Using almost every muscle in the body and with a low risk of injury, cross-country skiing has a reputation for being one of the healthiest sports, but the pastime is not without challenges. Coordinating all four limbs on a slippery surface can have its moments, and athletes have to manoeuvre themselves up hills while gliding across the snow. But how do cross-country skiers propel themselves as they glissade up gradients? Are they effectively running as they glide on one ski while stepping forward with the other, do they store bouncy energy in the Achilles tendon of the sliding leg in preparation for the next stride, and how do the calf muscles contribute? To find out, Øyvind Gløersen (SINTEF Digital, Norway), Amelie Werkhausen and Anders Lundervold (both from the Norwegian School of Sport Sciences, Norway) filmed 13 competitive cross-country skiers on roller skis as they propelled themselves uphill on a sloping treadmill while recording calf muscle activity to find out how the skiers use energy while gliding along.

Recording the athletes manoeuvres with 12 cameras to reconstruct their movements as they roller skied on different inclines on the treadmill, the team saw the skiers kick off with one leg to swing it forward while gliding on the other, before touching down with the first leg to glide forward as the second leg kicked off, propelling the skier. Then, they analysed the complicated relationship between the calf muscle contraction and the Achilles tendon stretching to store energy as the skiers climbed and realised that the athletes’ movements were similar to those of runners. However, instead of bouncing into the air as they travelled forward, the skiers remained in contact with the treadmill, gliding forward on one ski. The researchers also realised that as the skiers prepared to push off with one leg, at the end of gliding on that ski, they contracted the calf muscles to store energy in the Achilles tendon, which is exactly what we do when preparing to jump. In addition, when the skiers propelled themselves up a steeper gradient, they contracted their calf muscles more to store a larger amount of energy in the Achilles tendon, to power the stronger kick they require.

So, cross-country skiers effectively run, but instead of bouncing into the air like runners, they glide forward across the snow, while benefiting from the power of jumping to ski up gradients that other skiers would be happier to descend.

Werkhausen
,
A.
,
Lundervold
,
A.
and
Gløersen
,
Ø.
(
2023
).
Muscle function during cross-country skiing at different speed and incline conditions
.
J. Exp. Biol.
226
,
jeb245474
. .