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My gymmates told me that if I want to build my muscles, I should concentrate on one part of muscles ( eg: biceps) in one day, then move on to the next part of the muscles the other day. Never ever workout on two or more different parts of muscles on the same day because the muscles won't be built up that way.
I don't find this a compelling argument because if you keep on working out on a part of the muscles, it will experience fatigue and hence the benefit will be diminishing. Won't it be better to train on different part of muscles so that resting time is properly given to the tired muscles?
Who's right on this? What is the proper workout routines as far as muscle building is concerned?