Quite a few people train like this. You will find a site that uses these moves, in conjunction ith more conventional stuff over at crossfit.com, and there are many blogs out there that support this kind of stuff. Your concerns about limit strength and muscle mass are well grounded though. The crossfit WODs (workout of the day) are arranged so that you still have some limit strength. Coach Rut, though, has taken this into account, and suggests throwing in some ME days a few times a week and mixing them up with the conditioning stuff, i.e. WOD (conditioning), ME, WOD, rest, ME, WOD, ME or WOD depending on how you feel. The ME days are up to you, Could be limits, cdould be 5X5, could be 1-3 core exercises. BTW, lots of police, fireghters, military and MMA types over there at crossfit.