Influence of genotype variations on markers of skeletal muscle recovery from heavy endurance exercise, and on responses to carbohydrate-protein supplementation

Purpose: This study examined the influence of genotype polymorphisms (specifically ACTN3 R577X, IGF-II C13790C, IGF-II G17200A, IGF2AS A1364C, IGF2AS G11711T) on markers of skeletal muscle recovery following an acute bout of heavy endurance exercise, and assessed their role in determining individual responses to carbohydrate-protein supplementation. Methods: Twelve trained male cyclists completed repeated cycling trials, each consisting of an initial session of glycogen-depleting exercise, followed four hours later by a \u3e1 hr time-trial on a computerized cycle ergometer (VeloTron, Racermate, Inc). Subjects were randomly administered a high-carbohydrate low-protein (HCLP), or carbohydrate-only (CHO) beverage, which was consumed immediately and 2-hours post glycogen depleting exercise, and immediately following subsequent exercise. Beverages were isocaloric and isovolumetric. Blood samples were obtained before the glycogen-depleting exercise of the first trial for genotyping analysis. Serum creatine kinase (CK), peak muscle function (MVC), mental and physical energy and fatigue ratings, and muscle soreness ratings were obtained as markers of muscle recovery at specific time points. Subjects completed these methods for both treatments in a double-blind protocol. Results: Changes in MVC were significantly different (P \u3c 0.05) from baseline to 4-hours post glycogen depleting exercise among genotypes for the ACTN3 R577X, IGF-II C13790C, and IGF2AS A1364C single nucleotide polymorphisms (SNPs) during the CHO control trial. Changes in mental/physical energy/fatigue and muscle soreness ratings were significantly different (P \u3c 0.05) from baseline to 24-hours post glycogen depleting exercise among genotypes for the ACTN3 R577X and IGF2AS G11711C SNPs during the CHO control trial. These variables tended to improve with the HCLP treatment when subjects identified for the above genotype variations were analyzed, although the improvements were not statistically significant. Changes in serum CK were not significantly different (P \u3e 0.05) from baseline to 4-hours post glycogen depleting exercise among genotypes analyzed. Conclusions: Genotype variations led to significant differences in MVC, physical/mental energy/fatigue and muscle soreness ratings, which tended to improve with the HCLP treatment. There were no genotype effects for serum CK