Effect of fatigue on double pole kinematics in sprint cross-country skiing.

The aim of the present study was to examine the effect of fatigue (physiological, mechanical, and muscular parameters) induced by a sprint simulation on kinematic parameters (cycle, phases, and joints angles) of the double pole technique. Eight elite skiers were tested for knee extensor strength and upper body power both before and after a three-bout simulation of sprint racing. They were video analyzed during the final part of the test track of bouts 1 and 3 using a digital camera. Results showed that skiers were in a fatigue state (decrease of the knee extensors voluntary force (-10.4+/-10.4%) and upper body power output (-11.1+/-8.7%) at the end of the sprint. During bout 3, the final spurt and cycle velocities decreased significantly (-7.5+/-12.3%; -13.2+/-9.5%; both p<.05). Angular patterns were only slightly modified between bouts 1 and 3 with trunk, hip, and pole angles being significantly greater for the third bout. The decrease of hip and trunk flexion and the lower inclination of the pole during the poling phase suggested a reduced effectiveness of the force application which could lead to a decrease in the cycle velocity.