Superficial Blood Vessels

Superficial veins appear whenever lifting heavy weights or during a period of intense strength training. The superficial vessels are responsible for carrying the blood from the tissues closer to the skin’s surface to the deep veins.
The superficial veins also manage and monitor your body’s temperature. If your body becomes too hot, the deep veins pushes blood to the superficial veins.
https://www.usaveinclinics.com/blog/difference-between-superficial-and-deep-veins/