better oriented to move water backwards for longer periods of time, and it can be done in a way that reduces the bend in the knee, which limits drag.

It should come as no surprise that better kickers have really flexible feet and ankles. They simply get more out of each kick.

Improve knee extension. Better kickers tend to have excessive knee extension as well. This is what people refer to as ‘double-jointed’ knees. While this can lead to better kicking, I HIGHLY discourage pursuing increasing this range of motion. It is largely genetic and attempts to change this will likely physically hurt swimmers. And it won’t work as the opportunity for improved mobility is VERY small.

Improve kicking ‘skill’. Better kickers have more a wave like or whip like action to their kicking. This wave starts at the hip and flows down through the leg to the ankle. This is can be seen visually, and has also been demonstrated mathematically. Poor kickers have a more knee-dominant action to their kicking. Importantly, the ability to effectively whip the kick is dependent on ankle flexibility.

To get more propulsion, we can’t necessarily kick harder, we have to kick better. The way to kick better is to improve ankle flexibility, which allows swimmers to kick more from the hip in wave-like action. Otherwise, they’re forced to kick from the knee in order to hold water with the feet.

If this is the case, and we want to improve the propulsive aspect of the legs, we’re going to need different strategies to make that happen. We’re going to need to focus on better, as opposed to simply more.

Are Fast Kickers Fast Swimmers?

When considering the importance of kicking, one of the common arguments is that great kickers are great swimmers.

This is stated by many coaches to defend the role of kicking in a swimming program. While there are definitely significant exceptions, there seems to be a relationship between individuals who are good at kicking with a board and those that are good at swimming fast.

Assuming this is the case, there are two main explanations for this phenomenon. The first is that being better at kicking definitely improves swimming performance. The implications of this observation are pretty obvious. Keep kicking!

However, there is an alternative explanation- the factors that make swimmers good at swimming also make swimmers good at kicking. What are some of those factors?

Great body alignment. Some vessels are built for speed, and some vessels are…not. Swimmers that slip through the water when swimming are going to slip through the water when they kick, with or without a board. They aren’t necessarily better at creating force. They’re much better at reducing resistance. An example of this is the swimmer who can’t do a pull-up yet qualifies for Olympic Trials. No force, just great alignment.

The problem with making this mistake in attributing causation is that all the kicking in the world won’t improve alignment. If you want to improve kicking and swimming, and the underlying driver of performance is alignment, you need to do something very different than kicking. To see how, click here.

Great ankle flexibility. Flexible ankles allow for swimmers to better use the legs to create propulsion, facilitate rotatory forces, and to counter balance the torques created by the arms. A more flexible ankle is going to be much more effective rudder.

Importantly, doing more kicking isn’t necessarily going to improve this factor. While it may result in faster kicking, you haven’t changed the factor that is impacting swimming performance, flexible ankles. That factor has stayed the same.

Great water manipulation. Just like better swimmers can better manipulate the water with their hands, they can likely do so with their feet. The same natural tendencies will show up in the kick. Better swimmers can be better kickers for the same reason, they can manage the flow of the water with their feet just as they can with their hands. The same skillsets are rewarded in both situations.

So, which is it?

I don’t know.

The truth is probably somewhere in the middle in that both factors play a role to some extent.

Regardless, it’s probably not about how skilled a swimmer is at kicking, but how much they can improve their kicking over time. I suspect that getting better at kicking, regardless of the individual’s starting point, can potentially lead to improvements in swimming performance. However, whether these improvements translate into faster swimming is going to depend on the context.

Conclusion

Increasing propulsion is possible, but it’s probably not going to come from simply kicking harder. Swimmers need to learn to kick better, either by improving the effective range of motion through the ankle, or simply executing the kicking action with more skill. We’ll explore how to do both later on in this series.

Let’s assume they a swimmer has worked on their kicking and are now a faster kicker. How do we know if that swimmer is going to SWIM faster? We’ll explore the various considerations in part III.