Coaches' Corner

Butterfly stroke timing

The following video shows two swimmers performing the butterfly stroke with different timings of the second kick.  We will refer to the kick that occurs as the hands enter the water as the first kick, the kick that is generally timed as the hands exit the water as the second kick.  You should be able to see that the swimmer in the bottom half of the screen performs the second kick earlier, the legs finish the downbeat of the second kick while his hands are still midway through the pull.  Here's the view from above water:

  The timing can be observed more clearly in underwater video of the same swims:

Here is a still shot at the point where the bottom swimmer has completed the downbeat of the second kick:

Note that the arms are only midway through the pull.

For comparison, here is a shot where the top swimmer has finished the downbeat of his second kick:

Note that his hands are just leaving the water.

Finally, here is a shot of Michael Phelps at the same point in his stroke:

His hands can just be seen passing his swim suit on their way to leaving the water.

There are a few reasons to prefer the hand exit timing.

The top swimmer pauses his kick for approximately the middle third of his pull when his legs have been recovered to the surface and he is in a relatively flat streamlined position, minimizing drag resistance.  In contrast, the pause in the bottom swimmer's kicking occurs in the last third of his pull when the legs are at maximum depth resulting in much more drag resistance.  Compare the body positions in the first still image above.

For the top swimmer the second kick is providing extra propulsion just as he is launching forward into the recovery, helping maintain the speed generated by the pull and making it easier to cleanly recover the arms.  The bottom swimmer gets the extra forward propulsion early in his pull which does increase his speed at that point but then he loses considerable speed during the recovery and has to expend extra energy in the finish of the pull and the recovery of the arms.

The downward force on the water generated by the downbeat of the top swimmer's second kick should also help maintain a flatter position during arm recovery.

The bottom swimmer would likely benefit from reducing the amplitude and vigor of his vertical movements, and avoiding lifting his lower legs clear of the water, but these elements may result from attempting to compensate for dynamics caused by the timing of the kicks and may go away on their own if the timing is adjusted.

Posted at 10:59PM Jan 29, 2010 by Lindsay in General  |  Comments[0]