Individual muscles have their own characteristics and respond to training differently.
No matter how many times you squat or train your legs in a week your lats won’t care. This is why ‘bro training’ where you hit every muscle 1-2x/ weekisn’t optimal for intermediate to advanced trainees. One muscle may require 3-4 sessions a week whereas another may need 2 sessions a week with way less total work sets.
In an optimal program volume and frequency are assessed on a muscle by muscle basis, and then that volume is distributed across a week in whatever way makes the most sense from a training quality and logistical standpoint. This often means training 2/3 of the primary muscle groups each training day, or training with a full body split where each mucle is hit with a different number of sets.
Another way to think about it is that someones arms can be at a novice training level and their quads can be at an advanced training level. If you have a Crossfit athlete that wants to build muscle this becomes especially noticeable as the bulk of their training is done with compound lifts that develop the primary muscle groups and they seldom do isolation work for smaller lagging muscles.
In these cases athletes need to be careful with the volume they use for undeveloped muscles. They may know that they can train upwards of 20 sets a week of ‘upper body pulling’ and ‘upper body pushing’, and as a result they might assume that that is an appropriate amount of volume for their delts or biceps. Or, in another instance they may be conditioned enough to handle 20 sets of bicep work due to the sheer volume of chest to bar pullups and gymanstics work they do on a weekly basis, but their ‘optimal’ volume for progress may be much lower
There’s a difference between what you can handle in terms of training volume and what gives you bennefit. For example, I can train my back every day of the week without any major issues coming up and while still making some training progress. But, is that optimal and could I make better gains at a lower volume ? Based on my experience, the answer is yes. This is a trap that many athletes fall into. They assume more is better and they fall into the confirmation bias trap when theyare able to pull it off injury free. But, that doesn’t mean it’s right for them. This applies not just to hypertrophy work, but to alltraining disciplines
4 sets through
Plate hammer curl-max set @ 15kg
Plate hammer curl-max set @ 10kg
Plate hammer curl-max set @ 5kg
Rest 30 secs
Plate skull crusher-max set @ 15kg
Plate skull crusher-max set @ 10kg
Plate skull crusher-max set @ 5k