STORRS, Conn.—Researchers continue to explore the benefits of different combinations of protein and carbohydrates in exercise recovery, as evidenced by several recently published studies. In a new a meta-analysis coordinated out of the University of Connecticut, Storrs, researchers sought to determine the performance benefits of ingesting a protein-carbohydrate drink during endurance performance (J Strength Cond Res. 2010;24(8):2192-2202. DOI: 10.1519/JSC.0b013e3181ddfacf). A total of 11 studies were included, containing three time-trial and eight time-to-exhaustion cycling protocols; only three studies controlled for caloric content and contained an isocaloric trial. Four of the studies did find significant differences between a protein and control trial, but none were isocaloric studies. Meta-analysis of the time-trial studies found no
significant improvement with protein ingestion. There was a significant effect seen in the time-to-exhaustion studies, although the effect was only significant with isocarbohydrate studies. The average percent improvement with ingestion of protein was 9 percent. The research team concluded coingestion of protein and carbohydrate during exercise did have an ergogenic effect on endurance performance when assessed by time to exhaustion, possibly due to their caloric contribution rather than a unique benefit of protein, although further research is necessary.
One such study was just conducted at the University of Texas, Austin, where researchers looked at whether a beverage with a mixture of different carbohydrates (glucose, maltodextrin and fructose) and moderate protein would increase time-to-exhaustion during endurance exercise, despite containing 50 percent less total carbohydrate than a carb-only product (J Strength Cond Res. ePub 20 Aug 2010. DOI: 10.1519/JSC.0b013e3181ecccca). Trained male and female cyclists (n=15) exercised on two separate occasions at intensities between 45 and 70 percent VO2max for three hours, then at 74 to 85 percent VO2max until exhaustion. Beverages (275 mL) were provided every 20 minutes during exercise—either a 6-percent carbohydrate product (CHO) or 3-percent carbohydrate/1.2-percent protein (MCP). While there were no differences in the combined group, MCP significantly increased time to exhaustion in subjects cycling at or below ventilatory threshold (VT). The researchers concluded a mixture of carbs and a modest amount of protein can improve exercise intensities near the VT.
Another trial at Pennsylvania State University, University Park, also looked at the effects of a protein-carb beverage, this time on perceived soreness and skeletal muscle damage after exhaustive aerobic exercise (J Strength Cond Res. 2010;24(8):2203-10. DOI: 10.1519/JSC.0b013e3181e4f7f9). Researchers recruited seven men to participate in an exercise session consisting of a 30 minute run on a declined treadmill, at a consistent 75 percent maximal heart rate. The men consumed a placebo beverage or cocoa-based protein and carbohydrate prototype drink immediately after exercise, two hours post-exercise and before bed. Ingestion of the prototype beverage had no effect on inflammatory markers or biomarkers of skeletal muscle damage including creatine kinase and urinary isoprostanes. However, subjects consuming the cocoa-based protein/carb mixture did report less perceived soreness at 24 and 48 hours after the exhaustive exercise compared to the control.