Wunda Chair Springs and Pedals: How Resistance Really Works

A Wunda Chair looks simple: a compact frame, a pedal, and a set of springs. But those few parts are responsible for most of the differences you feel from one Pilates chair to another.

A classical Wunda Chair may use two springs and one pedal, while a modern split-pedal chair may use four springs and allow each side to move independently. Spring length, strength, mounting position, and pedal design all affect how the chair behaves.

That is why Wunda Chair spring specifications cannot really be understood by looking at spring color or spring count alone. To make sense of the specifications, you also need to understand how the pedal works with those springs.

1. What Springs Are Used on a Wunda Chair?

Most Wunda Chairs use extension springs connected between the chair frame and the moving pedal.

As the pedal moves down, the springs extend. As the pedal returns, the springs pull the pedal upward again. Depending on the exercise, this spring force can act as resistance, assistance, or both.

The traditional Wunda Chair keeps this arrangement relatively simple.

Gratz is a good example. Its Wunda Chair uses two springs with three eye-hook positions for each spring. Both springs work with a single pedal, and changing their attachment positions changes the way the pedal responds.

Balanced Body follows a similar two-spring idea on its Wunda Chair but gives each spring four possible positions. It uses two heavy black springs and lists maximum system resistance at about 83 lb.

These examples show why saying that a Wunda Chair “has two springs” is only the beginning of the specification. The number of mounting positions and the way those springs connect to the pedal are just as important.

2. Wunda Chair Spring Specifications: What Do They Mean?

When comparing Pilates chair springs, you will usually see specifications such as spring strength, spring length, color, and sometimes the type of attachment at each end.

Some manufacturers provide much more detailed information than others.

2.1 Pilates Chair Spring Strength and Resistance

Wunda Chair springs are often described as light, medium, heavy, strong, or extra strong.

These terms help users choose between different settings, but they are not standardized across the Pilates industry.

For example, Balanced Body uses black to identify a heavy chair spring and white for a lighter spring in some of its chair systems. Align-Pilates uses green for its Strong Combo Chair spring and black for Extra Strong.

So a black Pilates spring does not have one universal resistance value.

This matters when comparing chairs or ordering replacement parts. Spring color is useful inside one manufacturer's product range, but it should not be used to compare spring strength across different brands.

It is also worth remembering that a stronger spring does not automatically make every Pilates exercise harder. In movements where the spring helps support body weight, a stronger setting may actually provide more assistance.

2.2 Wunda Chair Spring Length

Spring length is another important specification.

Align-Pilates, for example, uses 47 cm springs with small eyelets on its Combo Chair. Those springs are specifically designed for the Chair attachment system.

This is a good example of why spring length cannot be considered on its own.

Two Pilates springs can both be 47 cm long and still be different parts because they may have different tension, eyelet sizes, or intended mounting systems.

A longer spring is also not automatically stronger than a shorter one. Length has to match the geometry and travel of the specific chair.

2.3 Initial Tension and Spring Rate

Some manufacturers publish more detailed spring data.

Merrithew, for example, provides specifications for its Stability Chair springs that include initial tension and spring rate.

Its heavy Stability Chair spring is approximately 18 inches long, with initial tension around 14.75 lb and a spring rate of approximately 3.888 lb per inch.

Initial tension tells us how much force is required before the extension spring begins to open. Spring rate describes how quickly the force increases as the spring stretches farther.

You do not need these numbers to perform a Pilates workout, but they explain why two springs that look very similar may behave differently once installed on a chair.

3. How Do Wunda Chair Spring Positions Change Resistance?

One of the most useful features of the Wunda Chair is that the same springs can provide several different settings.

Traditional designs often use eye hooks or pegs. Contemporary chairs may use a vertical spring tree or another multi-position mounting system.

Gratz offers three eye-hook positions per spring. Balanced Body's Wunda Chair provides four positions per spring.

Changing the mounting position does more than simply stretch the spring a little farther.

It changes the spring's starting position relative to the pedal. It can also change the angle at which the spring pulls as the pedal moves.

As a result, the same spring can produce a noticeably different pedal response when moved from one attachment position to another.

This is why Wunda Chair resistance settings should not always be thought of as a simple “easy to hard” scale.

A different spring position changes the relationship between the spring and the pedal, not just the spring itself.

4. How Does the Wunda Chair Pedal Mechanism Work?

The Wunda Chair pedal mechanism is built around a pedal that rotates around a fixed hinge or pivot.

The springs connect the moving pedal to fixed points on the chair frame.

When the user presses the pedal, several things happen at the same time: the pedal rotates, the spring stretches, and the angle between the spring and the pedal changes.

This is why the resistance at the pedal cannot be understood simply by reading the stated strength of the spring.

The pedal itself changes how that spring force reaches the user.

Important parts of this relationship include the pedal length, hinge location, spring connection point, and pedal travel.

Where you place your hand or foot matters as well. Pressing farther away from the hinge provides different leverage than pressing closer to it.

This is also why two Wunda Chairs using springs with similar strength can still feel noticeably different through the same movement.

5. What Does Wunda Chair Resistance in Pounds Actually Mean?

Resistance figures can be useful, but they are often misunderstood.

Balanced Body lists its Wunda Chair at up to approximately 83 lb of resistance.

That does not mean the chair contains an 83 lb spring. It also does not mean the user feels exactly 83 lb at every point in the pedal movement.

The figure describes the output of the spring-and-pedal system under a particular configuration.

Balanced Body's Combo Chair provides another useful comparison. It uses four springs and lists system resistance up to approximately 110 lb.

It would be misleading to interpret this as simply being “27 lb harder” than the Wunda Chair.

The Combo Chair uses a completely different pedal arrangement. Its four springs are divided between two independently moving pedal sections.

The resistance number therefore belongs to the whole mechanism, not to an individual spring.

This is one of the most important things to understand when comparing Wunda Chair specifications: spring force and pedal resistance are related, but they are not the same measurement.

6. Single Pedal vs Split Pedal Pilates Chair

The pedal design is one of the biggest differences between classical and contemporary Pilates chairs.

6.1 Single-Pedal Wunda Chair

A traditional Wunda Chair uses one continuous pedal.

Gratz follows this classical layout, with two springs acting on a pedal that moves as one unit. Balanced Body's Wunda Chair also uses a single-pedal design.

Because both sides of the pedal always move together, the spring system can remain relatively simple.

This setup is closely associated with classical Pilates and works well for movements where the hands or feet are intended to work symmetrically.

6.2 Split-Pedal Pilates Chair

A split pedal divides the pedal into separate left and right sections.

Balanced Body's Combo Chair uses four springs in total, with one light and one heavy spring available for each side.

Merrithew's Split-Pedal Stability Chair uses a similar general approach, supplying two light and two heavy springs.

The reason for the four-spring configuration becomes much clearer once you understand the pedal mechanism.

The extra springs are not simply there to create more total resistance. Each pedal half needs its own spring options so that the left and right sides can move independently.

On many split-pedal chairs, the two sections can also be connected when the user wants them to move together as a single pedal.

This makes a split-pedal chair more flexible, but it does not make it automatically better than a traditional Wunda Chair. The two designs simply serve different purposes.

7. Two Springs vs Four Springs on a Pilates Chair

Because spring count is easy to see, it is often used as a shortcut for judging a chair.

But four springs do not automatically mean twice the resistance of two springs.

A classical Wunda Chair may use two relatively strong springs because both act on one pedal.

A split-pedal chair may use four springs because two are assigned to each side. Those four springs may also include different strength levels.

The more useful question is therefore not:

“How many springs does this Pilates chair have?”

It is:

“How are those springs arranged, and what pedal are they controlling?”

Once you know that, the difference between a two-spring Wunda Chair and a four-spring Combo Chair becomes much easier to understand.

8. Wunda Chair Replacement Springs and Compatibility

Replacement springs are where spring specifications become especially important.

A spring that looks almost identical to the original may still have a different working length, tension, end fitting, or intended mounting system.

Align-Pilates provides a useful example. Its Combo Chair uses 47 cm springs with small eyelets specifically designed for that chair. A different 47 cm Pilates spring is not automatically interchangeable just because the overall length matches.

The same principle applies across brands.

When buying Wunda Chair replacement springs, the important details are the chair model, correct spring length, intended tension level, and connection style.

Color alone is not enough.

It is also risky to assume that a spring is suitable simply because it can physically be attached to the chair. If its working length or tension is different, the pedal may begin from a different amount of spring extension or operate through a range the chair was not designed around.

Replacement springs should therefore be treated as equipment-specific parts rather than generic Pilates accessories.

9. How Wunda Chair Springs and Pedal Mechanisms Work Together

Looking at Gratz, Balanced Body, Align-Pilates, and Merrithew side by side makes one thing clear: there is no single universal Wunda Chair spring specification.

Gratz represents the classical approach with two springs, one pedal, and three eye-hook positions per spring. Balanced Body expands the adjustment range on its Wunda Chair and then moves to four springs when it introduces an independently moving split pedal on the Combo Chair.

Align-Pilates shows why physical spring specifications matter, using 47 cm small-eyelet springs designed specifically for its Combo Chair. Merrithew goes a step further by publishing information such as initial tension and spring rate, showing that a spring's behavior cannot be reduced to color or a Light/Heavy label.

These examples also explain why Wunda Chair spring specifications and pedal mechanism details should always be read together.

Spring length, tension, number, and attachment position describe the force-producing side of the chair. The pedal hinge, pedal length, spring connection point, and single- or split-pedal layout determine how that force is transferred into movement.

That is why two Pilates chairs can use similar-looking springs and still behave very differently—and why a useful Wunda Chair specification tells you more than simply how many springs are included.