Time between training the same body parts is now at 72 to 96 hours. Example - I last trained shoulders and arms on Wednesday and will not do so until this Sunday.
Mentzer was an average man but an above average bodybuilder. if that's damning him with faint praise, so be it. I don't think he was a genius for stating the obvious but if common sense is so rare that it's a super power, then Mike was loaded with common sense and shared it with any and all that would listen with more than their ego.
