. >> coach dan bevilacqua took the usa football course. he knows higher temperatures mean extra safety measures are necessary. >> so we tell kids when the heat index is above 90, we don't wear equipment at all, we do mostly agility drills, and we don't do any contact. >> and they break more frequently for getting water. hydration is a key part of prevention. and it begins well before the whistle blows for practice. [ whistle ] >> we tell them even before the season starts when we address the parents, they should drink at least one liter of water three hours before practice time. >> you've heard the expression, an ounce of prevention is worth a pound of cure. in this case, it's a bottle of prevention, and the wisdom to get off the field if you're feeling thirsty, dizzy or nauseous. >> if you stay out there in the sun and you continue to be in the heat, what happens is you go onto heat stroke. and now what happens is your body can't control the sweating, and you get too hot. and when you get too hot, your body doesn't work right. and that's