Carbohydrate Before Resistance Exercise Doesn't Alter Performance, Blood Glucose, Or Muscle Glycogen Despite Hormonal Changes

Abstract

PURPOSE: The purpose of this study was to investigate changes in resistance exercise performance, serum insulin, epinephrine, glucose, and muscle glycogen from carbohydrate supplementation. METHODS: Participants completed four sets to failure at 70% of 1-RM with 45s rest on angled leg press with or without pre-exercise carbohydrate (2g/kg) after a 3hr fast. Serum glucose, epinephrine, and insulin were assessed at baseline, 30 min post-ingestion, immediately after, and 1hr post-exercise with or without carbohydrate supplementation. Muscle glycogen was measured at baseline, immediately after exercise, and 1hr post exercise. RESULTS: There was no main effect of supplement on resistance exercise performance (F= 2.169, p=.18). There was a main effect for set on repetitions showing a decrease over sets completed (F=26.18, p<.001) There was no interaction between supplement and set on reps to fatigue (F= .337, p=.79). There was a time effect showing glycogen decreased immediately post-exercise for both groups and remained lower than baseline after 1hr (F= 14.305, p<.001). No main effect of supplement on glycogen concentration was found (F=2.847, p=.13). No supplement time interaction was found on glycogen (F = 1.191, p=.33). There was an interaction showing pre-exercise carbohydrate supplementation led serum glucose to be utilized more during exercise (F= 3.791, p=.026). No main effect for supplementation on blood glucose was found (F= .072, p=.79). Pairwise comparisons indicated no time effect on serum glucose (p>.05). An interaction occurred showing insulin decreased during exercise in the carbohydrate condition (F= 47.14, p=.003). Also, there was a main effect of insulin being elevated with carbohydrate consumption (F= 7.72, p=.027). Pairwise comparisons indicated there was no time effect on insulin concentration (p>.05). There was a main effect of carbohydrate supplement decreasing epinephrine (F=7.924, p=.023). No time effect was found on epinephrine concentration (F=1.475, p=.258). No interaction effect was found on epinephrine (F=1.94, p=.181). CONCLUSIONS: Carbohydrate supplementation before resistance exercise does not improve leg press performance to fatigue or glycogen recovery during 1hr rest despite increased glucose availability.