I received a question from a male asking me why do testicles get hard. First, this is very normal. They do this for two reasons: Warmth and Arousal.
When a male is cold, the testicles will move closer to the body to make sure that the sperm stay at perfect production temperature. In return, if a male is too warm, they will move down to cool down from high body temperature.
Yes, normal. They're supposed to do that when they're cold to keep the testicles at optimal sperm producing temperature, which is a few degrees below body temp. So when the air surrounding the scrotum is too cold, it tightens and brings the testicles closer to the body for warmth. When its hot out, it does the opposite, and the scrotum relaxes and lets the testicles hang low as far away from the body heat as possible. Also, stress and or anxiety can cause tightening as well.
The second is arousal. When a man has an erection or is extremely aroused, your testicles will tighten as well. The closer to ejaculation, the tighter they can become.
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