Energetic Considerations in Cross-Country Skiing

Abstract

Crosscountry skiing is a four-legged gait, and some gait patterns, such as 2-skate skiing, are similar to those adopted by animals (galloping horse). Four-legged animals change gait patterns with increasing speeds of locomotion, at least in part, to minimize metabolic energy expenditure. For example, a horse will switch from a walk, to a trot, and finally to a gallop as speed of locomotion increases. Similarly, skate crosscountry skiers will switch from a 2-skate gait to a 1-skate gait with increasing speeds of locomotion, but then unlike any other animal, will revert back to the previously rejected 2-skate gait pattern at very high speeds. We used oxygen uptake measurements, force measurements in poles and skis, 3-dimensional movement analysis and functional muscle properties to explain this result. We found that propulsion in 1-skate skiing comes primarily from the arms/poles, while propulsion comes primarily from the legs/skis in the 2-skate technique. We also found that ground contact times for the skis are virtually independent of the skiing speed while pole contact times decrease dramatically with increasing speeds. Furthermore, propulsive forces from the arms dropped from skiing at 15 km/h to skiing at 30 km/h while simultaneously requiring much more metabolic energy. Finally, the cost of transport curves for 1-skate and 2-skate skiing intersected twice, indicating better efficiency for the 2-skate technique at slow and very fast speeds, and better efficiency for the 1-skate technique at intermediate to fast speeds. Combined, these results suggest that arm/pole action is optimized at intermediate speeds, thereby providing an advantage to the 1-skate technique which relies primarily on arm propulsion, while arm/pole action is highly inefficient at very high speeds, thus switching to the 2-skate technique which relies primarily on leg propulsion, is good strategy.

Temporal and kinematic patterns distinguishing the G2 from the G4 skating sub-technique

“…One main similarity between these two sub-techniques is that of one double poling movement on every second ski push. Based on that, Herzog et al (2015) considered G2 and G4 to be the same unique sub-technique. However, in the present study, we find large differences in both forward, lateral and vertical movement of the CoM throughout the skiing cycle.…”

“…Recently, Herzog et al (2015) showed that these transitions between sub-techniques indeed occur. However, since both G2 and G4 have only one pole push for every second leg/ski push, they characterised both G2 and G4 as the same sub-technique, labelled 2-skate.…”