Effects of drafting on energy expenditure in in-line skating.

AIM The purpose of this study was to measure the effects of drafting on energy expenditure in in-line skating, and to investigate whether the "benefit of drafting", i.e. the decrease in energy expenditure, was different between two velocities and two distances separating the two skaters. METHODS Eight recreational in-line skaters performed six exercises of 6 min, at 2 velocities (V(1) = 5.51+/-0.45 m x sec(-1); V(2) = 7.01+/-0.67 m x sec(-1)) in 3 conditions (ND = without drafting; D(1)=0.74-0.87 m "close"; D(2) = 1.19-1.36 m "far"). Collection of expired gas was carried out using a breath-by-breath portable gas analyser K4(b2) and the distance between the skaters was measured by video analysis. RESULTS The skaters' energy expenditure was reduced in all drafting conditions; between D(1) and ND by 9.6+/-4.4% at V(1) and by 2.7+/-3.3% at V(2); between D(2) and ND by 8.8+/-6.0% at V(1) and by 4.2+/-4.8% at V(2). This reduction was significantly (p<0.05) more important at V(1) than V(2) and no differences were observed between D(1) and D(2). CONCLUSION In in-line skating, the technical difficulties for drafting efficiently, especially while cornering, resulted in a reduced "benefit of drafting" at high velocity than in other sports. Moreover, the need for the subject to adjust their own cycle frequency to that of the lead skater while drafting "close" would explain partly that there were no significant differences between drafting at D(1) and D(2). These results suggest that the drafting technique should be emphasized in training, especially in non-skilled skaters at high velocities and when cornering.