There are a lot of different theories about how often you should train, according to a new review in the journal of Sports Medicine, in order to achieve the most gains you should be aiming to train each muscle group twice per week.
Scientists analyzed 10 prior studies that compared muscle growth in people who trained each muscle group once, twice, or three times per week over a couple months, as a result of this they found that when you train a muscle group twice per week it stimulates the most muscle growth, even more so than training three times per week!
A key factor to this research is not only how often you train per week, but also how you spread out your workouts. The research carried out found that doing three sets of biceps curls on Monday and three sets on Thursday will make for bigger biceps than if you do six sets on Monday.
Now this does seem a little odd, but there is a theory behind this. Lifting triggers growth in a muscle for a window of time that lasts about 48 hours. After that 48 hour period the growth will stop and you will no longer be building muscle, this is of course unless you trigger further growth by training the muscle again, which will spur growth for another 48 hours. That growth will accumulate over time, so the more frequently you put your body into a muscle-building state, the bigger your muscles will be.
But here’s the catch, this is only up to a certain point. The research showed people that spread their sets over three days per week experinced similar gains to people who trained twice a week. Scientists aren’t sure why this is the case.
In light of these findings researchers suggest splitting your training into upper- and lower-body days, do two upper-body days and two lower-body days per week.