I want to challenge the idea that a movement is done one specific way, on one specific spring tension, for one specific set of muscle groups—and that that’s the only way to think about it.
Knee stretches gives us a useful place to start. We have a familiar movement, a familiar name and some familiar instructions. But when we change the spring tension or the way we organise the start position, we change what the movement asks of the person doing it.
So let’s look at what is happening in the video below.
What moves, and what stays still?
In the familiar forward-facing version, my hands are on the footbar, my hips are off my heels and my shoulders are behind my hands. I push the bed out and bring it back, trying to maintain the shape of my spine and the angle of my shoulder.
My legs create and control the movement. The muscles around my shoulder and torso work to maintain the shape.
As I increase the spring tension, both jobs become harder. My legs have to work harder to move the bed, and my shoulders have to work harder to maintain their position.
Calling something isometric doesn’t mean the effort stays the same. As the bed travels out and spring tension increases, maintaining that position becomes more demanding.
What are we stretching?
Apparently, knee stretches is for stretching our knees.
I’m being slightly tongue-in-cheek, but it raises a useful question: what do we mean by that?
Three of our quadriceps muscles—the vasti—cross the knee without crossing the hip. Rectus femoris crosses both. So when we think about the length of rectus femoris, we have to consider what is happening at the hip as well as the knee.
In the demonstration, I’m sitting on my heels with my knees already in deep flexion. That gives us something to think about before we assume that moving the bed is creating an additional knee stretch.
Which muscle are we talking about? Which joint changes its length? What additional movement are we creating?
The name alone doesn’t answer those questions.
Less spring tension changes the job
The law of the spring says that the further out the bed travels, the more spring tension there is.
But it’s not enough to say that less spring tension is easy and more spring tension is hard. Spring tension affects the movement depending on the movement.
With heavier springs in this version of knee stretches, my legs push the bed out and control its return. My shoulders work to maintain their position against that increasing load.
When I drop to a half spring, the bed wants to run away from underneath me like a scared cat.
Now my hip flexors have to help pull it back underneath me. Turning on my quads and pushing harder would send the bed further away.
I’ve reduced the spring tension and done almost the same movement, but I’ve changed the job substantially. We have to look at the spring tension, the position and how far the bed travels together.
Where is the weak link?
If we increase the load on a system, the weak link is the thing that can no longer manage it first.
So what happens when we keep adding springs to knee stretches?
My legs might have plenty more to give. But as they push the bed away, my body wants to move forward. My shoulders have to manage that force while maintaining their position.
In the version I demonstrate, the shoulders become the limiting factor. If they can’t maintain the position, I have to change something. I might bend my elbows and come down towards the footbar.
Adding more springs has made the whole system work harder. It hasn’t necessarily allowed me to give my legs the challenge I intended.
Organise the shoulder so the legs can work
If I want to use this movement to challenge my legs, I need to organise my upper body so it can manage the force more efficiently.
The cue I use is to drop the chest and make the arms look like a handstand. Then push the bed out and in.
In the demonstration, I also lower the footbar to allow more travel of the bed. That requires more available range at the shoulder and hip, but it lets me organise the shoulder differently as my legs create the movement.
Changing the footbar also changes the spring tension at the positions I’m comparing. So I have to reassess the springs as well as the shape.
It’s the relationship between those things that matters.
Start with the output you want
I’m not saying that the version we were taught at Pilates school is wrong or that we shouldn’t teach it.
I’m saying we should be clear about what we want it to achieve.
If the output is to challenge the legs while maintaining the shape through the torso and shoulder, increasing the load makes all of those jobs harder. If the shoulder becomes the weak link, we need to change how we organise it so the legs can be the things challenged by the load.
That may mean changing the start position, the footbar and the spring tension.
Forget, for a moment, what the movement is called or what we think it’s for. What output do we want—and how would we organise the movement to create it?
