Deschodt, V. J. (1999). Relative contribution of arms and legs in humans to propulsion in 25-m sprint front-crawl swimming. European Journal of Applied Physiology and Occupational Physiology, 80, 192-199.

Males (N = 8) swam 25 m at maximal velocity with the arms and legs alternately restricted. Four conditions of arm and leg movements were evaluated:

• one arm;
• two arms;
• one arm and two legs; and
• two arms and two legs.

An average increase in velocity of 10% occurred between the conditions using two legs and those using arms only.

The contribution of the leg kick in the 10% gain in maximal velocity was assessed. When kicking, the underwater trajectory of the wrist was modified in an improved manner. Therefore, it was thought that the contribution of the legs was that of enhancing the propulsive action of the arms rather than producing propulsive forces themselves. Inter-individual patterns of movement were particularly varied and could not be used to describe one particular common "style."

Implication: The kicking action in crawl stroke is not propulsive to any significant degree. Rather, it facilitates better arm actions, which in turn increase propulsion and improve velocity.

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