Heatstroke It’s dangerous for humans to spend so long time under hot environments, because they may faint with losing a lot of water in their bodies. It’s called heatstroke. Human is thought to contain about 70% water. If the water in your body lowered to less 60%, your life would take a risk of death. To avoid such a situation, you frequently need to drink water, when you move or get exercise in the hot environments above 30 minutes. However, taking in water isn’t sufficient to prevent from the heatstroke. You lose not only the water but also salt while taking sweat. So, I’d like to recommend drinking sport drinks to supply both of them with your body effectively.