Carbohydrate supplementation during prolonged cycling exercise spares muscle glycogen but does not affect intramyocellular lipid use

• DOI: 10.1007/s00424-007-0236-0
• Publication Date: 2007-02-26T14:27:33Z
• Authors: Trent Stellingwerff; Hanneke Boon; Annemie P. Gijsen; Jos H. C. H. Stegen; Harm Kuipers; Luc J. C. van Loon
• Keywords: Lipid Oxidation; Carbohydrate Metabolism

Using contemporary stable-isotope methodology and fluorescence microscopy, we assessed the impact of carbohydrate supplementation on whole-body fiber-type-specific intramyocellular triacylglycerol (IMTG) glycogen use during prolonged endurance exercise. Ten endurance-trained male subjects were studied twice 3 h cycling at 63 ± 4% maximal O2 uptake with either glucose ingestion (CHO trial; 0.7 g CHO kg−1 h−1) or without (CON placebo water only). Continuous infusions [U-13C] palmitate [6,6-2H2] applied to quantify plasma free fatty acids (FFA) oxidation rates estimate lipid use. Before after exercise, muscle biopsy samples taken IMTG content. Plasma rate appearance (R a) substantially greater in vs CON trial. Carbohydrate resulted a lower first hour exercise trial, resulting 38 19 57 22% decreased utilization type I II muscle-fiber content, respectively. In both FFA R subsequent concentrations lower, 34 12% reduction (P < 0.05). intake did not augment utilization, as microscopy revealed 76 21 78 content We conclude that does modulate but spares initial stages men.