Its all about the message! The logo and the tag line, which ever one works best (i'm still undecided myself but leaning towards the first one) should represent a frame of mind that people can relate to.
When trying to improve or develop, in which ever way that may be (professionally, physically, health wise) we need to possess or show some type of 'grit'. Some times we need to 'grit our teeth' and get on with it or give which ever obstacle is in your way everything you've got to over come it.
It needs to be a statement that demonstrates that when they are wearing the garment in the gym, on their run etc (almost like when a superhero puts on their costume) they are now in a frame of mind that shows they are going to 'grit their teeth' , get the job done and give everything they've got to reach their goal... Its a message that shows (whether you are 5% body fat or 18 stone, male, female, young, old, beginner, experienced) that they are not intimidated by their environment or surroundings and that they have something which many people don't have or share something that few have...the ability to knuckle down, grit their teeth and go for it!
The ideas below are just doodles or brands I have purchased from in the past or whose branding I think is good. The only problem with these brands are they target people already lean, fit and shredded (as the second one promotes!) I want my logo to be able cover all bases and inspire all areas of the gym going community.