Date Published: June 29, 2017
Publisher: Public Library of Science
Author(s): Vegard Rasdal, Ronny Fudel, Jan Kocbach, Frode Moen, Gertjan Ettema, Øyvind Sandbakk, Laszlo Csernoch.
Nordic combined (NC) is an Olympic winter-sport performed as a ski jumping (SJ) event followed by a cross-country (XC) pursuit race employing the skating style.
To elucidate the associations between sport-specific laboratory capacities and SJ, XC skiing, and overall NC performance in a world-cup NC event.
Twelve international world-cup NC athletes from 8 nations performed laboratory testing one day prior to participating in a world-cup NC event. Squat jumps and SJ imitations (IMIT) were performed on a three-dimensional force plate, whereas XC skiing-specific physiological characteristics were obtained from roller ski skating tests on a treadmill and an all-out double poling (DP) test. Finally, body composition was measured. Laboratory capacities were correlated against performance in SJ, 10-km XC skiing, and overall NC in the world-cup event. Multiple regression analysis was used to determine the best suited laboratory variables for predicting performance.
Vertical IMIT velocity together with body-mass provided the best prediction for SJ performance (r2 = 0.70, p<0.01), while body-mass-normalized V˙O2peak and DP power provided the best prediction for XC performance (r2 = 0.68, p<0.05). Body-mass-normalized V˙O2peak was the only significant correlate with overall NC performance (r2 = 0.43, p<0.05) in this competition. Overall, the concurrent development of V˙O2peak, upper-body power, and SJ-specific vertical jump capacity while minimizing body-mass within the BMI limit set by FIS should be considered in the seasonal training of NC athletes.
Nordic combined (NC) is a traditional Olympic winter-sport, and is performed as a ski jumping (SJ) event followed by a cross-country (XC) pursuit race employing the skating style over a distance of 5–15 km (standard competition is 10 km). Both events are carried out on the same day with 1–3 hours in between, where each athlete starts the XC race with a time disadvantage per point lost to the winner of the SJ event. Consequently, NC athletes need to perform well in two fundamentally different sports; SJ that requires well-developed explosiveness and jumping technique and XC skiing where aerobic energy delivery and skiing efficiency are key determinants [1–4].
The study was approved by The Norwegian Data protection Authority. All participants signed an informed consent from before the experiment and were made aware that they could withdraw from the study at any point without providing an explanation. The study was conducted in accordance with the Declaration of Helsinki.
The present study investigated associations between sport-specific laboratory capacities and NC world-cup performance in NC athletes who combine well-developed explosiveness and SJ technique with aerobic energy delivery capacity and XC skiing efficiency. Our main findings were as following: 1) vertical velocity obtained in an imitation jump (VvIMIT) and body-mass provided the best prediction of SJ performance; 2) body-mass-normalized V˙O2peak and double poling (DP) power provided the best prediction of XC performance; 3) body-mass-normalized V˙O2peak was the only significant correlate with overall NC performance. In addition, the benchmark values provided for the best performing athletes in SJ and XC skiing among NC athletes further support the importance of these factors for the specific events.
Vertical IMIT velocity and body-mass in combination best predicted SJ performance, whereas body-mass normalized V˙O2peak and upper-body power best predicted XC skiing performance. The test capacities provided for the best SJ and XC skiers among our 12 NC athletes may serve as reference values for world-class performance in these events. Specifically, the 3 best SJ obtained a group mean of ~2.5 m·s-1 vertical velocity in the imitation jump with a body-mass of <60 kg, with the respective values being 12–15% different among the 3 best XC skiers. Interestingly, there was only 5% difference in vertical velocity in the squat jump between the two performance groups, which indicates that performance in the sport-specific movement of an imitation jump distinguishes performance groups more than pure vertical jump capacity. The 3 best XC skiers showed a group mean of >76 ml·kg-1·min-1 in V˙O2peak and upper-body power of 344 W and 5.1 W·kg-1, being respectively 5%, 21%, and 6% higher than the 3 best SJ.