A Comparison Of Protein And Carbohydrate-fed Sprint Interval Training On Skeletal Muscle And Performance Adaptations

Abstract

Sprint interval training (SIT) has emerged as a potent metabolic stimulus inducing beneficial musculoskeletal adaptations. However, nutritional support to optimise the adaptive response to SIT remains poorly characterised. Carbohydrate (CHO) has previously been shown to blunt metabolic adaptations to training while there is increased interest in the role of protein in regulating training adaptations. PURPOSE: The aim of this study was to determine the effects of whey protein concentrate (WPC) compared with CHO feeding on the acute regulation of skeletal muscle mitochondrial gene expression, enzyme activity and performance following a 3 week SIT intervention. METHODS: This study was ethically approved and conducted in line with the Declaration of Helsinki. Healthy, recreationally active (VO2 max <50 ml.kg-1.min-1) males (n = 17) were randomised to complete SIT under CHO or WPC conditions. Participants attended the lab after an overnight fast (≥10 h) and ingested 0.33 g.kg-1 body mass (BM) of WPC, or 0.91 g.kg-1 BM maltodextrin (CHO) 45 min prior to SIT consisting of four 30 s sprints at a resistance of 7.5 % BM, interspersed with 4 min recovery. Muscle biopsies were obtained under local anaesthetic from m. vastus lateralis at rest and 3 h post-exercise. RNA extracted from skeletal muscle underwent multiplex PCR to determine mRNA expression relative to reference gene UBE2D2. Independent t-tests determined between-group differences in changes from baseline. RESULTS: Acute changes in PGC-1α, NMRK2, NNMNAT1/3 were not differentially regulated by condition (p > 0.05). Fold-change in PDK4, SIRT4, NAMPT and NNMT were differentially regulated by nutrient condition following an acute bout of SIT (WPC vs CHO: 6.6. vs 2.6; 0.62 vs 0.86; 1.73 vs 1.14; 6.0 vs 2.8, respectively, p < 0.05). Citrate synthase and β-3-Hydroxyacyl-CoA dehydrogenase (HAD) enzyme activity increased to a greater extent in response to SIT with WPC (Fold change WPC vs CHO: 1.3 vs 1.1; 1.23 vs 1.02, respectively, p < 0.05). Post-SIT Wingate performance changes were not different between conditions (% change WPC vs CHO: 6.3 vs 4.1%, p > 0.05). CONCLUSION: Pre-exercise nutrients result in divergent regulation of mitochondrial enzyme activity and some genes in response to SIT, however this is not associated with differential performance adaptations.