A sports drink with a shot of protein may give endurance athletes some extra juice, new research suggests.

The study of 15 male cyclists found that a sports drink containing carbohydrates and protein appeared to boost endurance better than a traditional carb-only sports drink. It also seemed to lessen the muscle wear-and-tear that comes with intense exercise.

While water may be enough for the average moderate exerciser, it’s thought that sports drinks, with their added carbohydrates and electrolytes, may be the better choice during long workouts. The idea of adding protein to the mix is that it may further stretch an athlete’s endurance, and possibly aid in repairing the muscle damage that occurs during grueling exercise.

The new study compared Accelerade, a brand of sports drink with a dose of whey protein, with the carb-only standby Gatorade. It found that trained cyclists pedaled further when they refueled with the protein-fortified beverage.

The findings suggest that for endurance athletes, a protein-containing sports drink may be the way to go, lead study author Dr. Michael J. Saunders said in a statement.

Athletes in sports where “endurance and recovery are critical,” such as running, cycling and tennis, could benefit, according to Saunders, who directs the Human Performance Lab at James Madison University in Harrisonburg, Virginia.

The university’s School of Kinesiology and Recreation Studies funded the study, which is published in the July issue of the journal Medicine & Science in Sports & Exercise.

Saunders and his colleagues tested the sports drinks by having trained cyclists pedal a stationary bike to the point of exhaustion while replenishing with either the protein-added or carb-only drink every 15 minutes. The athletes performed a second, more demanding ride the next day. One to two weeks later, they went through the process again, this time with the other drink.

Saunders’ team found that the men lasted 29 percent longer during the first test and 40 percent longer during the second test when they drank the protein-containing drink.

There were also signs of less exercise-induced muscle damage, according to the researchers. After the exercise tests, the cyclists’ blood levels of creatine phosphokinase - an enzyme released from muscles under stress - were lower when they consumed protein during the workout.

It’s “plausible,” Saunders and his colleagues note in the report, that the drink aided protein synthesis and repair of muscle fibers.

However, they also point out that the extra calories in the protein-added beverage may have contributed to the performance benefits. They say more research is needed to see whether “specific protein-mediated mechanisms” should get the credit.

Saunders, himself a competitive endurance athlete, told Reuters Health he now drinks sports drinks with protein while exercising. “And that’s probably the strongest recommendation I can give,” he said.

The fact that adding protein to a sports drink appears to protect people from muscle damage suggests that they may feel less sore after a heavy workout, and get more enjoyment out of exercise as a result. “The day-to-day grind of training simply becomes easier,” he said.

Saunders added that none of the researchers involved in the study have any relationship to PacificHealth Laboratories, Inc., the maker of Accelerade.

SOURCE: Medicine and Science in Sports and Exercise, July 2004.