Butterfly Technique: Holding Your Speed in Butterfly
After breaststroke, butterfly is the next most inefficient stroke. That is the main reason butterfly is so hard to do. In butterfly, the swimmer’s speed tends to vary quite a bit, which does not take advantage of the law of inertia. However, there are some excellent techniques that great butterflyers use to help hold their speed, increasing their efficiency.
We have written about the five most common break points in butterfly, which cause excessive loss of speed: Overbending knees on the kicks, over flexing (undulation) of the hip, over elevating the shoulders on the breath stroke, allowing the feet to hang too long after the down kicks and the wide arm entry. One can measure these key angles by using a virtual protractor with an underwater side view of the butterfly swimmer.
There are two peak velocities that occur in each butterfly cycle, called PV1 and PV2. One can also get a sense of a broken butterfly stroke by measuring the percentage of loss of velocity after each of the two peak velocities per cycle.
PV1 and PV2 correspond to the two down kicks of the butterfly cycle. The intensity, mechanics and propulsion derived from the two down kicks are quite variable among swimmers; not just from swimmer to swimmer, but also from the first kick (K1), which occurs during the swimmer’s pull, and the second kick (K2), which occurs as the swimmer’s arms/hands enter the water.
Among elite butterfliers using two strong down kicks, we often see PV1 and PV2 nearly equal. That may seem surprising, since PV1 is reached from the propulsion of a kick and a pull and PV2 is reached from the propulsion of a kick only. With strong and well-timed coupling motions from the arms and upper body, and a better drag position after PV2 than PV1, the two peak velocities can and should be similar.
The time that elapses between PV1 and PV2 is less than the time that elapses between PV2 and the following PV1. With that longer time between PV2 and the next PV1, one might think that more velocity would be lost during that period. However, after PV2, the ensuing pull helps sustain the swimmer’s velocity. More speed is usually lost after PV1, when the arms are recovering, than after PV2.
The percentage loss of velocity after each peak velocity (PV1 and PV2), which we now measure using our new TRC App, hinges on several important techniques, including the five break points described above:
Techniques to hold your speed after PV1
1) Create a low body angle. The body angle is largely determined by the height of the shoulder elevation during the breath and by the flexibility of the shoulders during the recovery.
2) Point your toes earlier after K1. Allowing the feet to hang too long after a hard K1 down kick can add significantly more drag.
3) Use a strong up kick after K1. The up kick after K1 is often very weak. If worked hard, it has the potential to add propulsion and help hold your speed.
4) Avoid overbending the knees before K2. How far and how aggressively the legs are drawn forward for the next down kick (K2) can significantly impact the drag forces.
5) Increase your tempo. Getting the recovering arms back into the water quickly and into the propulsion phase lessens the time for the swimmer’s speed to drop.
After the first down kick, this swimmer reaches a peak velocity of 2.85 m/sec, but his body angle of 26 degrees is too steep.
It is appropriate to follow through with the feet on the down kick, but one cannot leave them hanging too long without causing more loss of speed.
After K1, the following up kick is the only propulsion available until the next pull starts. Working the up kick will help hold your speed.
One of the most significant causes of losing speed is how aggressively and how far the knees are bent before next down kick. The peak drag force occurs as the legs are drawing forward, not at maximum knee bend.
What often separates the fast swimmers from the not-so-fast swimmers is not the amount of propulsion generated, although that can be significant. Rather, it is the ability of the fast swimmers to hold their speed better while swimming, causing less drag and taking advantage of inertia, that makes the biggest difference.
Next week, we will discuss the techniques required to hold your speed better after PV2.
Yours in Swimming,
Gary Sr