Hmmm, the use of the term 'world-class athlete' mad me curious about how that term is defined these days. The track and field people seemed like a decent source. I would imagine these rules-of-thumb being applicable to skiers, dancers and martial artists as well as ballplayers, since they're actually pretty generic. http://trackandfieldathletesassociation.org/site/a-world-class-athlete-what-are-the-key-attributes/ I like this part: "We all tend to focus too much on strength development. There are certain minimum thresholds of strength necessary to be a world-class athlete. Instead of focusing on maximum efforts, focus on training the appropriate energy systems relevant to your sport."