One of the studies, published in BioMed Central's open access Journal of the International Society of Sports Nutrition, specifically focused on whether carbohydrate sports drinks or carbohydrate and protein sports drinks were better for recovery from exercise. For the study, cyclists rode bikes competitively against virtual opponents, and then rested for six hours. During the rest period they either drank carbohydrate sports drinks or the combination of protein and carbohydrate. Both drinks contained the same number of kilojoules. Then, the cyclists raced again. John Berardi of Precision Nutrition who collaborated on the study with the University of Western Ontario said, "Liquid carbohydrate and protein supplements given early during a six hour post-exercise recovery period helped subjects better maintain subsequent time trial performance and power output, compared to supplements with carbohydrate alone". He noted that although both groups had reduced performance during the second race, “The reduction in distance travelled and power output during the afternoon exercise was significantly less among those who had the protein and carbs drink, relative those who just had the carbs". In addition, those who had the combination drinks reported less fatigue.
Another study failed to demonstrate improved performance during exercise when a combination protein and carbohydrate drink was consumed during exercise. The study, conducted by researchers from McMaster University, is published in the August edition of Medicine & Science in Sports & Exercise. Cyclists performed three separate simulated 80 km races. During the races, they were given either a sports drink, a drink supplemented with protein, or a placebo. The results indicated that the sports drink improved performance compared to the placebo drink, but that there was no additional benefit from consuming the protein-supplemented drink. Martin Gibala, an associate professor of kinesiology at McMaster, says, "Previous studies that suggested protein was beneficial used 'ride to exhaustion' tests that do not resemble normal athletic competition. In addition, the subjects in those studies received less than the optimal recommended amount of carbohydrate," says Gibala. "Our study shows that protein confers no performance benefit during 'real life' exercise when athletes consume sufficient amounts of a sports drink."