For the most gains from lifting when you want the result to be muscle growth, a man should focus on training every muscle group two times every week. This, according to the results of a research review that was recently published in the Sports Medicine journal.

The scientists conducted an analysis of the results of ten different studies. Their purpose was to compare the rate of muscle growth among men who had trained one time, twice, and three times per week over a span of two months.

What the researchers determined was that when a group of muscles was trained twice per week, it would experience greater growth than it would if it was trained only once. That said, as much as that may sound like an obvious trend, it is more complex than it seems. The scientists also found that even if the number of sets and reps done every week are equal, the amount of muscle growth is still better if it's split into two batches done in each week instead of all done at once.

For instance, if you did three sets of bicep curls on Sunday and another three on Wednesday, then you'd have better results than if you did a full six sets on Wednesday. Even though you technically did the same number of sets, your muscle gain will be better if you split them up into equal amounts done twice per week.

Despite the fact that the scientists felt certain that this was the best way to build, the research review did not reveal exactly why it works this way. That said, while the study's lead author, Lehman College assistant professor of exercise science, Brad Schoenfeld, PhD, does admit that the reason isn't proven, there is a theory.

The belief is that lifting causes muscles to experience growth for a period of time that continues for around 48 hours. Once that time is done, the muscle isn't continuing to grow unless the muscle is trained again, in which case it will start growing again for another span of 48 hours.

Over time, the growth will start to accumulate, so placing the body into a state of muscle building on a regular basis will cause it to have maximum muscle growth.

So why is it better to lift with each muscle group twice per week and not three times? Because there is a limit to the rule. The study showed that people who placed three days between training times had better results than those who placed two days between training times. The reason for that remains unknown.