How EXACTLY does hydration (or lack of it) affects your running training or exercise in general. What is the science behind it?

Question

You can feel the difference but how does it work exactly?

In: Biology

Answer 1

A large part of it is that you need your cooling system to work by having water in you to sweat. Sweat helps rid your body of bad stuff that is carried out by the water. Without enough water, your organs can’t work properly because the water helps your blood pump more freely.
At least that’s my most high level explanation.