Yep, seems like a strange question for me to be asking since basically, training variety and unique exercises are what I'm known for! Oddly enough, even though I have a TON of unique exercises, I have training sessions where I do nothing but basic stuff and don't even TRY to come up with new twists on anything. Sometimes, I just take an exercise I know and hammer away at it. Some of the most effective programs I use (including my own programs), have phases where there is almost NO variety at all! And it works like crazy.
The basic exercises are basic for a reason....they work and work well! So how much training variety do I recommend? And when would I suggest switching things up?
Well, that's a tough question - it depends completely on the individual, their goals and their situation. If it's a beginning trainer, extreme variety is not necessary. In fact, they'll do best by sticking to the basic movements for at least a few months. When they learn squats, their body is going to take a long time to develop the proper groove and the proper execution (hopefully!).The beginner improves strength by improving nervous system efficiency, not by increasing muscle size. It's why a beginner's arms will shake like leaves when they do bench presses the first few times! The nervous system isn't co-ordinated and the signals are all over the place. As that co-ordination improves, the movement gets smoother.
So back to the main question. If you're more intermediate to advanced, I would recommend switching up your main exercises at least every three to four weeks. Even more advanced trainers who have a solid base of experience can and should change things up even sooner.
By that, I don't mean do 5 exercises for each bodypart every day to "hit all the angles". That's not necessary and can actually work against you. Training variety should have a purpose. Doing inclines then flat then declines on the bench press in one session is total overkill. Doing that over the course of 3 different sessions - better idea.
Another point with too much training variety is a lack of actual training EFFECT. How do you know if you're improving if you never do the same exercise again any time soon! Your body won't know what to adapt to and won't adapt to anything. That's the reason that sticking with just a few exercises can be so effective - you're only giving the body a few things to adapt to! Another reason that's so effective is that you're practicing the movements so much, you're developing the neurological specificity and efficiency similar to what a beginner sees in their first weeks of training. BIG strength increases in that time are the norm.
Don't get me wrong...training variety is also the spice of life! Personally, I get easily bored with the basics, even though I use them regularly. I'm always looking for better ways to attack the muscle - not just for the sake of doing something different but trying to find ways to make things work better. I encourage you to do the same! I have a feeling you're on this site BECAUSE you have a curious mind and love this kind of physical and intellectual exploration of training practices.
So when you're using unique, new exercises, try everything but keep a note on what works BEST for you. Then work the crap out of THOSE exercises. Not everything works equally well for everybody but when you find something good, train it! Use it again and soon so you DO get a training effect and see direct improvements in it. A good rule of thumb is repeat 75% of your exercises then 1/4 of the time, add in something new and see if it's good enough to replace what you're using.
But on a side note, if the program you're using calls for specific exercises for a specific purpose, USE those exercises. I know for many of my programs, I use specific exercises as tools, for example, flyes to hit the stretched position of the chest. A cross-over won't work there.
Experiment within the confines of the program you're using. Heck, sometimes what I'll do is take a time when I'm between programs and do a general bodypart split. In that split, I will purposefully try and invent things. I'll have a week where I don't do anything twice! These are the fun weeks for me, even when I find stuff that kills me. This is what keeps me going mentally and helps me find things that I'll work into a program in the future.
On a side note to THAT, sometimes I'll set specific conditions on myself to invent things. For example, a few weeks ago, I limited myself to two chairs, a broomstick and a sandbag. That's it! I came up with some great stuff...things I never would have come up with if I hadn't limited myself to specific equipment.
Bottom line, don't go for extreme variety all the time, even if you're advanced. You need some consistency to achieve a good training effect otherwise the body won't know what to adapt to!
By Nick Nilsson