It's generally accepted, aside from a few notable exceptions, that wrestlers nowadays are in peak physical condition.
In order to compete with the consistency that they do, at the level that they do, the roster needs to ensure their bodies are prepared for the rigours of a wrestling career.
The minimum physical requirement of a WWE superstar is at a level many of us will never reach in our lifetimes, and yet to get noticed and pushed by you-know-who, wrestlers need to supersede that base level by some margin.
Some manage to achieve it via a change in diet or workout regime, but generally it just comes down to good old fashioned hard work.
Honourable mentions must go to former WWE wrestlers like Al Snow, Gene Snitsky, and Vladimir Kozlov, who have transformed themselves since leaving the company.
Plus, it's worth noting that Brie Bella and Maryse are competing regularly, looking phenomenal and even performing at the recent Hell in a Cell pay-per-view despite both giving birth in the last year or so.
Nevertheless, they don't make the list, which is appropriately stacked, of the ten wrestlers in the best shape of their lives...