I fail to see any logic in the assumption that athletic people would have more trouble learning something athletic. It depends on the level of the athlete, and how adaptable they are. If you have someone that spends 15 years learning a specific sport, and then they try to learn a completely different sport, they may have trouble getting their old patterns and muscle memory retrained. They will nonetheless still have far, far greater athletic ability than someone who has done nothing, right? Doing nothing doesn't make you better at anything. And I submit to you that someone who has achieved a high level in any one sport is likely to be a naturally gifted athlete. More so than someone who has done a little of this and a little of that. And again, greater athletic ability cannot but be an advantage in an athletic endeavor.