I've heard that exercise increases your testosterone level and that it can increase your penis size because of those testosterone, is it true?

Testosterone & Youth: I doubt you will find much in science to back up the claim about testosterone. But, exercise improves muscle energy and fitness, burns off excess calories, keeps you strong and at a lower percentage body fat. Excess fat in a man can lead to increasing estrogen levels and this blocks the natural levels of testosterone. So, keep exercising!