The difference between Primary and Secondary muscles

When it comes to your workout routine, do you know the difference between primary and secondary muscles? There are often lots of misconceptions when it comes to strength training. One thing many people don’t realise is that strength training falls into two buckets; isolation exercises and compound exercises. Think of it in terms of how the exercise trains your body, and how many muscle groups are being used significantly when the exercise is performed.

In this post I’m going to dive into these two types of exercises. We’ll also look at primary and secondary muscles, so that you can aid recovery and avoid over-training.

Isolation Exercises

An isolation exercise is any exercise in which only one major muscle group is trained by itself. That means that the movement is typically performed in such a way where usage of all other muscle groups are avoided and leaves one muscle group isolated and able to do all of the work.

Compound Exercises

A compound exercise is any exercise that involves the use of more than one major muscle group at a time. That means that there is one larger muscle group that ends up doing the majority of the work, and then one or more smaller muscle groups that are recruited secondarily. 

So what does this have to do with primary and secondary muscles?

Primary muscles are the muscles that control the movement you are performing. In simple terms, the primary muscle is the muscle intended and targeted during the exercise. Whereas secondary muscles are what assist the primary muscles to complete an exercise. 

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For example, when performing a squat, the primary muscles exercised are the quadriceps (thigh muscles) and the secondary muscles exercised are the glutes, hamstrings and calves.

Now you know the difference between primary and secondary muscles, you can see how easy it might be to train certain muscle groups more often than you realise because of the secondary usage during compound exercises.  

Learn more about the strength myths you need to stop believing.

The good news is that I plan my workout program very carefully. I always make sure that my program pairs muscle groups up in a way that avoids any potential problems as a result of secondary muscle usage.


I hope that helps bust another misconception around strength training. Remember, if you have any questions please email me. I love hearing from you and always answer your messages personally. Send me an email anytime at


Alexia Clark