How many times you train a muscle group per week is often a highly debated topic. Traditionally, especially in bodybuilding circles, it's believed that training a muscle group once a week is the best approach to growing muscle. This is mainly due to the belief that if you train a muscle more than once in a given week, it can lead to 'overtraining' and doesn't allow adequate time for your muscles to grow. Although there is limited research on the topic, one summary of research showed that training muscle groups twice per week led to more growth than training them that once...