Brent S. Rushall, Ph.D., R.Psy.


Manufacturers advertise that bodysuits enhance the performance of competitive swimmers. That claim has yet to be verified in a public forum. Manufacturers cite their own "research" as supportive evidence, but independent scrutiny of those claims has not been forthcoming. As much as can be gleaned from snippets of information, it is suggested that their privileged research has been based on incomplete and inappropriate theory, tested in inappropriate settings (e.g., a swimming flume), and falsely externally validated. Support for bodysuits has largely come from swimmers and coaches paid by manufacturers.

In practice, it seems that bodysuits do not live up to manufacturers' theoretical claims of benefit.

However, there can be no doubt that some swimmers do benefit from wearing bodysuits, at least those that extend from neck to knee. It is proposed that the benefit is caused by a mechanical effect that was not contemplated by the manufacturers or their scientific theorists. Only some swimmers enjoy this benefit.

Some swimmers have a technique flaw that causes excessive hip sway back and forth in crawl and backstroke, or rise and fall in butterfly. Excessive hip movements usually result from faulty stroke entries. These movements cause an increase in active drag, mainly from two sources: i) increased form resistance, and ii) increased wave resistance. The increased resistance requires extra energy to create force to propel a swimmer at a certain speed.

Bodysuits fit very tightly. That tightness has been found to restrict movements around the shoulders and arms in all strokes, and around the knees in backstroke and breaststroke. However, in other parts of the body restriction can be beneficial.

The tightness of bodysuits, at least from neck to knee, restricts the amount of excessive hip sway. The reduction in movement range also reduces the two forms of detrimental resistance, resulting in more efficient propulsion (i.e., faster swimming for the same amount of energy expenditure).

For a swimmer to outwardly benefit from wearing a bodysuit, there first has to be the technique flaw. Second, the suit has to be tight enough to restrict hip sway. Third, the swimmer has to be convinced of the improvement caused by this physical action.

In this restrictive mode, a bodysuit is a true device that enhances performance/speed.

There is support for this proposal. Three of the four world butterfly records that have been set in the past two years have been in neck-to-knee or neck-to-ankle bodysuits (Inge de Bruin, Tom Malchow, Susan O'Neill). Michael Klim's 100-m butterfly record was set using a waist-to-ankle suit, after he discarded a neck-to-ankle suit. Most modern butterfliers, and in particular Klim, Malchow, and O'Neill displayed excessive vertical hip movements when wearing normal swim suits. The restrictiveness of the bodysuits should be of benefit to their stroking efficiency.

Female swimmers are forced to wear a torso covering and therefore, should enjoy the mechanical benefit of "tight" bodysuits that force improved, or maintain beneficial streamlining from the torso through to the knees. The controversial and top female swimmers of today wear these suits. They are not quite as popular among men.

The suits have an added ergogenic effect. When they mechanically hold the hips, torso, and thighs in good alignment, a swimmer expends less muscular energy to maintain a streamlined posture. The energy freed from such a task can then be used to generate propulsion. Performances are enhanced by the added source of energy.

These mechanical effects are unlikely to be enjoyed by all swimmers. But, if the conditions are right, the suits are true devices that alter the kinetic function of the swimmer.

Following this precedent set by FINA's approving these suits, it should now be possible to wear restrictive devices that limit the range of movements of joints to those that yield the most efficient force generation, or limit the production of detrimental drag resistance.

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