Whether it is catching or riding a wave into the shore on a coastal ocean swim or off the wall in a pool in a competitive pool meet, streamlining on your side is a topic for consideration.
It seems to give highly competitive swimmers a boost over their competitors, both in the open water into an onshore finish and in the pool off the walls.”
Ky Hurst of Australia, one of the world’s greatest watermen, is an example of a top open water swimmer who advocates this side-dolphining style.
“Dolphining on one’s side does seem slightly faster than traditional dolphining on one’s stomach, but it has to be practiced before implementing in a competition.
Competitive pool swimmers and their coaches know that, for most swimmers, kicking underwater on their back is faster than kicking underwater on their stomachs. And that kicking on their sides is even faster than both.”
There are various reasons why kicking on one’s back underwater or sides is faster than kicking on the stomach.
“The first reason is that water is non-compressible.
That is, your stronger muscles (i.e., your quadriceps) are pushing upwards when you are on your back – and your weaker muscles (i.e., your hamstrings) are pushing downwards when you are on your stomach. It is natural and assumed that your stronger muscles push more water (i.e., quadriceps versus hamstrings), but because water is non-compressible, the actual displacement of water is less where there is more water (i.e., kicking on your stomach where there is more water below you than above you) – and more displacement of water where there is less water (i.e., kicking on your back where there is less more above you than below you).
In other words, on your upkick when you are on your back and there is less water above you, more water is displaced compared to your downkick when you are on your stomach and there is more water below you – and therefore, there is less water displacement. The more water you displaces per square inch of area, generally the faster your propulsion all things being equal.
The second reason is a bit more subtle, but gravity has another effect that causes underwater kicking on your back to be faster than on your stomach. That is, your stronger muscles (i.e., your quadriceps) are pushing against gravity when you are on your back – and your weaker muscles (i.e., your hamstrings) are pushing with gravity when you are on your back.
The reverse is also true. That is, your stronger muscles (i.e., your quadriceps) are pushing with gravity when you are on your stomach and your weaker muscles (i.e., your hamstrings) are pushing against gravity when you are on your stomach. This leads to a slight difference in the amount of water that is displaced – and therefore, your speed is faster on your back.
Take those two principles (i.e., the non-compressibility of water and the effects of gravity) and their effects (i.e., a lesser or greater displacement of water) and then consider kicking on your side (i.e., fishlike kicking) in a pool. In a pool, there is more displacement on your side, due to the amount of water between yourself and the sides of the pool and due to a lesser effect of gravity…essentially, kicking on your side is most certainly faster than kicking on your stomach and faster than kicking on your back.
It also may be that the proper alignment of your head position and streamlined position of your outstretched arms are more easily accomplished on your back or on your side.”
Photo above shows Ky Hurst, courtesy of his website.
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