Maybe (not) . . .
I don't know about "rate" but testes need to be kept cool at lower temperature than body which is why they're hanging out in scrotum. That's why some specialists recommend wearing boxers rather than briefs & avoiding hot tubs.
Some will also fix varicoceles that might warm up testes. But there's no food to eat, vitamin to take or exercise
to perform to increase rate. Waiting a few days can incr #.