The SMAS Layer and What It Has to Do With a Softening Jawline
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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The SMAS is a fibrous sheet sitting between the skin and the deeper facial muscles, connecting the two so that when a muscle moves, the skin above it moves.
This article explains what is actually happening, such as:
- What the SMAS is
- What happens to it over time
- The other causes it gets blamed for
- Why surgeons talk about the SMAS
- What a device can and cannot reach
and many more!
A home device does not reach or reposition the SMAS, and we are not going to suggest it does; what it reaches is the muscle the SMAS is attached to.
Key Points:
SMAS stands for superficial musculoaponeurotic system, a sheet of fibrous tissue and muscle fibres under the skin.
It is what a surgeon tightens in a SMAS facelift, and no current tightens it.
Sagging has at least three causes and SMAS laxity is one of them, not the whole story.
EMS works the muscle the SMAS connects to, which supports the structure without repositioning it.
Anyone claiming a home device lifts the SMAS is overselling.
What the SMAS is
Superficial musculoaponeurotic system is an unwieldy name for a straightforward structure: a continuous layer of fibrous tissue and muscle fibres running through the face, sitting between the fat just under the skin and the deeper tissues.
Its function is connection. Facial muscles do not mostly attach to bone at both ends the way a bicep does; many attach into this sheet, which then attaches into the skin. That arrangement is why a facial muscle contracting produces a visible expression rather than just a movement under the surface.
In the lower face the layer continues into the platysma, the broad sheet running down the neck, which is why jawline and neck changes tend to arrive together.
What happens to it over time
The fibrous tissue loses elasticity, so the sheet stretches and stays stretched rather than recoiling. The attachments that anchor it descend. And the muscle fibres within it lose tone, like muscle anywhere.
The visible result is that the tissue it supports sits lower than it used to, which reads as a softening jawline and the appearance of jowls.
That is one cause among several, and treating it as the whole explanation is where most articles on this subject go wrong.
The other causes it gets blamed for
Fat pads in the midface lose volume and drift downward, so weight that used to sit high on the cheek now rests on the lower face. That is a volume change and no amount of SMAS discussion addresses it.
The dermis loses collagen and elastin, so the skin itself stretches. That is laxity, a change in the material rather than in the support.
Bone remodels too; the facial skeleton changes shape with age, which alters what everything above it drapes over.
Most people over forty have all four happening at once, in different proportions, which is why one intervention rarely satisfies.
Why surgeons talk about the SMAS
A facelift that pulls only skin produces a tight, pulled look because the skin is being asked to hold up a structure it was never holding. A SMAS facelift lifts and secures the supporting layer itself, so the skin is redraped rather than stretched.
That distinction is the reason the term entered popular vocabulary, and it should also be the reason nobody claims to replicate it without surgery. Repositioning a layer of tissue requires access to it.
What a device can and cannot reach
EMS crosses the motor threshold and contracts the muscle. The facial muscles that attach into the SMAS are exactly the muscles it works, so better tone in those muscles means better support within the structure.
Kavanagh and colleagues measured an 18.6 percent increase in cheek muscle thickness over 12 weeks of motor-level facial stimulation across 108 women (10.1111/jocd.12007), and Chang and colleagues ran a double-blind sham-controlled trial (10.3390/ijerph17113783). Both are category studies rather than trials of any one device, and neither was measuring the SMAS.
So the honest claim is muscle tone, and its consequence for how the supported area reads. The claim we are not making is that current tightens fibrous tissue or repositions a layer, because it does not.
Working the lower face
Work upward and outward along the jawline toward the ear rather than downward, following the direction the tissue has drifted away from.
Include the neck if your model's instructions cover it, since the platysma is continuous with the layer above and treating the jaw in isolation ignores half the structure.
Keep the skin damp with a water-based serum; a session that starts to drag means a dry patch rather than a need for more power. Three minutes per side is the maximum on any PureLift model, and the ten minute session ends on its own.
When the honest answer is a surgeon
If the tissue has descended substantially, the structural change is past what muscle tone compensates for, and a consultation tells you more than another article will.
A device is a good foundation and a poor substitute; used honestly it supports the muscle side of a problem with four sides.
For the full breakdown of which technology sits where on the dial, see how the nine PureLift technologies work.