Triathletes, draft in water.

A new study suggests that drafting off of an opponent during the swimming leg of a triathlon can improve your cycling leg. Researchers at the National Institute of Sport and Physical Education in France found that swimming directly behind a competitor improves your biomechanical adaptation during the subsequent cycling portion of the race. While drafting during running, biking, and even cross-country skiing has long been common practice--even to the point where it is expected that Olympic competitors will share the lead--the practice is less common among swimmers.

A group of male triathletes underwent separate sessions involving a 10-minute bike ride at 75% VO2max, either preceded by a 750-meter swim alone, or a swim in drafting position at the same pace. The decrease in energy expenditure (sometimes referred to as "metabolic load") found during the drafting swim caused a significantly lower pedal rate with higher torque as compared to the swim-alone sessions. Fatigue manifested later in the lower limb muscles of the cyclists who drafted during the swimming portion of the trial, as measured both by biomechanical analysis and perceived exertion in the cyclists.

Not only did the drafting-swim cyclists improve their cycling efficiency, but they actually modified their locomotor pattern. These subjects enjoyed a lower pedal rate in their biking portions. In cycling events, the biomechanical factor most often cited in the literature to account for increases in metabolic load is pedal rate. The researchers cite a concept known as energetically optimal cadence (EOC), and note that the cadence obtained by the drafting-swim cyclists was in the range of the EOC found in previous cycling studies. As cadence drifts from EOC, as was the case in the swim-alone trials, studies consistently report a higher energy expenditure. Pedaling at a higher rate is associated with a decrease in the force produced by lower limb muscles during cycling.

(J. Applied Biomechanics, 2005, Vol. 21, No. 3, pp. 297-308; Can. J. Applied Phys., 2001, Vol. 26, pp. 44-54; Int'l J. Sports Med., 2000, Vol. 20, pp. 60-64)