CINCINNATI, Aug. 12 (UPI) -- Teenage athletes who guzzle energy drinks for a competitive edge may find themselves too tired to finish the game, U.S. fitness trainers warn.

The market research firm Mintel said 25 percent of teens drink the caffeine-packed drinks regularly, The Cincinnati Enquirer reported Tuesday.

Nutritionists and coaches in the Cincinnati area are warning high school athletes the drinks can hurt their athletic performance. Nutritionist Cindy Cassell said she has seen football players drink two or three Red Bulls during practice instead of water.

"You can tell who's drinking them because two-thirds of the way through practice, they're done. They can't make it through a two-hour practice," Cassell told the newspaper.