is it true when you do your legs when going to the gym and using free weights.a natural testosterone is released which is in your buttocks this then makes your top half 15% bigger.
Bit dubious about the buttocks bit, doesn't testosterone come from your nuts?. Any major systemic exercise (squats, deadlifts etc)will have have an effect on muscle size. Muscles and fitness magazine quoted an experiment where college football players where given different exercise routines. The group with heavy systemic exercises put on the most muscle mass overall.