People who dont need restdays dont work hard enough in their workouts or arent doing the smart thing :-)
I used to lift 6 times a week, became prone to injuries so I knocked back a bit. Been working out 4 to 5 days a week and have seen much better results. The harder you work out, the more rest your body needs. Your body is great at indicating when you need to rest up more (e.g. soreness, etc...). Get a feel of what your body is trying to tell you, rest up, then kill it at the gym the next day.
The best indicator for rest is you...if u feel sore dnt as u advance in fitness level ur plain just able to do more most pros hav on and off seasons during an on season they may utilize body splits so killing one group of muscles while resting others keeps thm training longer and harder they may not hav rest days but by training smart and years if experience they knw how to rest without rest days...injuries r anther indicator tht more rest is needed somtimes as with kris gethin frm bodybuilding.com it could b due to genetics tht a specific type of training was to hard tht guy is pro all th way..bottom line whn comes to rest u got to listen to u
I'm going to exercise each Monday, Wednesday, & Friday as one of my new year resolutions