In this post we discuss why strong muscles don’t reduce the forces at your joints and why that’s good news if you suffer with joint pain.
There’s a common misconception that strong muscles reduce joint pain by limiting the forces acting on them.
You’ll see this is in the media and on both personal training and physiotherapy websites.
Whilst it’s true that getting stronger can help to reduce joint pain, it’s important to have an accurate understanding of the mechanisms involved. Faulty concepts can lead to training errors and more pain rather than less.
Why strong muscles increase the forces at your joints
Let’s take the knee as an example because this is the most frequently referenced joint when this concept is discussed.
This biomechanical modelling study found the quadricep muscles exert significant forces on the ACL and the patellar tendon. They also found the quadriceps increased the contact forces between the tibia and the femur (tibiofemoral joint).
The stronger the quadriceps, the greater those forces are. Just as a more powerful car exerts greater force on anything it tows.
If stronger muscles increase the forces at joints, why do they help reduce pain?
To answer this question we have to move away from biomechanical explanations, which clearly aren’t the full picture, and think more about the motives of the nervous system.
As I’ve discussed before, pain is an output of the nervous system that’s predicated on its assessment of the threat.
Let’s take two contrasting situations to help explain this concept.
Imagine you have a knee that occasionally causes you pain (perhaps you don’t even have to use your imagination). Despite this, you get roped into running a half marathon.
Which of the following two approaches do you think would most likely lead to you finishing the event without knee pain?
1. You figure the less running you do the less likely it is you’ll hurt your knee. As a result you turn up to the start line having only run 5km in preparation.
2. You’re concerned about your knee so you embark on a strengthening programme of the muscles surrounding it. You incrementally increase the total distance you run each week by no more than 10% and back off if you feel your knee getting sore.
Unless you’re new to this, I’m pretty sure you said 2. The question is, why?
It’s accurate to say that less force would go through your knee with the first approach. In fact, the second approach is more likely to produce a painful response at some stage.
There’s little doubt, however, that the second method is more likely to have you completing the event without pain in your knee.
Pain represents a mismatch between the capabilities of the joint and the task at hand
In the first scenario, the nervous system is being asked to manage a significant physical demand with almost no preparation.
The gap between what the joint has been exposed to and what’s being asked of it is enormous. The brain, registering this mismatch, has every reason to intervene with pain as a protective response.
In the second scenario, the joint has been progressively loaded over time. The nervous system has accumulated evidence that the knee can handle increasing demands, and crucially, that it can recover from them.
Summary
This is why strength training reduces pain. Not by shielding tissues from force, but by systematically exposing them to it.
So getting stronger doesn’t reduce the forces at your joints, it increases them. By doing so it reduces the threat the nervous system perceives.