Muscle Glycogen Utilization during Exercise after Ingestion of Alcohol

Purpose Ingested ethanol (EtOH) is metabolized gastrically and hepatically, which may influence resting and exercise metabolism. Previous exercise studies have provided EtOH intravenously rather than orally, altering the metabolic effects of EtOH. No studies to date have investigated the effects of EtOH ingestion on systemic and peripheral (e.g., skeletal muscle) exercise metabolism. Methods Eight men (mean ± SD; age = 24 ± 5 yr, body mass = 76.7 ± 5.6 kg, height = 1.80 ± 0.04 m, VO2peak = 4.1 ± 0.2 L·min-1) performed two bouts of fasted cycling exercise at 55% VO2peak for 2 h, with (EtOH) and without (control) prior ingestion of EtOH 1 h and immediately before exercise (total dose = 0.1 g·kg lean body mass-1·h-1; 30.2 ± 1.1 g 40% ABV Vodka; fed in two equal boluses) in a randomized order, separated by 7-10 d. Results Muscle glycogen use during exercise was not different between conditions (mean [normalized 95% confidence interval]; EtOH, 229 [156-302] mmol·kg dm-1, vs control, 258 [185-331] mmol·kg dm-1; P = 0.67). Mean plasma glucose concentrations during exercise were similar (control, 5.26 [5.22-5.30], vs EtOH, 5.34 [5.30-5.38]; P = 0.06). EtOH ingestion resulted in similar plasma nonesterified fatty acid concentrations compared with rest (control, 0.43 [0.31-0.55] mmol·L-1, vs EtOH, 0.30 [0.21-0.40] mmol·L-1) and during exercise. Plasma lactate concentration was higher during the first 30 min of rest after EtOH consumption (mean concentration; control, 0.83 [0.77-0.90] mmol·L-1, vs EtOH, 1.00 [0.93-1.07] mmol·L-1), but the response during exercise was similar between conditions. Conclusions Muscle glycogen utilization was similar during exercise with or without prior EtOH ingestion, reflected in similar total whole-body carbohydrate oxidation rates observed.