Article by Gill Cummings-Bell BA (Hon’s), M.Sc. MBA. PGCE. ACSP
I believe that to fully understand how to use a spring for a particular movement on any Pilates apparatus—Reformer, Chair or Tower—we first need to understand what a spring actually is and what it does. It sounds obvious, but how often do we simply teach “one red spring”, “two springs”, “make it lighter” or “make it heavier” without really considering what that change is doing to the exercise?
Understanding the spring helps us understand the exercise.
The Genius of Springs
Springs are remarkable devices and one of the oldest and simplest ways of storing and supplying mechanical energy. The springs used on Pilates apparatus are generally extension springs. At rest, their coils are held closely together and the spring is designed to resist being pulled apart. An extension spring can also be manufactured with initial tension. This is the force already present within the spring that holds the coils together and which must be overcome before the coils begin to separate.
Once the spring starts to extend, another characteristic becomes important: its spring stiffness or spring rate. In simple terms, this describes how much additional force is required as the spring is progressively lengthened. Therefore, when we describe a Pilates spring as light, medium or heavy, we are describing a practical difference in its force and tension characteristics—but we should not assume this is simply a difference in initial tension. As we apply force and extend a spring, we are doing work on it and storing elastic potential energy within it. The further the spring is extended within its normal working range, the greater the restoring force it produces. When we allow the spring to shorten again, some of that stored elastic potential energy is transferred as the spring attempts to return towards its original resting length.
This creates what we commonly experience on the Pilates apparatus as spring tension and restoring force.
Although the term resistance is commonly used in mechanics and by manufacturers, throughout our Pilates teaching I prefer to talk about spring tension and spring force, as these terms encourage us to consider what the spring is actually doing within the movement rather than simply whether an exercise feels harder or easier.
In simplistic teaching terms, we can therefore think about two things:
We apply force to extend the spring, and we apply force and control to manage the spring as it returns.
However—and this is important—the spring does not always simply oppose the client. Depending upon the exercise, the spring can provide tension, assistance, support or stability, and sometimes more than one of these within the same exercise. This is where understanding springs becomes really interesting for us as teachers.
Take Long Spine, for example. As the springs shorten, they exert a restoring force on the carriage. Through the rope, pulley and strap system, this changes the forces being transmitted to the feet and can assist and influence the trajectory of the legs and pelvis.
Compare this with the Foot Series, where we apply force to move the carriage away, progressively extending the springs and storing elastic potential energy. We then use Centring and Control to manage the restoring force as the carriage returns.
So rather than simply thinking:
“Heavy spring = harder exercise”
we need to start thinking:
“What is the spring doing within this exercise?”
That is a very different teaching question.
Wouldn’t It Be Easier If We Had a Digital Dial?
Wouldn’t it be lovely if every Reformer had a digital dial telling us exactly how much force the client was experiencing at every point in an exercise?
Unfortunately, ours don’t!
In reality, spring behaviour is influenced by several factors including initial tension, spring stiffness, the amount the spring has been extended and the construction and characteristics of the spring itself. Without measuring all of these variables, as teachers we rely heavily upon our knowledge of the apparatus, our observation of the client and our understanding of the intent of the exercise. This becomes an even greater teaching challenge in a group Reformer environment.
Not All Springs Are Created Equal
Another complication is manufacturing.
There is no universal Pilates industry standard stating that a spring described as light, medium or heavy must provide a particular force.
Likewise, spring colour is not a universal measurement of spring tension or force.
A red spring on one manufacturer’s Reformer should not automatically be assumed to have the same characteristics as a red spring—or any similarly labelled spring—on another manufacturer’s apparatus. This applies whether the apparatus is described as classical/traditional or contemporary. Joseph Pilates understood the remarkable potential of springs and incorporated them extensively into the apparatus he developed as part of his Contrology method. The Universal Reformer itself evolved over time. Early versions used different spring configurations before the familiar classical configuration of four Reformer springs became established.
Classical manufacturers generally aim to preserve the characteristics and principles of Joseph Pilates’ apparatus, while contemporary manufacturers have developed Reformers using a variety of spring combinations and tension levels. On many contemporary Reformers we may therefore find four, five or even six springs with different tensions described as extra-light, light, medium, heavy or extra-heavy. These may also be colour coded. Again, those colours and descriptions should not automatically be transferred from one manufacturer to another.
Neither approach is inherently better.
The important question is not:
“Are classical springs better than contemporary springs?”
The useful question is:
“Do I understand the springs on the apparatus I am teaching on?”
Because ultimately, spring selection should relate to the client, the exercise and the intent of that exercise. There are of course other variables to consider—the age and condition of the springs, gear-bar position, carriage starting position, rope length, pulley arrangement and even the anthropometrics and lever lengths of the client.
I will leave those for another article!
Application of Springs
Now for a bit of science—skip this bit if it isn’t your bag!
Springs absorb and store mechanical energy when they are deformed and can subsequently release that stored energy as they return towards their resting position.
For an ideal spring, Hooke’s Law describes the relationship between the amount a spring is extended and the force it produces.
In its simplest form:
F = kx
Where:
F = spring force
k = spring constant or stiffness
x = change in spring length
For an ideal spring without initial tension, the elastic potential energy stored within it can be described as:
PE = ½kx²
Where:
PE = elastic potential energy, measured in joules.
Real Pilates extension springs may also have initial tension, so their behaviour is slightly more complicated than the simple equation above. Once initial tension is considered, the force required during extension can be thought of approximately as:
F = Fi + kx
Where Fi represents the initial tension.
Don’t worry—I am not suggesting we start teaching Reformer classes armed with calculators!
The important teaching point is much simpler:
As the length of a spring changes, the force produced by that spring changes.
Therefore, the force experienced by our client is not necessarily constant throughout the movement.
And that has important implications for how we teach.
Spring Tension/Weight Does Not Equal Exercise Difficulty
This is perhaps the most important point in this article.
A heavier spring does not automatically make an exercise harder.
Equally:
A lighter spring does not automatically make an exercise easier.
Changing the springs changes the mechanical relationship between the client and the apparatus.
Depending upon the exercise, increasing spring tension may create:
greater spring force, greater assistance, greater support, increased stability, or a different requirement for control.
Reducing spring tension may decrease the absolute force required to move the carriage but simultaneously increase the client’s requirement to stabilise and control their body.
Think about some of our standing Reformer repertoire.
Reducing the spring may make the carriage easier to move in terms of absolute spring force—but potentially considerably more challenging to control.
So what have we actually made easier?
This is why simply describing springs as making exercises easier or harder can be misleading.
We should instead ask:
What is the intent of this exercise and what effect is this spring having on that intent?
Know the Apparatus You Are Teaching On
Spring characteristics can be measured and tested during equipment development and manufacturing, and manufacturers may provide information about their spring systems, tension levels, inspection procedures and replacement recommendations.
When purchasing apparatus, I believe it is worth asking questions.
How are the different spring tensions determined?
What do the manufacturer’s spring colours or classifications actually represent?
How are the springs quality controlled?
How frequently should they be inspected?
When does the manufacturer recommend replacing them?
Can replacement springs from another manufacturer safely be used?
If a supplier cannot adequately answer these questions, I would at least consider that an amber flag and investigate further. The same principle applies to teacher training. Does your training simply tell you which spring to use, or does it teach you why you are using it? Does it help you understand how changing the spring affects the exercise, the exercise intent and the individual client? Can you explain why you have selected a particular spring rather than simply saying, “because that’s what I was taught to use for this exercise”?
For me, this understanding should underpin teaching across the Pilates apparatus system.
So What Is the Point?
If you teach on classical apparatus, understand the springs on that apparatus and how they influence the repertoire. If you teach on contemporary apparatus, understand the springs on that apparatus. If you teach across several manufacturers, understand that the colours and descriptions may not transfer directly between them.
The principle remains the same.
I often use the analogy of driving a car. Those of us who drive may own and drive very different cars. The controls, power, handling and characteristics differ, but we understand those differences and adapt how we drive accordingly. Pilates apparatus is no different.
Understanding spring tension and spring behaviour is important because changing a spring can alter the tension, assistance, stability, control requirements and ultimately the intent of an exercise.
It isn’t simply about whether the spring is classical or contemporary.
And it certainly isn’t simply:
Heavy = harder. Light = easier.
Springs all work according to the same fundamental mechanical principles. Our job as teachers is to understand the apparatus we are using, understand the person we are teaching and then apply that knowledge to the exercise intent we are trying to create. When we understand initial tension, spring stiffness, restoring force and the role the spring is playing within an exercise, we can begin to make spring selection genuinely client-centred and intent-led.
And perhaps that is the real genius of the Reformer.
The spring isn’t simply providing tension.
It is part of the exercise.
