United's strength and conditioning coach, Mike Clegg, says Fletcher has struck the perfect balance between football fitness and gym work. The only other person he's seen do that is Cristiano Ronaldo.
Fletcher told manutd.com: "Fitness has never been a problem, but in terms of strength and power my gym work has made a real difference. Striking the right balance is important. There'd be no point in bulking up if that was to the detriment of being able to get around the pitch, which is a big part of my game.
"I wanted to get to a level where I had strength, but also the stamina to keep going over 90 minutes. I've found a good balance, although I reckon I could still do a little more and put on more weight without affecting my fitness. There's room for improvement but, like I said, I'm always looking to develop the little things. It's not just the physical side - it's a mental thing as well. I have more experience now, and simply being at this club improves you as a player; being in this team, around these great professionals.
"It's been a gradual progression for me, but I'm really enjoying myself and I want that to continue for many more years to come."