Concentrating on one or two muscles a day gives the best results. For example, Chest and Triceps can be done together, while doing chest your tricpe muscle will be used to 30%. so doing triceps on this day gives the maximum benefits. Shoulder has many variations and also it plays a big role how your body shape is, so allocating one day would be beneficial.Lates and lower back on one day Squates and thighs on one day finally Bisceps and Abs on one day. To know more about different varaitons of these exercise Click Here.