@chris1975 Hey @chris1975
I'm K Boges, so I thought I would offer my take.
My general take is this...
How much variety really depends on your training status and preferences. Most of the time, I like a bit less variety for beginners, and a bit more variety for more advanced people. A lot of this is because more variations become accessible as you get stronger, but also because beginners often benefit from a more fixed exercise selection to help ingrain motor patterns efficiently. I think many advanced people benefit more from having variation in loading and intensity across the week as a way of maintaining motivation, managing fatigue, and ensuring broad stimulation of musculature, whereas beginners can make linear progress from week to week, and often session to session. The strength and rapid progress beginners make opens the door for more variation later and usually serves as a good source of motivation.
Now for the nuance.
The research on the topic is somewhat equivocal. In some contexts, a limited exercise selection can yield better gains, probably because constantly introducing novel exercises to beginners presents a "learning" threshold that prevents those unskilled with novel exercises from extracting the most benefit from them. Part of making "gains" is getting good enough with a movement to feel comfortable enough to push it. On the other hand, some research shows more variety resulting in superior gains, and this probably has to do with the fact that more variation, in both load and selection, will expose and challenge more muscle. So generally speaking, some variation is good, but if that variation is too broad or too infrequently revisited, then progress could suffer, particularly in beginners. But, there is more to this picture. There is also research showing that more variety can improve motivation, which could translate to better long term adherence, which is a hugely under appreciated component of any program. Anecdotally, I've worked with some people who do not like variety at all, and find the steady and evident progress that results from doing the same thing each training day very motivating, even if that progress is incredibly slow. There is nothing wrong with this. It works. I also have clients that prefer a "conjugate method" approach, and prefer to cycle through variations daily, only to revisit the same exercises every so often. I've seen some incredible gains made this way. It works. And, for others, I will have them perform and cycle through only a handful of variations. It works too. I've personally done both as well. I've had blocks where I only have three variations per movement pattern, and some blocks where I just feel doing something totally different every day. Both worked. Pretty much all approaches will work provided they are performed with adherence to good fundamentals.
So here's the deal, as I see it...
As long as you are training hard, using the appropriate volume, staying injury free, training movements that are congruent with your goals, using excellent technique, and doing this for a long time (I don't mean 8 weeks, but make it a lifestyle), you are going to be fine. Having these fundamentals in place is what really matters. I have a general approach I like to use with most people, and that is from less variation to more variation over time, but at a certain point, I'm primarily concerned with programming in a way that maximizes an individuals adherence, and this necessitates some personalization, both in terms of preference, but also injury predisposition. If you like variety or find yourself prone to overuse injuries, include more variety. If you prefer a limited exercise selection, then limit your variations to a few key exercises.
Over your life, you should take several different approaches to training. Don't be afraid to experiment with an approach for a few months. Training is also a learning experience. Real progress in training comes not from the details, but more from the constant and persistent adherence to good fundamentals.
Let me know if you have any questions. I'm happy to clarify.