Why is the urine little and red and yellow after sweating a lot in fitness?

The human body excretes water in the following ways:

Breathe through the lungs to expel a small amount of water.

Eliminate some water through sweat glands.

Drain a small amount of water through stool.

Water is mainly excreted through urine.

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When the human body is short of water (you are short of water after exercise), the human body will secrete antidiuretic hormone.

Strengthen the reabsorption of renal tubules (water absorption)

Reduce urine moisture and increase urea concentration.

I saw what you said.