Courtesy of Gary Hall Sr., 10-time World Record Holder, 3-time Olympian, 1976 Olympic Games US Flagbearer and The Race Club co-founder.
Propulsive Forces & Frontal Drag Forces
Sir Isaac Newton’s three laws of motion are as applicable today to a swimmer as they were centuries ago when he formulated them. However, for me it is easier to conceptualize the application of the three laws by separately considering the forces that move us through the water (propulsive forces), the forces that slow us down (frontal drag forces) and the law of inertia, which tells us it is most efficient to maintain a constant speed by keeping the forces of propulsion and drag equal.
The propulsion of a swimmer is derived primarily from two sources, the hands and the feet. However, there is another motion involved in the freestyle and backstroke of a fast swimmer, other than kicking and pulling, that is vitally important to generate more propulsion; the axial rotation of the body from side to side.
Freestyle & Backstroke
Although coaches and swimmers commonly believe that one of the reasons fast freestlyers and backstrokers rotate their bodies along the axis of their motion is to reduce drag, I don’t agree. If that were true, we would see a substantially faster kicking speed on our sides than we do on our stomachs or backs, and that is simply not the case.
Another common theory for why we rotate our bodies in freestyle and backstroke is so we can reach out further on each stroke. While that may be true at the finish of a race (particularly freestyle), I don’t believe the extension of the arms on the recovery of a rotating swimmer is any further than on a non-rotating swimmer.
Mechanical & Biomechanical
There are two reasons for rotating the body during freestyle and backstroke. One is mechanical and the other is biomechanical. The biomechanical reason is that by rotating our body to initiate the underwater pull, we put ourselves into a more favorable position to use our back muscles, particularly the large latissimus dorsi muscle. That will make our pull stronger.
The mechanical reason is that by counter-rotating our bodies during the underwater pull we can create a significant force to pull against. In other words, we are no longer pulling against just water molecules that are relatively motionless. We now have the water, plus whatever force we can generate with the counter-rotation of our body. The amount of that force that we get to pull against is related to our mass (weight) and to the angular velocity of our body’s rotation (how fast we rotate).
The rotation of the body doesn’t just happen. A swimmer has to make it happen and that requires a lot of core strength and work. When the rotation is fast and timed well, it is worth the effort, creating a substantial force that enable the swimmer to cover more distance with each stroke.
No one said swimming fast was easy. Here are some of our favorite drills:
Yours in Swimming,
Gary Hall Sr.
[email protected] <http://[email protected]
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