Physiological determinants of performance in modern elite cross-country skiing
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This thesis consists of four studies with additional unpublished results, in which the main objective was to examine factors that determine performance in modern elite cross-country (XC) skiing. Thirty-two elite male XC skiers volunteered to participate, with some subjects participating in several studies. Maximal aerobic power, maximal anaerobic capacity, O2-cost and performance was measured during rollerski skating on a treadmill to investigate differences between techniques (V1 and V2), differences between skiers, and changes in these variables during an annual training season. In addition, a novel approach involving PET/MRI scanning was used to investigate muscle use at low- and high-intensity exercise in double poling (DP). The studies together demonstrate that performance in elite male distance skiing (> 15 km) is highly related to VO2max, exemplified by the findings that the best skiers reached values of 83 ± 3 mL·kg- 1·min-1. Sprint skiing (< 1.8 km) performance has somewhat different physical and physiological demands, as sprint skiers have a larger body-mass index and a significantly higher anaerobic capacity compared to distance skiers. With systematic testing of elite skiers during an annual training year VO2max was unchanged and the increased performance was related to enhanced O2- cost and anaerobic capacity. The observed constant VO2max across the yearly training cycle, and the finding that VO2max is not related to increased performance during an annual training season, seems contradictory to results obtained during the 1980s and is likely related to changes in training habits of elite skiers in recent decades. With respect to propulsion technique, there were no differences between V1 and V2 in O2-cost or performance, but individual differences occurred and therefore, choice of skiing technique is likely important for the individual skier. The present results further suggest that with increasing intensity during DP, the legs contribute significantly to the total increased energy turnover. Hence, specific training is not only related to exercise modes but also to the intensity of exercise performed by the skier.Paper I: Losnegard T, Myklebust H, & Hallén J (2012). No differences in O2-cost between V1 and V2 skating techniques during treadmill roller skiing at moderate to steep inclines. Journal of Strength and Conditioning Research 26(5):1340-7.Paper II: Losnegard T, Myklebust H, & Hallén J (2012). Anaerobic capacity as a determinant of performance in sprint skiing. Medicine & Science in Sports & Exercise 44(4):673-681.Paper III: Losnegard T, Myklebust H, Spencer M, & Hallén J. Seasonal variations in VO2max, O2- cost, O2-deficit and performance in elite cross-country skiers. Journal of Strength and Conditioning Research (Accepted).Paper IV: Bojsen-Møller J, Losnegard T, Kemppainen J, Viljanen T, Kalliokoski KK, & Hallen J (2010). Muscle use during double poling evaluated by positron emission tomography. Journal of Applied Physiology 109:1895-1903.
Avhandling (doktorgrad) - Norges idrettshøgskole, 2013