Do you ever wonder how often you should change you training programme? Let's take an objective look at why you would do this, and some logical reasons for when and how to do it. Just a warning: this will be a longer article as this is a somewhat complicated topic.
Variety / Variation This is sometimes called a principle of training, although I'm not sure I believe it's important enough to be a principle. I'll discuss that later though. Variety is basically the idea that making changes to a training program can lead to positive adaptations (more muscle, more strength, etc.). These changes could include anything from changing the exercise(s), volume, intensity, frequency, or rep ranges.
Should We Vary Things? There are generally two main reasons given for using variation: 1. To avoid the law of accomdation / diminishing returns 2. To avoid overuse injury The Law of Accommodation This essentially refers to the phenomenon whereby as we get better at something, we see less results, less quickly. For example, going from a 40kg bench to 80kg may take just one year, whereas doubling your strength again to bench 160kg would take most people multiple years and much more effort. The claim is that by changing things up, we can make more progress than if we just keep things the same. There is not much research to back this up, although the training practices of most successful lifters seems to indicate a certain level of variety is required as you become more advanced. Overuse Injury This one is fairly easy to understand. The more we do something the more likely it is that we're eventually going to get banged up. Runners have more ankle and knee injuries than lifters, who have more shoulder and lower back issues. However what's not clear is whether this is because of the receptiveness of the movements, or merely a consequence of pushing for progress over for a long period of time. Just consider this: we do thousands of reps of walking everyday without getting injured. This would lead me to believe that most injuries are due to trying to progress the load too much.
Is Variety Actually Just Specificity? Remember that specificty relates to training with our goal in mind. Therefore any changes that we make to a programme are done so because we think it will make our training more specific to our goal. Here's an example. Many lifters will decide at some point to gain some muscle mass to help with their strength. They don't get stronger just because they started doing something different, it's because they targeted a specific weakness that was holding them back.
Why Beginners Shouldn't Vary If you're newer to training, you possess the superpower of beginner gains. Remember that this a magic power that you will only have once in a lifting career. You should by now be aware of the principles of specificity and progressive overload. These essentially mean that our body will get good at whatever we do repeatedly, and continued improvements will depend on our training continuing to get harder. The problem with changing your training is that it interrupts the steady process of improvement your body can make on an exercise. The first few weeks of improvement at an exercise are mainly neural (learning efficient technique). When your body becomes efficient at performing a certain exercise, you can use more weight and do more reps, which leads to strength and muscle gains. If you switch exercise, you will have to do a few sessions with lighter weight until you learn how to fire your muscles correctly, which is a wasted opportunity for getting bigger and stronger. Obviously this will eventually come to a halt, but you shouldn't change exercises until you need to. Additionally, just sticking to a handful of exercises makes it much easier to track your progress. Changing things all the time will muddy the waters and make things unnecessarily confusing.
Why Intermediates Should Use Variation As I mentioned above, it's unclear whether variation for its own sake is necessary, but it could help improve gains past the intermediate phase, and it could help deter injury. When it comes to the injury part, listen to your body. If one exercise is hurting and you can do a similar one with no pain, then make the change! Additionally, as an intermediate you may decide to shift your focus with regards to what your goals are. You may want to get good at different exercises, or you may wish to focus on developing certain muscle groups. On top of this, the reality is that doing the same thing for too long can become boring for people. The only people who really have to stick to a plan 100% of the time are professional athletes, and even a few of them will go off-plan every now and then for some mental refreshment. So if variation is the thing that will keep you going to the gym, then use it.
The necessity for training variety is still largely unknown
Variety occurs naturally as a by-product of specificity
Beginners should use little/no variation until it's required
Intermediates and above should experiment to find what works for them