Adding protein to a carbohydrate pre-exercise beverage does not influence running performance and metabolism

To analyse whether pre-exercise CHO + PRO vs. CHO intake distinctly influences running performance and metabolic biomarkers along a various of exercise intensities.In a randomised, double blind, counterbalanced, crossover and placebo control design, 10 middle distance runners were tested in 3 occasions. After 10 h of fasting, participants ingested isovolumic beverages (0.75 + 0.25g·BW-1 of CHO + PRO, 1.0g·BW-1 of CHO and placebo control) 30 min before a treadmill running incremental protocol of 4 min steps until exhaustion. Venous blood was collected at fasting, 30 min after beverage ingestion and after the 3rd and 7th running steps. Oxygen uptake-related variables, including respiratory exchange ratio, heart rate, plasma glucose, insulin, glucagon, free fatty acids, blood lactate concentrations, gastrointestinal discomfort and rate of perceived exertion were measured.The addition of PRO to CHO had no influence on the measured variables, which did not differ between conditions along all incremental protocol intensities. The intake of CHO + PRO (compared to CHO) tended to decrease glycaemia (106.5 ± 21.3 vs. 113.6 ± 26.5) and to increase insulinaemia (14.4 ± 15.1 vs. 12.7 ± 10.8) at intensities close to maximum oxygen uptake.The addition of PRO to a pre-exercise CHO beverage had no impact on running performance and related metabolic variables at a wide spectrum of exercise intensities.