The energy cost of level cross-country skiing and the effect of the friction of the ski

Summary

Oxygen consumption [($\dot V_{{\text{O}}_{\text{2}} }$) in ml·kg⁻¹·min⁻¹], blood lactate concentration ([La] in mM) and dynamic friction of the skis on snow [(F) inN] were measured in six athletes skiing on a level track at different speeds [(v) in m·min⁻¹] and using different methods of propulsion. The$\dot V_{{\text{O}}_{\text{2}} }$ increased withv andF, the latter depending mostly on snow temperature, as did [La]. The$\dot V_{{\text{O}}_{\text{2}} }$ was very much affected by the skiing technique. Multiple regression equations gave the following results: with diagonal stride (DS),$\dot V_{{\text{O}}_{\text{2}} }$ =−23.09+0.189v+0.62N; with double pole (DP),$\dot V_{{\text{O}}_{\text{2}} }$ =−30.95+0.192v+0.51N; and with the new skating technique (S),$\dot V_{{\text{O}}_{\text{2}} }$ =−32.63 +0.171+0.68N. In terms of$\dot V_{{\text{O}}_{\text{2}} }$ DS is the most expensive technique, while S is the least expensive; however, asF increases, S, at the highest speed, tends to cost as much as DP. At speeds from 18 to 22 km·h⁻¹, the speeds measured in the competitions, theF for DS and DP can represent from 10% to 50% of the energy expenditure, withF ranging from 10 to 60N; with S this range increases to 20%–70%. This seems to depend on the interface between the skis and the snow and on the different ways the poles are used.