Mechanical Energetics of World Class Cross-Country Skiing

Abstract

The purpose of this study was to determine whether world class skiers were alike in their mechanical power outputs (normalized for body mass and velocity and called mechanical cost, MTC) and body segment energy transfers when skiing in competition on level and uphill terrain using the diagonal technique. Eleven competitors were analyzed from film taken during a 15-km World Championship race on a level (1.6°) and uphill (9.0°) section of the course. Metabolic rates were estimated from assumptions concerning the efficiencies of positive and negative work and calculations, from the film, of the mechanical power produced by the skiers. The results showed that skiing on the slope was 2.2 times more demanding mechanically than skiing on a level track (MTC of 4.0 vs. 1.8 J • kg −1 • m −1 , respectively). Skiers who had high MTC had low energy transfers (r = −0.9). Even in this presumably homogeneous group of elite skiers there were large individual differences in MTC and other mechanical variables, suggesting technique problems for some. Furthermore, on flat terrain the estimated metabolic rate was only about 76% of an MV0 2 of 80 ml • kg −1 • min −1 . This suggests that speed, using the diagonal stride, may be limited by constraints on body segment utilization and not by the physiological energy delivery system of these highly trained athletes.