All, I keep hearing that one needs to have rest periods in between workouts, at least a day. My question is though that if you work out one muscle group one day (ie. chest and tri's) then the next day you do a different muscle group (back and bi's), does that count as a rest period for your chest and bi's?

You wouldn't be working the same muscle group in consecutive days, so that would give them a day off. But as far as molecular chemistry and biology is concerned, I keep hearing that if you overtrain, you tend to break down and may even get sick.

Any comments would be appreciated.