combat athletes do do juice, specially at high levels, just like any other sport, but in MMA/boxing, guys juice to recover from daily injuries or recovering from intense training and the toll it takes on your body, crazy strenght isnt a factor in MMA or boxing, most important is cardio, technique and explosiveness, who cares how much u can bench or deadlift, it has nothing to do with fighting, as a matter of fact it can really hinder your abilities as a fighter, just look at 5times world strongest man, marius, horrible fighter