Graduate Program

Kinesiology and Sports Studies

Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

John D. (Jake) Emmett


The purpose of this study was to compare the effects of a protein-containing sport drink with a traditional non-protein sport drink has on ratings of perceived exertion (RPE) and finishing speed of an half marathon. Of the possible factors that would support including protein in a sport drink the primary one was its inhibitory effect on serotonin release in the brain. This could help attenuate perceived exertion, thus allowing individuals to compete at a higher level for longer durations (Davis, Alderson, & Welsh, 2000).

This study was conducted using nine members of the Eastern Illinois University Men's Cross Country team. Subjects completed two separate 13.1 mile runs on a flat, crushed limestone path, consuming 4 ounces of either a carbohydrate and protein (CHO-P) or non-protein (CHO) containing sport drink every three miles as assigned by the primary researcher. The study used a single-blind design so the subjects did not know which sport drink they were receiving during each trial. RPE scores were obtained at the halfway point and at the finish line. Finishing speed was also recorded as the speed over the last 1.1 miles of the 13.1 mile run were at a "race pace" effort.

During the second trial, the two groups were given the other sport drink in a crossover design. For purposes of data analysis, subjects were analyzed in four groups (CHO1, CHO-P1, CHO-P2, and CHO2) based upon the sport drink they consumed each trial.

A MANOVA with a Tukey post-hoc test was used to analyze intergroup statistics using SPSS statistical software (version 22.0). The results showed no significant differences between the two groups for RPE and finishing speed at the end of an endurance run. Therefore, there was no benefit was observed in RPE or finishing speed of an endurance run from having protein in a CHO sport drink. Confounding factors include slight differences in weather between trials, differences in individual nutrition and sleep habits between trials, and different levels of effort between the trials. In conclusion, this study found no added benefit of a carbohydrate-protein sport drink compared to a traditional carbohydrate sport drink on RPE or finishing speed at the end of an endurance run.