...and if you're doing it, you need to STOP doing it, especially if you want to get as big and strong as possible.

I'm going to let Jason Maxwell, one of the creators of the Daily Undulating Periodization program address this.

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Q. Doesn’t training a muscle directly just once a week allow you to hit it harder and build more mass and strength?

No. Quite the opposite, in fact. One of the most critical components in building muscle mass is muscle protein synthesis (MPS).

This is the rate at which your muscles uptake protein and, in essence, how effectively they grow.
About 4 hours after a workout, MPS rises to 150% of its normal resting level. 24 hours post‐workout, it’s still at 109%. Good times.

Unfortunately, after 36 hours, MPS is back to only 14% above baseline, and it returns to normal soon after.

Therefore, by only training a muscle once a week (or even twice a week) you’re leaving a whole lot of increased MPS potential on the table. This is not a wise move if you’re after increased size.

Have you heard the phrase “strength is a skill”?

Essentially, this means that to get good at something, you have to do it a lot. It’s no good wanting your squat to go up and only squatting once a week. Your muscles, joints, and nervous system don’t get adequate stimulus to learn the movement.

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Nick again, here.

I totally agree with what Jason wrote...and it really explains why hitting a muscle/movement more frequently is more effective from a scientific standpoint.

You want to turn your body into a muscle-building MACHINE...a machine that operates all week long, not just in short bursts when you work a specific part.

The SYSTEMIC approach to muscle and strength is WAY more powerful than any piecemeal split training approach like the "once a week" stuff.

Here's another reason why I don't like the "chest day" approach...

When you have a "chest day"... (or any other single muscle group "day")...the first exercise you do is the one exercise you'll be strongest on, right?

So everything you do AFTER that first exercise is weaker than it should be and not as effective at working the target muscle.

You're doing almost your entire workout from a position of weakness in that specific bodypart.

That, to me, says it all...it's one of the major reasons why I don't like that approach as a regular program (it's fine as a specialization approach).

The structure of the training will stop you from ever achieving your true potential with strength and mass. Plateuas are essentially built right into the programming.

The more frequently you can hit a muscle/movement and still manage recovery, the faster the results you'll get, both in strength and mass gains.

THAT is what Jason's "Daily Undulating Periodization" program is all about...strategizing your programming to build strength and muscle efficiently...and it WORKS.