When swimmers dive into the water, they battle more than nerves, physical exhaustion, and (perhaps) other competitors- they battle the laws of physics. These laws- some of which are unique to an aqueous environment- have long challenged scientists and engineers to devise methods to surmount them in order to successfully increase swimming speed. The end result of their exhaustive research (thus far), however, has rejected such a concept as "surmounting" the laws of physics. But they have shown that these laws can be manipulated to significant effect-if one understands the 'physics of swimming'.
Physics of Swimming
It may be a cruel joke of nature, but the biggest restriction to a swimmer's speed is the water in which he or she swims. Water is approximately 1,000 times denser than air and, as such, quickly (and sometimes severely) hinders movement. This effect is known as "drag," and is particularly onerous to swimmers.
Drag. Scientifically speaking, drag is the resistant force on a moving body that is traveling through (in this case) water. The strength of the drag is predicated upon many factors such as speed of the moving body, the body's surface area, and the water density in which the body moves. Generally, the faster a body moves through a medium (whether air or water) the stronger the resistance (drag) to such movement.
Drag does not just affect swimmers. Rather, all moving objects-such as automobiles, airplanes, and bicyclists-are subject to the resistant forces of drag. However, the properties of a watery environment increase this effect significantly. Indeed, the effort to increase swimming speed in such an environment exposes a swimmer to not just one-but three-different forces of drag.
Three Forces of Drag
The three main forces of drag that affect swimmers include friction, pressure, and wave drag. Each of these forces negatively impacts the swimmer's speed.
Frictional drag is caused by the swimmer's body continually rubbing against water molecules. This friction slows the forward momentum of a swimmer (and is also the force felt while wading knee-deep in the ocean). That said, frictional drag is also considered to be beneficial to a swimmer, in that it serves to propel the swimmer forward.
Pressure drag is caused by the increased speed of a swimmer. As the swimming speed increases, water builds up around the head, causing a pressure differential between the two ends of the swimmer's body. This differential creates a force that increases proportionally with the effort to increase swimming speed, further hampering forward momentum.
Wave drag is created when, at racing speeds, the swimmer creates an increase of pressure around the body, causing waves. These waves further try to slow the swimmer's speed and, as with other forms of drag, this resistance intensifies in correlation to the swimmer's speed.
Manipulating Drag to Increase Swimming Speed
Research into the mechanics of drag have led to some fascinating, and effective, methods for counteracting these effects and hence increasing the swimmer's swimming speed.
It's in the Hips
In 1984, Bill Boomer videotaped and intensively studied every swim stroke of every swimmer in the US Olympic trials. Boomer, a swim coach at the University of Rochester, was curious as to why many championship swimmers did not appear to be working very intensely (via the number of strokes) to win their races. What Boomer discovered transformed the sport of swimming-the fastest swimmers, he found, took the fewest strokes.
How is this possible? Boomer found that the length and the efficiency of each stroke determines the speed of a swimmer, and that such factors are greatly influenced by the amount, and power, of hip rotation. Powerful hip rotation radiates this power through the entirety of the body.
Hip rotation was not a new concept. Most championship swimmers had been swiveling their hips to Olympic gold, albeit unconsciously, for many years. But only recently have scientists verified the use of conscious hip rotation to increase swimming speed. Hip rotation, research has shown, creates a narrower profile in the water, which greatly reduces drag.
Experts recommend the following for those desiring to develop proper hip rotation while swimming: one should consciously swivel the navel toward the same side of the pool as the arm stroke. For instance, when the right arm enters the water, the right hip should point toward the bottom of the pool. The body should roll back and forth in the water in perfect rhythm to the strokes. To maximize the drag-reducing benefits of the hip rotation, experts suggest that the arm be fully extended at the start of each stroke.
Proper Body Positioning
Another key factor in minimizing drag lies in proper body positioning. To reduce drag, experts recommend that the body remain parallel to the water. The body should be extended and as straight possible. The head may be pointed down or to either side (as needed) but should never look forward. Looking forward causes the legs to point downward, which results in a loss of alignment and a resulting increase in drag. The head should be aimed in the direction of the intended destination.
Grab the Water
Too many swimmers, say experts, rely upon their hands alone to stroke the water. The proper way to reduce drag, and increase swimming speed, is to reach out and literally catch the water. This will transfer muscle power to the water much more effectively than will occur through use of the hands alone. Experts further recommend that a swimmer use the hands and the forearms as if to climb over a virtual wall, whereby the hands function as imaginary paddles and thus displacing a greater amount of water.
Swimmers have long experimented with different swimwear in the belief that aerodynamic benefits would be realized, .hence increasing swimming speed. To this end, they have historically donned swim caps and skin-tight swimsuits. Now, engineers are involved in designing suits using specific materials that studies have shown to contain properties inherently effective in reducing frictional drag and thus increasing swimming speed.
These are only a few of the recent techniques that have been developed in response to the scientific studies regarding the implications of drag on swimming speeds. It is likely that future research into the physics of swimming will yield more advances benefiting future generations.