Yep it has to do mainly with nervous system recovery which is a big deal when trying to gain strength. I practice what I preach either with this routine:
mon- chest, tri
tue- legs, abs
wed- off
thur- delts, abs
fri- back, traps
weekend off
or MY PERSONAL favorite:
Day #1 PULL (traps, back, biceps, rear delts)
Day #2 PUSH (chest, delts, triceps)
Day #3 off
Day #4 Legs (butt, quads, hams, calves)
Day #5 off
Day #6 off
mon- chest, tri
tue- legs, abs
wed- off
thur- delts, abs
fri- back, traps
weekend off
or MY PERSONAL favorite:
Day #1 PULL (traps, back, biceps, rear delts)
Day #2 PUSH (chest, delts, triceps)
Day #3 off
Day #4 Legs (butt, quads, hams, calves)
Day #5 off
Day #6 off