Introduction
Long-distance cross-country ski races typically last more than 2 h, depleting muscle glycogen stores in the legs and, to an even greater extent, the arms (Bergström et al. 1973). While carbohydrate (CHO) supplementation demonstrates clear performance-enhancing effects, particularly when ingested during exercise lasting > 1 h and in multiple forms (Jeukendrup 2004), there is limited information regarding the use of CHO during cross-country skiing. Therefore, the aim of the current study was to examine the effect of ingesting two different CHO solutions on 30-km cross-country skiing performance.
Methods
10 male and 3 female trained cross-country skiers (age: 30±7 yr; body mass: 74±9 kg; VO2max: 60±6 mL/kg/min) completed 4 x 30-km classic roller-skiing time-trial efforts (consisting of 6 x 5-km loops) on separate days in a randomised, counter-balanced order on a treadmill. Two trials used a high rate of CHO ingestion (2.4 g/min, HC) and two trials used a lower rate of CHO ingestion (1.2 g/min, LC). In addition, two trials used a high frequency of CHO feeds (6 feeds, HF) and two trials used a low frequency of CHO feeds (2 feeds, LF). The CHO was a 1:1 mix of maltodextrin and fructose and the drinks were provided at 24% and 12% concentrations for HC and LC, respectively.
Results
There were no significant differences in performance over the four trials (140±16, 139±16, 141±18 and 141±18 min for HC-HF, LC-HF, HC-LF and LC-LF, respectively) and when matched for frequency of feeds, there were no significant performance differences between the paired comparisons (i.e., HC-HF vs LC-HF and HC-LF vs LC-LF). Moreover, there were no significant differences in blood glucose concentrations at 5-km intervals when comparing HC-HF with LC-HF (p>0.05) or HC-LF with LC-LF (p>0.05). However, an order effect was detected for performance (143±17, 140±16, 140±17 and 138±15 min for trials 1-4, respectively) with significant improvements from trials 1-2 (p=0.02) and 3-4 (p=0.03).
Discussion
Results from the current study demonstrate no significant differences in 30-km cross-country ski performance when consuming either 2.4 or 1.2 g/min of a mixed CHO solution. Furthermore, there were no significant differences in blood glucose concentrations during exercise between the high and lower CHO trials. However, despite familiarisation to treadmill roller-skiing and the simulated race track, a learning effect was evident. It is concluded that race-track familiarity may have a greater effect on 30-km cross-country ski performance than the rate of CHO ingestion.
2014.