Eric Roberts argues that training one muscle group once a week caps you at 10 sets per session, but muscles need 10-20 sets weekly for growth. Hitting each muscle twice a week, like chest on Monday and Thursday with 8 sets each, lets you reach that 16-set target and build more effectively.
Here's why working out one muscle group per day, like chest on Monday, back on Tuesday, arms on Wednesday, is not the most optimal in order to see progress. In order for you to see progress, you need to be hitting adequate volume per week for that muscle group. So let's just take your chest, for example. You want to typically be hitting 10 to 20 sets of chest per week. Here's the kicker: in any one given workout, if you do more than 10 sets, You are going to start getting diminishing returns from that workout. So if you're trying to hit 10 to 20 sets of chest per week, but you can only do up to 10 sets max per workout, if you only hit chest one time that week, you can only get 10 sets. So you're hindering your results in the long run, as opposed to if you hit chest on Monday and then Thursday, you can do 8 sets Monday, 8 sets Thursday, get 16 total sets for the week, and you will see better results that way. This is why following something like an upper/lower split instead can be beneficial. Hope it helps.
