If you’ve ever been coached to “control is the hard part” on the Reformer, Cadillac, or Arm Springs, you’ve been doing one of the most underappreciated forms of strength training: eccentric loading.
Eccentric training is the muscle action that happens when a working muscle lengthens under tension—the “lowering” phase of a squat, the “return” of a row, the “coming back in” of the carriage. In Classical Pilates, springs make that eccentric phase unavoidable. You don’t just push tension away—you must close the springs with intention, resisting them as they want to snap you back.
That’s not choreography. That’s physiology.
What eccentric training is (and why coaches obsess over it)
Eccentric muscle actions occur when force is produced while the muscle is lengthening—think hamstrings controlling a forward hinge, quads controlling a descent, lats controlling the return of a pull.
In research, eccentric-focused training is consistently associated with meaningful performance and tissue benefits, including improvements in strength and athletic qualities like sprinting, jumping, and change-of-direction performance.
In rehab and tendon health contexts, eccentric exercise is also a well-established loading strategy—particularly in Achilles tendinopathy, where a systematic review and meta-analysis found eccentric exercise effective for improving pain and disability/function measures compared with other exercise approaches in included trials.
Two practical takeaways:
- Eccentrics are potent. They can create a strong training stimulus even without maximal loads.
- Eccentrics require control. Done poorly, they become momentum, joint shear, and compensation.
That’s exactly where Classical Pilates shines.
Classical Pilates is spring-based eccentric training—by design
In weight training, people often “cheat” the eccentric: they drop the weight, bounce, or rush through the lowering phase. In Classical Pilates, the apparatus is built to punish that behavior:
- Springs store energy and pull you back.
- The pilates apparatus doesn’t care if you’re tired; it will return unless you resist it.
- The straps will slack, snap, or tug your alignment if you lose control.
So the method demands what most gym programs hope people do: slow, deliberate eccentric control—especially during the phase Pilates teachers often cue as “closing the springs with control.”
This matters because the eccentric phase is where many of the “real-world” skills live: deceleration, joint centration under load, and controlling end ranges without collapsing.
“Close the springs” is not a vibe. It is a strength skill.
When you “close the springs,” you are training:
1) Deceleration strength (the strength that prevents injury)
Life is mostly deceleration: stairs down, getting into a chair, catching yourself, absorbing impact, changing direction. Eccentric training improves qualities related to slowing down and controlling movement, which is why it’s heavily used in performance programming.
2) Tendon and connective tissue loading (when appropriately progressed)
Tendons respond to loading, but they require adequate stimulus and time. Reviews discussing tendon adaptations highlight that changes can occur, but outcomes vary based on loading dose and program design.
For Achilles-specific issues, eccentric exercise has demonstrated clinical benefit in a meta-analysis for mid-portion Achilles tendinopathy.
3) Hypertrophy and strength outcomes comparable to “traditional” lifting.
The point for Pilates clients: you do not need chaotic, high-impact training to create meaningful strength stimulus—especially when the eccentric is taken seriously.
What studies say about springs and Pilates resistance
Pilates isn’t just “light toning.” Changing spring conditions changes muscular demands and stability requirements.
- Studies have shown that modifying Reformer spring resistance/platform conditions can meaningfully affect core muscle activation during exercises.
- Research also demonstrates that different spring intensities can change shoulder girdle muscle activity patterns in Pilates-based movements.
- EMG research comparing Pilates exercises across apparatus has even separated muscle activity into concentric and eccentric phases—reinforcing that both phases are present and measurable in Pilates programming.
Translation: springs are not “assistance.” Springs are resistance with feedback—and the feedback is loudest on the eccentric.
The internet loves to say Pilates “isn’t enough.” But what people usually mean is: they aren’t seeing progressive resistance and controlled eccentrics.
Classical Pilates—done as designed—checks those boxes:
- Springs create scalable resistance.
- The return phase forces eccentric control.
- Precision and alignment keep the load where it belongs.
When you truly close the springs with control, Pilates stops being “movement class” and becomes what it has always been: strength training with an uncompromising standard.
References:
- Eccentric resistance training and performance outcomes (systematic review):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10185653/ - Eccentric vs concentric muscle actions on hypertrophy (healthy adults):
https://pubmed.ncbi.nlm.nih.gov/39652733/ - Eccentric exercise for mid-portion Achilles tendinopathy (meta-analysis):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9878810/ - Tendon adaptations and eccentric exercise (review – dose/threshold considerations):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7739434/ - Eccentric exercise acute and chronic effects (physiology review):
https://journals.physiology.org/doi/full/10.1152/japplphysiol.01044.2013 - Pilates Reformer spring/platform effects on core muscle activity:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11641042/ - Pilates spring resistance and shoulder girdle muscle activity:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11857265/ - Pilates EMG research separating concentric/eccentric phases:
https://www.sciencedirect.com/science/article/abs/pii/S1050641114001333
