Let me explain desensitization a bit better.
In reality what happens is that your body becomes so well adapted to strength training stimulus that it no longer needs to adapt. We could say that the body is fully adapted and that the session no longer represents a stress.
This cannot be done in 4 weeks (Look like a bodybuilder, performance like an athlete is a 4 weeks plan) or even 8. Maybe it can happen after 12 weeks or so, which is why with athletes I work with (even if they don’t lift 6-7 days a week) after a 12 weeks training cycle they will take a week off or dramatically reduce the amount of training for 1-2 weeks.
Training every day ALL THE TIME certainly is not recommended. With more training frequency comes faster adaptations (that’s why elite olympic lifters train 5-6 days a week, often twice a day). So if you always train 6-7 days a week you should have faster progress but also hit the wall sooner.
“Yeah but Christian, didn’t you just said that elite olympic lifters train every day? Why are they still progressing?”.
Because they continue to increase the demands on their body by increase frequencyt and/or tonnage (volume) over time.
For example an olympic lifter my start training 2-3 x per week when he is a beginner. Eventually that will increase to 4 times per week when progress stalls at 2-3 x.
Then it’s bumped up to 5, even 6.
When the body becomes fully adapted they throw in 1 or 2 “two-a-days” during the week, bumping the workload to 7-8 sessions per week.
When progress stops more two a days are included, now they might do up to 10 sessions per week.
The Kazakhtani team train up to 3x per day during their competiton prep, up to 15 sessions per week.
Desensitization might not be the right word. Fully adapted is a better term.
Now, elite athletes who do this for a living can afford to increase workload for years (up to the 15 sessions per day). So when they are fully adapted to intense loading 6 days a week and stop progressing, they can further increase the adaptative load by increasing frequency even more.
The average person cannot do that because of time constraits and a higher stress level. As such, that person doesn’t want to fully adapt quickly. That’s why training 6-7 days a week all the time is not optimal for long term progress. But as part of a long term plan that includes periods of 3-4 (or even 2) sessions per week, it will allow you to spike progress for a short while, allowing you to bypass a plateau. Then you go back to a more normal schedule.
Furthermore you must understand that not all lifting sessions are equal. In the Look like a Bodybuilder… plan more than half of the workouts are fairly low demands. These do not pose the same adaptative demands as an all-out workout.