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The Energy Systems of the Swimmer

By Gary Hall Sr. | Aug. 02, 2016, 6 a.m. (ET)

swim school

Go back to school! Erase the smelly, crowded hallways of your high school from your mind and imagine yourself under the Islamorada sun in a clear pool ready to absorb knowledge that will enable you to swim faster. Swim School from Gary Hall Sr. of The Race Club is about lifelong enjoyment of the sport. It’s always more fun to swim to your potential.

I often speak of the three fundamental laws that govern our swimming techniques, the forces that propel us, the forces that slow us down and the law of inertia. All are important, but because the motions involved in maximizing propulsion are different than the motions that minimize frontal drag forces, we find that swimming effectively involves a constant compromise between these two forces. The result of the compromise is that we cannot find one single best way of swimming fast for short or longer distances. Nonetheless, there are commonalities among all great swimmers.

swimmingAlthough the three laws above, which are really just Newton’s three laws of motion redesigned for the swimmer, are critical to stroke technique, there is yet another law that comes into play primarily on the recovery part of our strokes. That is the law of conservation of energy.

This law tells us that within an isolated system, energy cannot be created nor destroyed, but it can be transformed to other types of energy or transferred to other systems. A good example of this is when a car collides into a stationary vehicle. The energy of the moving car gets transferred to the stationary car and causes it to move. The stationary car will not move as fast as the moving car was originally going because some of the energy is transferred to heat, bending metal, etc.

One can consider that within a body, including head, arms and legs, swimming down the pool, there are several energy systems working at the same time. The body itself is one linear system, propelled by the hands and feet. There are also rotational energy systems, including the body rotating on the horizontal axis of motion and the legs rotating slightly and mainly from the hip. Since both of these rotating systems reverse directions often, the net effect is that neither transfers any appreciable amount of energy to the linear kinetic energy of the body. With the legs, this energy is not to be confused with the propulsive forces of the feet, which can potentially contribute much propulsive power (in good kickers). Without providing the high rotational energy of the legs, the feet would not have the speed to generate that force. The rotating body creates a counterforce to enhance the pulling motion, so it also serves an important purpose. What I am considering is the angular momentum of the entire leg or rotating body contributing to the linear energy of the body, which is nil.

However, if we consider the recovering arms and, depending on the stroke, the upper body and head as more rotational energy systems, the potential transfer of energy to the linear moving body from them can be significant. One of the reasons is that recovering parts of the body are moving in the forward direction. They are also moving through air, which enables the angular velocity to increase greatly. The total amount of energy in the angular system is the multiple of the angular velocity and the moment of inertia, which is determined by the mass and the length of the arm. In other words, we can increase the energy within the system of recovering arms by using a straight rather than bent arm and by moving the hand as quickly as possible through the recovery phase of the arm cycle.
Once the hand (or head or upper body) hit the water, a collision of sorts takes place, just like the cars. At this point, the angular velocity goes to nearly zero and so the energy of the system must transfer somewhere, and it does. Part of it goes toward the splash or disruption of water molecules and the remainder, through the connection of ligaments, tendons and muscles attaching the arm to the body, toward the body moving forward.

It is for this reason that the straight-arm recovery moving very quickly has the potential to transfer more energy and help increase the speed of the swimmer than the bent arm recovery does. It also requires more work of the swimmer to create this higher energy system. It is also for this reason that in butterfly, the head should be snapped down, not laid down slowly, and in breaststroke, the upper body should snap forward and down, not lowered slowly into the water. All three of these motions, fast straight-arm recovery, snapping the head down in fly and snapping the upper body down in breaststroke, have the potential to make a swimmer go faster.

No one ever said swimming fast was easy. To swim fast, one must also swim smart.

Yours in swimming,
Gary Hall Sr.

gary hall srGary Hall Sr., M.D. is a three-time Olympic swimmer (‘68, ‘72, ‘76) who earned a medal in each of the three Olympic Games. At one time he held 10 world records in all strokes except breaststroke and was the World Swimmer of the year in 1969 and 1970.

Gary Sr. serves as president and technical director of The Race Club Inc. based in Islamorada, Florida. He is the current president of the United States Olympians and Paralympians Association and co-founder of World Fit, a non-profit organization promoting childhood exercise and sports. He has six children, the oldest of whom, Gary Jr., also swam in three Olympic Games (‘96, ‘00, ‘04) and earned 10 Olympic medals. Two other children, Richard and Amy, and his wife, Mary, work with Gary Sr. at The Race Club. In 2006, Gary Sr. retired from ophthalmology to dedicate his remaining professional career to teaching advanced swimming techniques for competitive swimmers and triathletes. 

The views expressed in this article are the opinion of the author and not necessarily the practices of USA Triathlon. Before starting any new diet or exercise program, you should check with your physician and/or coach.