Until the age of 12-13, I got beat up all the time by school bullies because my face was kind of like the other girls (but not the body, I was already pretty strong, tall and lanky even before puberty) and was always playing with the girls during recess (Although, when once and awhile I played dodge ball, I really spiked the hell out of those jerks who went after me).
But, at puberty, I grew taller (but not larger) than all the other boys in my grade school and put on major muscles on my legs and core without even trying. Someone tried to trip me and my legs were like steal, they fell instead, then another day, they tried to put somebody crouched behind me without me knowing and push me over him, they couldn't even move me. The bully left me alone after that. Seeing as being a jock could protect from these assaults, I started doing a lot of competitive sports from then on.