The present study investigated the effects of periodic carbohydrate (CHO) restriction on endurance performance and metabolic markers in elite endurance athletes.
Twenty-six male elite endurance athletes (maximal oxygen consumption (V˙O2max), 65.0 mL O2·kg−1·min−1) completed 4 wk of regular endurance training while being matched and randomized into two groups training with (low) or without (high) CHO manipulation 3 d·wk−1. The CHO manipulation days consisted of a 1-h high-intensity bike session in the morning, recovery for 7 h while consuming isocaloric diets containing either high CHO (414 ± 2.4 g) or low CHO (79.5 ± 1.0 g), and a 2-h moderate bike session in the afternoon with or without CHO. V˙O2max, maximal fat oxidation, and power output during a 30-min time trial (TT) were determined before and after the training period. The TT was undertaken after 90 min of intermittent exercise with CHO provision before the training period and both CHO and placebo after the training period. Muscle biopsies were analyzed for glycogen, citrate synthase (CS) and β-hydroxyacyl-coenzyme A dehydrogenase (HAD) activity, carnitine palmitoyltransferase (CPT1b), and phosphorylated acetyl-CoA carboxylase (pACC).
The training effects were similar in both groups for all parameters. On average, V˙O2max and power output during the 30-min TT increased by 5% ± 1% (P < 0.05) and TT performance was similar after CHO and placebo during the preload phase. Training promoted overall increases in glycogen content (18% ± 5%), CS activity (11% ± 5%), and pACC (38% ± 19%; P < 0.05) with no differences between groups. HAD activity and CPT1b protein content remained unchanged.
Superimposing periodic CHO restriction to 4 wk of regular endurance training had no superior effects on performance and muscle adaptations in elite endurance athletes.
1Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, DENMARK; 2Section for Sport Science, Department of Public Health, Aarhus University, Aarhus, DENMARK; 3SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, DENMARK; 4Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, DENMARK; 5Department of Infectious Diseases, Center for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, DENMARK; 6Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, DENMARK; 7Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, SWEDEN; 8Swedish School of Sport and Health Sciences, Stockholm, SWEDEN; 9Elite Performance Centre, Swedish Sports Confederation, Stockholm, SWEDEN; 10Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, SWEDEN; and 11Swedish Olympic Committee, Stockholm, SWEDEN
Address for correspondence: Kasper Gejl, M.Sc., Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark; E-mail: email@example.com.
Submitted for publication April 2017.
Accepted for publication July 2017.