In competitive swimmers, the wake generated by the leading swimmer induces significant reductions in energy cost (from a mean value of 3.12 [+ or -] 0.66 to 2.85 [+ or -] 0.63 l x [O.sub.2] x [min.sup.-1]), in blood lactate concentration (from a mean value of 5.0 [+ or -] 0.5 to 3.4 [+ or -] 0.6 [mmol x l.sup.-1]) and in perceived exertion ratings (from a mean value of 14.9 [+ or -] 0.5 to 11.7 [+ or -] 0.4) in the back swimmer (Bassett et al., 1991).
This distance was measured from the toe tips of the leading swimmer to the head vertex of the back swimmer. The position of the leading swimmer remained constant during all simulations.
To estimate the Cd of the back swimmer and compare it with the assumed Cd of the leading swimmer, a curve fitting based on the application of various polynomials was performed.
The lower pressure zones coincided with the flow around the back swimmer. The inherent conditions in the leading swimmer were different from the conditions verified in the back swimmer (see Figure 3).
However, it was possible to verify that for all the velocities and distances higher than 6 m (until 8 m), the back swimmer's Cd remained almost constant and did not tend to the value presented by the leading swimmer.
The results indicated that the Cd of the back swimmer (considering the various flow velocities) was equal to that by the leading swimmer in distances ranging between 6.45 m and 8.90 m (see Table 1).