Combined metabolic gas analyser and dGPS analysis of performance in cross-country skiing

The purpose of this study was to provide a more detailed analysis of performance in cross-country skiing by combining findings from a differential global positioning system (dGPS), metabolic gas measurements, speed in different sections of a ski-course and treadmill threshold data. Ten male skiers participated in a freestyle skiing field test (5.6 km), which was performed with dGPS and metabolic gas measurements. A treadmill running threshold test was also performed and the following parameters were derived: anaerobic threshold, threshold of decompensated metabolic acidosis, respiratory exchange ratio  =  1, onset of blood lactate accumulation and peak oxygen uptake ([Vdot]O2peak). The combined dGPS and metabolic gas measurements made detailed analysis of performance possible. The strongest correlations between the treadmill data and final skiing field test time were for [Vdot]O2peak (l · min−1), respiratory exchange ratio  =  1 (l · min−1) and onset of blood lactate accumulation (l · min−1) (r  =  −0.644 to − 0.750). However, all treadmill test data displayed stronger associations with speed in different stretches of the course than with final time, which stresses the value of a detailed analysis of performance in cross-country skiing. Mean oxygen uptake ([Vdot]O2) in a particular stretch in relation to speed in the same stretch displayed its strongest correlation coefficients in most stretches when [Vdot]O2 was presented in units litres per minute, rather than when [Vdot]O2 was normalized to body mass (ml · kg−1 · min−1 and ml · min−1 · kg−2/3). This suggests that heavy cross-country skiers have an advantage over their lighter counterparts. In one steep uphill stretch, however, [Vdot]O2 (ml · min−1 · kg−2/3) displayed the strongest association with speed, suggesting that in steep uphill sections light skiers could have an advantage over heavier skiers.