Effects of carbohydrate dose and frequency on metabolism, gastrointestinal discomfort and cross-country skiing performance

This study investigated carbohydrate ingestion of varied doses and frequencies during a simulated cross-country skiing time-trial. Ten men and three women (age: 30±7 y; V ̇O2max: 59.6±5.7 mL·kg-1·min-1) completed four, 30-km classic technique roller-skiing time-trials on a treadmill. A 1:1 maltodextrin-fructose carbohydrate solution was provided at high (2.4 g∙min-1; HC) and moderate (1.2 g∙min-1; MC) ingestion rates, each at high (six feeds; HF) and low (two feeds; LF) frequencies. While performance time was not significantly different between trials (140:11±15:31, 140:43±17:40, 139:12±15:32 and 140:33±17:46 min:s in HC-HF, HC-LF, MC-HF and MC-LF, respectively; p>0.05), it was improved with trial order (p<0.001). There was no effect of order on any other variable (p>0.05). In the LF trials blood glucose was elevated following carbohydrate ingestion (at 4 and 19 km) but was reduced at 14 and 29 km compared to HF strategies (p≤0.05). Gastrointestinal discomfort was higher in HC-LF compared with all other trials (p≤0.05). Whole-body lipid oxidation was lower and carbohydrate oxidation was higher in LF compared with HF trials (p≤0.05). Altering carbohydrate dose or frequency does not affect cross-country ski performance. However, low frequency carbohydrate ingestion resulted in poorer maintenance of euglycaemia, reduced lipid oxidation and increased gastrointestinal discomfort.