What percent body water loss impairs a person's physical performance?

Answer 1

You can start losing performance when you lose as little as 1% of your normal body water. If you weigh 160lbs, it would mean that you could start seeing some detrimental effects after you lose 1.6lbs.

However, sports where weight categories exist (Wrestling, boxing, weight lifting, rowing), it is not uncommon for athletes to lose up to 10-15lbs of water just before their weigh-in (2-3 days of very low water intake and a low carb diet to prevent water retention).

Recovery from such dehydration usually takes 24-48 hours. If carbs were removed from the diet, recovery may be even longer.

Answer 2

Depends on how you do your calculations.

Total body fluid, extra-cellular fluid, blood volume?

It also depends on "performance" (i.e. running or doing math?)

BUT even 1 % (that would be about 500 cc) will produce measurable changes by most modes of measurement.

Answer 3

As far as I'm aware the percentage is just 1% when it starts having a physical effect. If you feel thirsty then you are already dehydrated. Hope that helps