According to a new report that was published in the journal Sports Medicine, the ideal amount of time each week that you should be training each muscle group is twice. To determine this the scientists involved in the study looked over the past results of ten other studies. Then they compared the findings between people who had worked out each muscle group once, twice, or three times in a week.

They found that working each muscle group twice a week leads to more gains that doing it once a week which sounds sort of obvious, but that holds true even if the overall amount of reps stays the same. So if you did ten reps one days a week on a single body part it would still not create the same amount of growth that you would get from doing five reps on the body part two different days a week. The researchers aren’t sure exactly why this is, but they have confirmed it.

The theory as to why this works, is that after you lift weights there is a 48 hour period where the body can build muscle in that area, and then it backs off. However if you train the muscle again, then it is renewed for another 48 hour period. Basically the longer that you can keep your muscles in the muscle building state, the more likely they are to keep building.

However this only works up to a certain  point. The researchers also determined that if you spread out those sets over three days instead of two, the body will not gain more muscles than it would if you were only doing it two days a week. That’s a good thing to keep in mind when you’re planning workouts, because you could just be wasting time overtraining muscles when they aren’t able to respond.

It does make sense that gains would naturally tap out at a certain point, since your body only wants to grow so big. The more muscle we have the more calories we burn which we might want, except that our biology tries to be careful to ensure that there is enough food to even feed and sustain us.

So what this means for application into your workout, is that if you are splitting up your workouts into upper and lower body ones you should do each two times a week. But if you are doing full body training, then you should aim to do it three days a week anyway since it’s probably not enough training to try and hit all the body parts in just the two days.

As always though, getting in a regular workout is better than nothing, so if you aren’t specifically focused on gains then just aim to get your 45 minutes most days a week, incorporating both weight training and cardio.