It depends on the sport. Check the average GPA for any top level university gymnastics team. It needs to be a sport that invokes complex coordination of a wide variety of muscle groups.
The basic idea is that while you are learning to do challenging gymnastic (or other physical) skills, the brain is releasing growth hormones to learn the skill. But they aren't targeted. It's hard to grow the part of the brain that does a cartwheel on a balance beam without also growing the part of the brain that does calculus.
The basic idea is that while you are learning to do challenging gymnastic (or other physical) skills, the brain is releasing growth hormones to learn the skill. But they aren't targeted. It's hard to grow the part of the brain that does a cartwheel on a balance beam without also growing the part of the brain that does calculus.