Courtesy of Gary Hall Sr., 10-time World Record Holder, 3-time Olympian, 1976 Olympic Games US Flagbearer and The Race Club co-founder.
Have you ever noticed that leaner men or women often swim faster than bigger, stronger men or women? Reducing frontal drag is certainly one of the reasons why a leaner body may have the potential to swim faster, but there is another reason, called coupling motions.
Coupling Motion
A coupling motion is defined as kinetic energy created within the body that augments the effect of the propulsive forces. These motions can occur either at the same time the propulsive forces are acting, or while the effect of the propulsive forces are still occurring. In swimming, the propulsive forces are nearly all derived from the hands and the feet, as those (along with the forearm) are the only parts that actually move backward in the water as the body moves forward. Yet there are many other motions of the body that can be used to enhance those propulsive forces.
Visualizing An Example
Perhaps the easiest way to comprehend the effect of coupling motions is by visualizing a great relay takeoff. As the swimmer in the water approaches the wall, the swimmer on the block will step forward, first with one foot, then with the other. This sets the body in motion toward the desired goal of jumping as far out over the water as possible, taking advantage of the law of inertia. This motion is similar to the result that a long jumper running down the runway will have compared to a standing long jumper.
The swimmer on the relay also will swing the arms fully extended in a backward circle as fast as he or she can while pushing off the block with the feet. The kinetic energy of the arm swing is increased by lengthening the arms maximally (radius) and by swinging the arms as fast as possible (angular velocity). The act of swinging the arms does not lead to any direct propulsive forces that help the swimmer get off the block, but when coupled with the force of the legs pushing the swimmer, that motion results in a longer jump. The parts of the body are not working as an isolated system, but rather connected together in an open system, where all the motions of one part affect, either positively or negatively, the propulsive forces created by another. Further, all motions are also affected by outside forces in this open system, such as gravity and frontal drag, which impact our swimming speed.
There are other less important coupling motions that occur on the relay start, such as lifting the head forward during the jump and kicking the back leg up in the air, but the net result of all of these coupling motions acting during the time the force of the push off the block is still taking place, result in a better relay take off. Coupling motions not only occur in swimming, but in virtually every sport. The long jumper continues to move his legs and arms while in the air. The golfer or baseball player rotates the body and swings the hips forward to get a longer drive or a hit the ball more powerfully.
Coupling Motions Differ For Each Stroke
The coupling motions of a swimmer differ for each of the four strokes. In freestyle and backstroke, for example, the rotation of the body and the recovering arm swinging over the top of the water during an underwater pull can augment the distance a swimmer travels from the force of each pull (DPS). The faster the body is rotating and the longer and faster the arm is recovering, the greater the effect of the coupling motion. In breaststroke and butterfly, most of the coupling motions occur during the kick, not the pull. In breaststroke, the lunge forward of the upper body and head, timed precisely with the backward kicking motion, results in a longer glide after the kick. In butterfly, the swing of straight arms over the top of the water and the snap down of the head are coupled with the second down kick, resulting in more distance traveled from that kick.
Why Doesn’t Everyone Do Them?
If coupling motions really make us swim faster, why doesn’t everyone do them? The reason is that they require work, over and over again. It is much easier to swim by minimizing the energy in these coupling motions, but we swim much slower. In order to swim fast, we need to put a lot of energy into the effort, but it must be spent intelligently. Motions that do not couple with our propulsive forces or that lead to a huge increase in frontal drag will simply wear us down.
Gary Hall, Sr., Technical Director and Head Coach of The Race Club (courtesy of TRC)
No one said swimming fast was easy, but one must also swim smart by using coupling motions. Read more about the Science of Coupling here: http://www.theraceclub.com/aqua-notes/freestyle-recovery/
Yours in swimming,
Gary Hall Sr.
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I think I understand how coupling motions make one faster, but I’m not clear on what the coupling motions have to do with being lean. Are you saying that leaner people find coupling motions easier, or that they are leaner because they utilize coupling motions? Or, are you just trying to say that being lean reduces frontal drag and so do coupling motions? When I swim freestyle I feel like my hip and shoulders are connected in a way because they move together.
You are on the right track. I would not use the word recycle, but both the recovering arm and the rotation of the body, occurring at the the time of the force of the underwater pull is created, both augment the effect of the pulling arm, getting you further down the pool. We are calling these motions coupling motions (since the body parts are all connected). The more the kinetic energy of the coupling motion, the more the impact has on the propulsive force(s).
Gary thanks for the wealth of knowledge here. Love TRC.
I *think* I might understand this, but wonder if you would be gracious enough to analyze my line of thinking here. With my hip driven stroke I don’t feel like I have nearly as much of this coupling action going on. With my shoulder driven stroke I definitely feel the linkage across the top of my shoulders almost like a T if you will. The weight and momentum of my recovering arm ‘recycles’ some energy to propel my catching/pulling arm.
Is this what you are describing? Or did I completely miss the proverbial boat? Thanks for your input.
You are likely correct. With the slower hip-driven freestyle technique, the arm recovery and body rotation are usually slower than with the faster stroke rate of shoulder-driven technique. One can increase the coupling energy of a slower stroke rate by making the last 1/4 of the recovery very hard. This not only increases the energy of the arm, but also forces the body into a quick rotation at the same time (which is the critical time). Popov’s technique was great at this; low octane (bent elbow) recovery…yet with a force throw down of the hand at the end and quick body rotation. Made him pretty fast!
Gary:
You may find these videos interesting. Image them upside down with the throwing arm pushing back on the water and the counterweight being your shoulder. Could explain that the acceleration we see at the end of the Free and Fly pull comes from kinetic energy instead of trying to push your hand back.
http://www.pbslearningmedia.org/resource/hew06.sci.phys.maf.trebuchet/energy-transfer-in-a-trebuchet/
Don’t play the game in this one.
http://www.real-world-physics-problems.com/catapult-physics.html
If you watch the Netflix series Marco Polo, in the final episode you will see that same device he helped design used so the Mongols could break down the walls of China. Must be something to it! I wonder if we will ever see swimmers wearing lead rings around their fingers?
Where do I find these camps? This is a very interesting article. I’m a swimming getting ready to swim in college next year and I am really working hard on improving my speed.
HI Samantha, You can come to The Race Club anytime. We have camps in CA and in FL. Our camps are unlike any other camp, so email for more information. Here’s the link to our camps and private session page: http://www.theraceclub.com/swim-camps/ and my email is [email protected] Thanks!
I recommend spending some time with Gary, no mater what level you are on.