Sometimes called heat stroke, this isn't an injury per se, but it can lead to one. It can even lead to death. Heat prostration is a risk in any outdoor sport, especially in warm, humid weather. Heat prostration occurs when the body isn't able to get rid of its internal heat as quickly as it builds up. Eventually, when a player's body temperature shoots over 104 degrees Fahrenheit (40 degrees Celsius), the brain itself can start to cook -- and that's a head injury even worse than concussion. Heat prostration can strike when playing baseball in temperatures over 90 degrees Fahrenheit (32.2 degrees Celsius), but there's an easy way of preventing it: Hydration. Keep putting fluids in your body, especially sports drinks like Gatorade that are designed to keep the body's electrolytes properly balanced. Signs of heat prostration include clammy skin, nausea, dizziness and excessive sweating.
If a player starts showing signs of overheating, he or she should be taken out the game and given a chance both to rest and to cool off. It's not uncommon to hear of young athletes driven by overzealous coaches to the point where their body temperatures shoot to dangerous levels. Be careful when playing sports on hot days. A rotator cuff injury will heal with time and maybe a little help from surgery, but a fried brain is forever.