Cross‐country skiing movement factorization to explore relationships between skiing economy and athletes' skills

We investigated the relationships between the biomechanics of the double poling ( DP ) technique in cross‐country skiing, its economy, and athletes' skill. To this aim, skiers' motion has been factorized into components through principal component analysis ( PCA ). Eight high‐level ( HL ) and eight regional level ( RL ) male cross‐country skiers performed a 5‐minute submaximal DP trial while roller skiing on a treadmill at 14 km h −1 and 2° incline. Whole‐body kinematics was recorded with a motion capture system. PCA was applied to markers coordinates to extract principal movements ( PM k ), which were ranked by their variance. Energy cost ( EC ) of locomotion was calculated from ergospirometric measurements. Results showed that 96.7%±0.6% of total skiing pattern variance can be described with the first three PM k. (Shoulder and trunk flexion‐extension are described PM 1 and PM 2 and elbow flexion‐extension are mainly represented in PM 2 and PM 3. The variance of further components, consisting of residual movements (eg, slow postural changes or high‐frequency vibrations), was greater for the RL than the HL skiers (4.0%±0.5% vs 2.6%±0.3%; P <.001) and was positively correlated with EC ( R 2 =.646; P <.001). PCA permitted to describe the biomechanics of the DP technique through a limited set of principal movements. Skiing skills and economy appeared to be related to a skier's ability to simplify movement complexity, suggesting that an efficient skier is better able to reduce superfluous movement components during DP .