Effects of net efficiency of roller skiing using the diagonal stride on cross-country skiing racing performance

Abstract

A roller skiing test in the field that uses mechanical efficiency to assess cross-country skiing performance has not been established. Thus, in this study, the net efficiency, a definition of mechanical efficiency, during roller skiing was determined using the diagonal stride technique, and the net efficiency at racing speed was estimated to determine the relationship between net efficiency and racing performance in cross-country and roller skiing and to evaluate whether net efficiency could be a determinant of racing performance. Eight male collegiate crosscountry skiers were assigned to high- and low-level groups (n = 4 each) based on their cross-county skiing performances. Two-dimensional kinematics and oxygen uptake were determined forthe skiers while they were diagonally roller skiing at various speeds on a level track. The net efficiency was calculated from the total mechanical work rate, which is comprised ofthe rates of internal and external work, and thenet energy expenditure. The rates of total mechanical work and net energy expenditure at racing speed were estimated by substituting the mean racing speed into individual regression equations obtained forthe experiment, and the net efficiency at racing speed was calculated from the estimates. Racing performance during roller and cross-country skiing was found to be directly correlated (r = −0.915, p=0.001). Net efficiency was higher throughout most of the speed range (p=0.029) and at racing speed (p = 0.029) in the high-level group compared with the low-level group. These findings revealed that net efficiency is one factor that determines racing performance during crosscountry and roller skiing and that higher net efficiency enhances racing performance.The diagonal roller skiing test on flat terrain, which was proposed in this study, could bea newfield test for assessing the performance of cross-country skiers.