A study from the University of Montana in Missoula shows that athletes recover from hard workouts faster in room temperatures of 72 F than in 91 F (International Journal of Sports Medicine, August 2010). Nine male participants completed one- hour time trials at 91 degrees F, followed by recovery in rooms at 91 degrees F or 72 degrees F. They were given recovery carbohydrate beverages at zero and two hours. Four hours after the time trial, the athletes in the air conditioned room had much higher muscle glycogen levels (105 vs 88 mmol/kg).
Intense exercise causes the soreness that signals muscle damage that is necessary for muscle growth. Intense exercise also depletes your muscles of glycogen. The faster you replace glycogen, the quicker you recover and the sooner you can exercise intensely again. Athletes who can take the most intense workouts with adequate recoveries improve the most. This study shows that in hot weather, you will replace used-up muscle glycogen faster in air conditioning than at higher temperatures.