It’s commonly recommended that you drink eight 8-ounce (237-mL) glasses of water per day (the 8×8 rule).

Although there’s little science behind this specific rule, staying hydrated is important.

Here are 7 evidence-based health benefits of drinking plenty of water.

If you don’t stay hydrated, your physical performance can suffer.

This is particularly important during intense exercise or high heat.

Dehydration can have a noticeable effect if you lose as little as 2% of your body’s water content. However, it isn’t uncommon for athletes to lose as much as 6–10% of their water weight via sweat (1Trusted Source, 2Trusted Source).

This can lead to altered body temperature control, reduced motivation, and increased fatigue. It can also make exercise feel much more difficult, both physically and mentally (3).

Optimal hydration has been shown to prevent this from happening, and it may even reduce the oxidative stress that occurs during high intensity exercise. This isn’t surprising when you consider that muscle is about 80% water (4Trusted Source, 5Trusted Source).

If you exercise intensely and tend to sweat, staying hydrated can help you perform at your absolute best.