What happens when the human body's vital fluids are lost? The body's perspiration rate during exercise can reach as much as two liters per hour, and athletic ability is severely impaired when fluid loss exceeds 2% of body weight.

Source: Guidebook for the Prevention of Heat Stroke During Sports Activities, Japan Sport Association

The Japan Sport Association names 5 precautions that should be taken to prevent heat stroke during sports activities

1. 1Take the environmental temperature into account
2. 2Ensure your body is accustomed to the heat
3. 3Ensure an appropriate supply of fluids and salts
4. 4Wear clothing appropriate for conditions
5. 5Pay attention to the individual's physical condition.

The appropriate supply of fluids and salts is an important way to prevent dehydration.

Diminished performance due to inadequate rehydration is a major problem for athletes and those who exercise regularly. While performance diminishes with the loss of fluids through perspiration, thorough rehydration allows for performance levels to be maintained.

Experiments in the correlation between dehydration / rehydration levels and step aerobic exercise indexes as indicators of aerobic exercise capacity