Question

Why is it that when some people are fit that their veins pop out??

Answer 1

Answer: High-intensity weightlifting causes your muscles to enlarge. In turn, that causes your veins to move toward the surface of your skin and pop out more. To build muscle, do strength-building workouts with a high number of reps, heavy weights, and short rest breaks between sets.

Explanation:  hope this helped

Answer 2

Explanation:

This is due to rising blood pressure and/or body temperature. For example, when you are working out, the blood flow, in the area where your veins pop out, increases.