Effect of a moderate alcohol dose on physiological responses during rest and prolonged cycling

Aim: We examined the acute effects of a moderate alcohol dose (48g) ingested before prolonged cycling on acute physiological responses in eight healthy males (mean ± SD; 23 ± 2 years; 1.77 ± 0.04m; 75.8 ± 4.1kg).
Methods: In a randomised order, euhydrated participants completed two experimental sessions with the sequence of 150-minutes seated at rest, 90-minutes of cycling (50% V̇O2max), 120-minutes seated at rest. Participants drank 250mL of flavoured squash with or without alcohol (vodka; ~16g) at 10, 40 and 70 minutes of the initial resting phase, giving a cumulative fluid intake of 750ml with 48g of alcohol. Heart rate, blood glucose, breath alcohol concentration and respiratory gases were recorded throughout the entire trial with cumulative urine volume recorded during both rest phases.
Results: Total carbohydrate (control = 115 ± 19g: alcohol = 119 ± 21g; P=0.303) and lipid (control = 17 ± 4g: alcohol = 20 ± 7g; P=0.169) oxidation was similar between conditions. Average heart rate was 7% higher in the alcohol condition (control = 111 ± 12bpm; alcohol = 119 ± 11bpm; P=0.003). Blood glucose concentrations were similar between conditions during (P=0.782) and after exercise (P=0.247). Urine output was initially increased between conditions following alcohol ingestion before diminishing (P<0.001) with no difference in total cumulative urine output (P=0.331).
Conclusion: Consuming an alcoholic drink containing 48g of alcohol in the hour before moderate intensity sub-maximal aerobic exercise led to detectable increases in heart rate and rate of urine production with no effect on substrate use.