The effects of beer consumption on the physiological responses to submaximal exercise

In this study six subjects (4 males, 2 females) exercised for 45 min on a cycle ergometer at ~50%, V̇O₂max on three occasions. Fluids (beer, B, or water, W; 1.25 ml·kg^-1 at 5 min intervals) were administered during two of the experimental sessions. No fluid (N) was administered as a control. Mean skin temp (T̄sk), rectal temperature (Tre), and heart rate (HR) responses were determined. Oxygen consumption (V̇O₂) and carbon dioxide production (V̇CO₂) was measured utilizing open circuit spirometry during min 13, 28, and 43. The respiratory exchange ratio (R) was calculated from respiratory data. Venous blood samples were taken by indwelling catheter prior to the onset of exercise and at min 15, 30, and 45. Serum was harvested and later analyzed for Na⁺, K⁺, Cl^-, and glucose (GLU). HR, T̄sk, and Tre responses were unremarkable with no significant difference between treatments. R was reduced across time for W and N and was significantly less than B by min 30. Similarly, GLU dropped continuously across time for W and N but was unchanged for B. Serum Na⁺ and K⁺ concentrations were significantly elevated across time but no difference existed between groups. These data suggest that beer has no obvious benefit as a replacement fluid during exercise of this intensity and duration. The maintenance of resting GLU levels is thought to be a consequence of the carbohydrate (maltose) found in this beer.