not every athlete is going to blow up with a physique like a Jordan Staal or Chris Kreider. In fact, I think we'll wind up seeing Laf and Kakko both fill out pretty well. Chytil is not skinny. He put on some muscle last season and i'd expect him to fill out even more, since hes only 23.
In regards to some of the other players mentioned, we've been down this road. With all of the cardio a hockey player does the muscle strength doesn't always translate into big burly man muscle. Im sure 75% of the Cup winning Vegas team doesnt look like Jordan Staal.
In fact if you train too hard, eat too much and gain too much weight it could actually have the opposite effect on one's mobility and quickness which is needed in todays game. Jordan Staal plays a heavy game so its ok for him to put on some poundage. Kreider is a freak of nature and has it all. Genetics...
Strength training and sport specific exercise plans will yield success on the ice but not necessarily in the mirror - although on the surface questions about Fox and Mika may have some merit to them.
Either way, to me that's more of a Drury roster decision than something an individual like them can really change. Fox isn't your every day player, especially as a defenseman. He's won a Norris and came in 2nd in voting this season so why question the guys physique? Mika, maybe he could gain some muscle mass, but its more mental with him if you ask me. The guy dominates in all areas when he is on.