When it comes to training frequency, there’s really two ways of talking about it.
There’s the systematized manner that lays out general guidelines. This system is extremely helpful because it prevents people from getting overwhelmed and gives a great framework to approach lifting. The issue with this system is that it just lacks the ability to give individual recommendations, which isn’t so much a weak point as much as it’s just the nature of systematizing things. General rules help make general decisions, not specific ones. They’re great starting points
The second way I like thinking about training frequency is through the lens of readiness. While I have a general, systematized approach to my programming, I allow myself to have 1-2 exercises per day as wiggle room for muscles that seem to already be recovered. When I’m not doing powerlifting-specific blocks of training, this is extremely helpful to getting results for muscle gain. An example would be something like this. My biceps feel fresh, absolutely no soreness, but I have nothing on my program for biceps that day. I don’t have biceps programmed for the next day either. So, because I know it won’t immediately interfere with anything, I go ahead and do some bicep work for the day! This allows me to program a bit better for the next week (since I’ll likely add an extra day of biceps if the trend continues), and if nothing else, it allows me to get more weekly volume in, which leads to more muscle.
To make this really simple, I put together a flow chart:
Note: This is more powerlifting or powerbuilding specific. If you’re just doing bodybuilding, I’m fairly sure you can reduce this down to step one (is the muscle already sore?).
The more volume you get, the bigger you can grow. The typical difficulty with volume is too much in one day often has more negative effects than positive. So, if you can manage to have more volume spread across more days without reaching that threshold where you can no longer recover… why not?
Now go see what body part is telling you it needs more volume and give it some!