Ultimately, the key to building muscle is to have a good stimulus that is achieved with intensity and quality in training, as well as with a good rest to allow recovery and adaptation to the stimulus, ie, to allow muscle development.
Many of us will say that the results are only seen if train daily, we can inform personal experiences is not necessary, and clarify that rest is essential for the growth possible, and training intensity representing the stimulus for therein.
To meet all these characteristics in just 3 or 4 days a week, the most useful among most is to use a split routine that allows train each muscle group a stimulating intensity and at the same time that the area worked rest until next week .
Give muscle group to train at 2 or 3 and dedicate them one day, no more than 1 hour and a half, is the most appropriate, but we should not forget the intensity and for this it is essential to use weights between 70 – 80% of our maximum strength, 3-4 sets with 12 to 15 repetitions each. Although That is, it will achieve a high intensity work soon.
Also, as you progress in training can apply different training techniques that add intensity, for example, in series descending and ascending reps weight training for pyramids, supersets, among others.