This approach allowed him to train all muscle groups in such a short time. (fitnessandpower.com)
In fact I noticed clients who could previously only train each muscle group once every 5 - 7 days, gradually became capable of training at much greater frequency. (advancedhumanperformance.com)
When training a muscle group twice per week this really allows you to specialize and focus on one type of training at a time. (directlyfitness.com)