Even cybernetically-enhanced supersoldiers need to work out to stay buff. For a man of few words you need to be able to walk the walk as well as talk the talk and the Master Chief workout is good 'ol plain, solid military fitness. You need strong legs to cover the distance, strong arms to carry a heavy weapon and for those hand-to-hand moments and a core that's simply tireless because your armour ain't made of cotton. If you think the workout's a little on the tough side just suck it up and be stoic, soldier.
Extra Credit: 30 seconds rest between sets.