The Contraction-Relaxation Cycle, the Key to Facial Movement
Medically reviewed by
4 independent reviewers
Andrew Conrad Barile, PT, DPT
Doctor of Physical Therapy (DPT) | Licensed Physical Therapist (PT) | CEO and Founder, Xtreem Pulse LLC
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Dr. Andrew Conrad Barile is a Doctor of Physical Therapy and the CEO and Founder of Xtreem Pulse LLC, the engineering company behind PureLift. He earned his Doctorate in Physical Therapy from Daemen College and is a licensed physical therapist.
He brings over two decades of clinical and entrepreneurial experience across physical therapy, craniosacral therapy and medical device innovation, built on a working knowledge of human anatomy and muscle physiology.
For PureLift LAB he reviews how current is delivered across all ten levels, from sub-sensory nanocurrent and skin-level microcurrent to motor-level EMS, and how the Infuse pass fits into the same ten-minute routine.
Bertica M. Rubio, M.D.
Board-Certified Physician, Dartmouth Medical School | Medical Director, Antiaging Regenerative Medicine Clinic
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Dr. Bertica M. Rubio is a board-certified physician and Medical Director of the Antiaging Regenerative Medicine Clinic in Redlands, California. She earned her Doctor of Medicine from Dartmouth Medical School and completed her pediatrics residency at UC Irvine Medical Center.
With decades of clinical experience, she specialises in age management medicine, regenerative medicine, wound healing and growth factor therapies, and her practice integrates evidence-based medical science with advanced aesthetic treatment.
For PureLift LAB she reviews articles for medical accuracy across the whole dial, from the gentle nanocurrent and microcurrent settings through to muscle-level EMS and the Infuse pass.
Daniel Grinberg, MD, FACS
Board-Certified Otolaryngologist | Head and Neck Surgeon | Fellow, American College of Surgeons | Mount Sinai
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Daniel Grinberg, MD, FACS is a board-certified otolaryngologist and head and neck surgeon at ENT and Allergy Associates in West Nyack, New York. He earned his medical degree from Columbia University College of Physicians and Surgeons.
He completed his otolaryngology residency at New York University Medical Center, serves as Assistant Clinical Professor at Mount Sinai School of Medicine, and is a Fellow of both the American College of Surgeons and the American Academy of Otolaryngology.
For PureLift LAB he brings a wider clinical lens, connecting at-home facial stimulation from microcurrent to EMS to the anatomy underneath, with the same rigour we apply to every device specification.
Prof. Dr. med. Ivo Buschmann
Chair of Angiology, Medizinische Hochschule Brandenburg | Clinic Director, University Clinic for Angiology
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Prof. Dr. med. Ivo Buschmann is Chair of Angiology at the Medizinische Hochschule Brandenburg Theodor Fontane and Clinic Director of the University Clinic for Angiology at the Brandenburg University Hospital.
He trained at the University of Hamburg, was a Max Planck Society Fellow at the Max Planck Institute for Heart and Lung Research, and held senior consultant posts at the Charite Universitatsmedizin Berlin before his appointment as Chair in 2016.
One of Europe's leading authorities on arteriogenesis, with over 150 peer-reviewed publications and US and EU patents, he reviews for PureLift LAB how the evidence on electrical stimulation is read and where its limits lie.
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A muscle does not simply switch on, it contracts and releases in a cycle, and the release half is doing as much work as the squeeze.
This article explains the cycle and why it matters, such as:
- What actually happens when a muscle fires
- Why the relaxation half is not wasted time
- Why moving the device too fast costs you contractions
- What the cycle does for circulation
- How to work with the rhythm rather than against it
and many more!
By the end you will understand why pace matters more than pressure.
Key Points:
A muscle contracts when its nerve fires and releases when the signal stops, and both halves are part of one cycle.
The release lets blood move through the muscle again, which is where the post-session flush comes from.
Move the device too quickly and cycles are cut short, so you get fewer complete contractions in the same three minutes.
A few seconds of sustained contact in each position is what lets a cycle complete.
Pace is the technique variable most people get wrong, and it costs more than the dial setting does.
The rhythmic squeeze you feel from level 3 upwards is not a continuous pull, it is a repeating cycle, and understanding it changes how you run a session.
What happens when a muscle fires
A muscle contracts when the nerve that drives it receives an electrical signal, and it releases when that signal stops.
An EMS device delivers that signal in a pattern rather than continuously, so the muscle is being asked to work and then let go, over and over.
A review of kilohertz-frequency stimulation describes three separate thresholds in everyone, the point you feel the current, the point the muscle moves, and the point it hurts (Ward 2009), and the cycle only happens above the second one.
Below it, at levels 1 and 2, there is no cycle because there is no contraction, which is why those settings feel completely different.
Why the release matters
A contracted muscle compresses the small vessels running through it, which restricts blood flow while the squeeze is held.
When the muscle releases, blood moves through again, and it is the repetition of that squeeze-and-release that moves blood around the area.
So the flush and fresher look after a session comes from the cycle rather than from the contraction alone, and a device that simply held a muscle tight would not produce it.
It is the same reason walking does more for circulation than standing still while tensing your legs.
Why pace decides your session
Each cycle takes time, and if you move the device on before a cycle completes, that contraction is cut short.
Glide quickly across your face and you may get through the whole area in three minutes while delivering a fraction of the complete contractions you could have.
The fix is to move slowly, giving each position a few seconds of sustained contact before moving on.
This is the technique error that costs the most and gets discussed the least, because it does not feel like an error, it feels like being efficient.
Working with the rhythm
Settle the device in one position, let the cycle happen a few times, then move a short distance and repeat.
Keep enough pressure to maintain full contact and no more, since pressing harder does not lengthen a cycle and pressing into bone adds nothing.
Watch the mirror rather than the clock, because seeing the muscle answer confirms that a complete cycle is happening.
If the rhythm feels jerky or inconsistent, that is usually contact rather than the device, so add serum before you touch the level.
Why the signal keeps changing
Repeating an identical cycle for ten minutes lets both the muscle and the nerves driving it get used to the pattern, so the session fades even though the output has not changed.
PDM, the delivery architecture inside every PureLift, moves the signal across 361 frequency points between 1,370 and 1,730 Hz so it does not repeat, varying frequency only and leaving amplitude exactly where you set it.
Pooling 22 studies, researchers found that stimulation which keeps changing produced more evoked force with less fatigue than a fixed pattern (Cavalcante 2026), and a randomised crossover trial found that varying the frequency reduced how quickly people habituated to it (Avendano-Coy 2019).
Not every study agrees (Papaiordanidou 2014), so the design goal is to reduce accommodation and we never claim your muscles cannot adapt.
What repeated cycles build over time
Around forty small muscles sit under the skin of your face, held inside a connected sheet called the SMAS, and engaging them repeatedly is how EMS supports a firmer, more defined look along the jaw, cheeks and neck with continued use.
In the largest facial trial of its kind, 108 women used daily muscle stimulation for twelve weeks and ultrasound measured an 18.6 percent increase in cheek-muscle thickness, with a clear difference from the untreated group at six weeks (Kavanagh 2012), and a double-blind sham-controlled trial in adults over 65 found muscle thickness and bite force increased after six weeks (Chang 2020).
Those are category studies run with their own devices, so they show what facial muscle stimulation can do rather than what any product does for you.
The point for this article is that the cumulative change comes from accumulated complete cycles, which is why pace is not a detail.
What the cycle does not do
It does not drain fluid in any medical sense, since no consumer facial device has been shown to clear a measured volume of anything.
It does not fill a crease or replace lost volume, because the muscle sits beneath the skin rather than in it.
It does not work at levels 1 and 2, where there is no contraction to cycle.
Model notes
All five PureLift models run nanocurrent at level 1, microcurrent at level 2, EMS from level 3 to 10, and Infuse as a second pass, so the cycle described here happens from level 3 upwards on any of them.
The session is three minutes on each side of the face at a level where you can see the muscle answer, followed by the Infuse pass, about ten minutes in total.
Face at $499 and Pro at $699 reach up to 7 milliamps, Pro Edition at $799 reaches up to 7.7, and Pro Plus + at $899 and GLOW at $999 reach up to 9, all measured at 500 ohms and always written as up to.
GLOW alone adds light, red at 634 nm cleared for the treatment of wrinkles, blue at 465 nm cleared for mild-to-moderate inflammatory acne, and purple, which is red and blue running together.
Every model is cleared through the FDA 510(k) pathway, under records K190269 for Face, K230506 for Pro and Pro Edition, K221443 for Pro Plus + and K243587 for GLOW, and all five are made in Japan in an ISO 13485 facility.
Anyone with a pacemaker or another implanted electronic device, anyone pregnant, and anyone with epilepsy or a seizure disorder should not use the device at all.
For what each level feels like, read what EMS feels like, and for the anatomy, read facial muscle anatomy.
Model figures verified on 9 September 2026 against the PureLift LAB store and FDA records K190269, K230506, K221443 and K243587. Every model runs nanocurrent, microcurrent, EMS and Infuse; consumer copy always says up to.
Two related questions come up often alongside this one, and we have answered both in full: whether these devices work at all, and what a microcurrent device actually does to your face.