Some of my friends recently wondered why triathletes tend to have ‘lazy legs’ while swimming, and why Matt, one of them, prefers swimming with a pull buoy between his legs. Well here are my two cents about this.
From my experience, I do not think that a weak kick in swimming is a triathlete specific issue, but more an issue of amateur swimmers.
The kick in front crawl has two purposes: (a) contribute to forward propulsion, and (b) to improve your body position in the water.
Kick for Propulsion
Research done in the 70’s and 80’s seems to indicate that for elite swimmers the kick only increases the swimming speed by 10-15% compared to pulling alone, and only at a very high energy cost (Maglischo, 2003). However, for the kick to be propulsive, the swimmer needs extreme ankle flexibility. Check out these two video clips showing the ankle flexibility of top swimmers:
So, for most amateur swimmers, ankle flexibility limits the amount of propulsion they can get from kicking. In addition, it has long been argued that distance swimmers (this would include triathletes) “should reduce their kicking efforts to conserve energy during their races.” (Maglischo, 2003, p. 120) Compare the kicking action during the London 2012 100 m freestyle finals versus the 800/1500 m freestyle finals.
Women’s 100 m (start around 3:20): http://youtu.be/rhZtZvDdmcc
Women’s 800 m (start around 3:25): http://youtu.be/JHbNKX3VkIM
Men’s 100 m (start around 3:15): http://youtu.be/VO7y41uBdUA
Men’s 1500 m (start around 5:25): http://youtu.be/T5FlDy3YmDQ
For more video clips of Sun Yang check the following link:
Kick for Improved Body Position
According to Swim Smooth (2009), an effective kick should do four things:
I think for most triathletes and amateur swimmers this should be the primary purpose of the kick. However, many triathletes when they hear that they have a weak kick think that they have to kick harder to get more propulsion from the kick when instead they should kick more effectively to balance their body better.
So, here are some of the things I found helpful for teaching an effective kick. Interestingly Swim Smooth (2009) lists the same ideas, so I borrowed some of their wording:
1. Kick from the hip
Many swimmers bend their knees too much whilst kicking – we call this kicking from the knee. This creates large amounts of drag and is probably the number one reason for a swimmer’s legs to sink low in the water. Instead of kicking from the knee you should kick from the hip with a relatively straight leg.
Triathletes can have a real problem here. Cycling and running involve developing power from the knee and it’s easy to carry this habit across into the water. As soon as you bend your knee you present your thigh as a blunt object to the water and you push the water against the flow. (Swim Smooth, 2009)
If you look at David’s YouTube clip above http://youtu.be/hFG6WOPS4ns (Thanks David, for letting me use this) you can see that every once and a while his kick comes primarily from the knee, especially for his right leg. Now, I think that for him the reason for doing this is related to his arm action (more to that later), but it still illustrates how this exaggerated kick makes his legs move out of the wake of his body and thus increases his resistance. This might also be one of the reasons why Matt likes swimming with the pull buoy over kicking, it keeps his legs within the wake of his body decreasing the resistance the legs otherwise might present.
I generally tell my swimming students to kick out of the hips keeping the knees and ankles straight but relaxed, similar to kicking a ball with the instep. Think about small, fast kicks, not big, strong kicks.
2. Plantar flexed feet (Pointing Your Toes) and Ankle Flexibility
Plantar flexion is technical jargon for pointing your toes. When you swim you should always have your toes pointed, this presents a much lower profile to the water. Not pointing your toes will push water forwards when you kick, slowing you dramatically. (Swim Smooth, 2009)
Many triathletes have poor ankle flexibility limiting how much they can point their toes. In an ideal world you want to be able to flex your feet beyond straight.
If you have a background in cycling or running (especially running) then you’re likely to have stiff ankles such that you can’t achieve a straight foot. This will be hurting your kick technique and slowing you down when you swim. (Swim Smooth, 2009)
Ankle flexibility is an issue for most triathletes. And while improving ankle flexibility might be helpful, triathletes do not want to be as flexible as swimmers because that might increase their changes of injury, especially during running. Do you really want to have ankles that are as floppy as in this clip (http://youtu.be/akuxFXdhPEo)?
I also think that of all the things we can improve, ankle flexibility is probably the last one to consider. That said it probably would not hurt most of us to increase our ankle flexibility.
Here is some of what Swim Smooth (2009) has to say about timing:
The timing of the kick is something that we don’t normally think about much as swimmers. We have a variety of kicking speeds open to us as we’ll describe below – 2, 4 or 6 beats. The key to good timing is that when the hand enters the water at the front of the stroke, the opposite leg should kick. In 2 beat kick this is the only kick, in 4 and 6 beats there are other kicks in between but the kick on opposite hand entry is the important one for timing.
If your timing is wrong you won’t be helping your body rotation with your kick – you could even be counteracting it. …
Most swimmers kick with the correct timing naturally, unless you know you have a problem don’t be too concerned about timing – focus instead on pointing your toes and kicking from the hip, this is much more likely to be holding you back.
While I agree with what they have to say here, I think there are a few important points they do not address. I discovered some of these issues while doing some research on front crawl swimming at The University of Iowa (Kippenhan & Hay, 1994; Kippenhan & Yanai, 1995).
1. While most swimmers tend to do the timing naturally correctly, those who do not tend to find it difficult to incorporate the breathing into their stroke and tend to have problems with a good body roll.
2. Timing problems are often related to flaws in the arm stroke, i.e. weird stuff that happens with the kick is often caused by problems with the arm action. This actually can be explained with Newton’s Third Law, the Law of Action and Reaction. No worries I will not give you a lesson in mechanics here, but I want to point out some of this with the help of David’s clip as well as clips by two really good swimmers: Karlyn Pipes-Neilsen and Sun Yang
Sun Yang: http://youtu.be/uncOBURz-6o
You also can use any of the clips from the London finals listed earlier.
Look at David’s arm recovery from the front (above water). You might be able to see that he swings his arms from the outside in. This causes especially the left hand to enter in front of his head and move toward and sometimes crossing over the midline of the body. Now look at the expert swimmers, their hands tend to enter in extension of their shoulders and never move toward the midline of the body. David’s action introduces a snakelike movement of the body and he has to use the exaggerated kick (pointed out earlier) to counteract the movement.
Now look at David’s arm entry and catch from the front (under water). He enters the water, barely extends his arm forward (his elbows never straighten out), his hand and forearm push down against the water right away and start pulling. I call this “rushing the catch”. As a consequence the pulling arm is almost done with the underwater pull when the recovery arm enters the water. You might have to look at the clip several times to see all of this. Now look at the expert swimmers. They enter the hand in extension of their shoulder, and stretch it forward in a streamline fashion without pushing down on the water. This allows for several things, including an effective body roll, putting the pulling arm in a better position to finish up the push, facilitating a relaxed arm recovery and breathing action, and a more effective high elbow catch. It also helps with effective front quadrant timing, i.e. the pulling arm is still in the early part of the underwater pull when the recovery arm enters the water. With regard to the kick, based on my own experience, this timing of the arms makes it easier to properly time the kick with the arms. By stretching the arm forward, you allow the opposite leg to finish its kick before you start to pull (as described by Swim Smooth, 2009). If you ‘rush the catch,’ the downward kick of the opposite leg is not done yet when you start pulling, and kick and pull work against each other. BTW, this might be another reason why Matt likes swimming with a pull buoy, pull and kick can never work against each other since you do not kick.
Note, some of the issues described here, like outside in entry of the hand, or not reaching full extension in elbow and shoulders after entry, can be caused by a lack of shoulder flexibility. Based on my experience, while you do not need exceptional shoulder flexibility to be a descent swimmer, your upper arms should be able to touch your ears when you extend them above your head (e.g. when streamlining your body). And if I would have to pick between working on ankle flexibility and working on shoulder flexibility, I would go for shoulder flexibility.
(Picture Source: http://lead2tri.blogspot.com/2011/10/call-suit-evening-swim-clinic-with.html ) (Photo Link)
Kippenhan, B.C. & Hay, J.G. (1994). Body Roll and Breathing Action in Skilled and Unskilled Front Crawl Swimmers. In R.J. Gregor & A.S. Lisky (Eds.), Proceedings of the 18th Annual Meeting of the American Society of Biomechanics, October 13-15, 1994 (pp. 85-86). Columbus, OH, The Ohio State University.
Kippenhan, B.S. Yanai, T. (1995). Limb Motion and Body Roll in Skilled and Unskilled Front Crawl Swimmers. Medicine & Science in Sports & Exercise 27(5) (Suppl.), S232.
Maglischo, E. W. (2003). Swimming Fastest. Champaign, IL: Human Kinetics
Newsom, P. & Young, A. (2012). Swim Smooth. West Sussex, United Kingdom: John Wiley & Sons
Swim Smooth (2009). Leg Kick in the Freestyle Stroke. Retrieved from http://www.swimsmooth.com/kick.html