HARRISONBURG, VA — Sports drinks with protein may be a better option for long workouts, suggests new research. The protein may help with endurance and muscle repair, although more research is needed.

The study pitted Accelerade, a brand of sports drink containing whey protein, against protein-free Gatorade in a battle of endurance. Results were published in the journal Medicine & Science in Sports & Exercise.

The study had 15 cyclists guzzle a sports drink every 15 minutes while pedaling on a stationary bike to exhaustion. The next day, cyclists performed another more demanding ride. One to two weeks later, they performed the whole process again, except with the other sports drink.

Cyclists lasted 29 percent longer during the first ride and 40 percent longer in the second workout when they drank the protein drink. The cyclists' blood levels of creatine phosphokinase — an enzyme muscles release under stress — were lower when cyclists drank the protein drink suggesting that the added protein helped with muscle repair.

While the results are promising, researchers caution that the extra calories in the protein drink may have contributed to the results, and for moderate exercisers water is usually enough for a workout.