Research shows that training three to four times a week may be the most effective frequency to make gains.
In a University of Rio de Janeiro study, subjects were divided into three groups to train with a different weekly frequency: twice per week (Tues., Thurs.); three times per week (Mon., Wed., Fri.); or four times per week (Tues., Wed., Thurs., Fri.). Each group used the same full-body routine each workout. Strength improvements for bench press, lat pulldown, and leg press were measured at four and eight months.
Strength improvements were not significantly different among groups. However, the group training four times weekly did show a greater percentage change from baseline.
Although some studies have shown that training should be performed three, four, or even five times per week, this study suggests that over time, the differences in strength gains between low- and high-frequency training get smaller and smaller. This study also shows that training a muscle group two days in a row might, in some cases, produce the greatest gains.
You shouldn’t worry if you have time to train only twice a week. You can still make good gains over time if you are consistent. A full-body workout may be your best option if you’re training only twice weekly because it will ensure that all muscle groups get adequate attention. - FLEX