Evidence summary by condition

• Johnson MI, Paley CA, Jones G, Mulvey MR, Wittkopf PG. BMJ Open, 2022

  Meta-analysis381 randomised trials, 24,532 participants

  Finding. TENS produced a clinically worthwhile reduction in pain intensity compared with placebo during or immediately after stimulation, with moderate-certainty evidence and no serious adverse events.

  Applicability. Pooled conventional TENS at a strong but comfortable level — the same dose principle these pods use, though delivered by clinic-grade stimulators.

• Gibson W, Wand BM, Meads C, Catley MJ, O'Connell NE. Cochrane Database of Systematic Reviews, 2019

  Cochrane reviewOverview of 8 Cochrane reviews, 51 trials

  Finding. Evidence across chronic pain conditions was judged low or very low certainty, mostly because trials were small and short; the review could neither confirm nor rule out worthwhile benefit.

  Applicability. A deliberate counterweight to the pooled result above: relief is real for many users but the evidence base is fragile.

• Vance CGT, Dailey DL, Rakel BA, Sluka KA. Pain Management, 2014

  Systematic reviewMechanistic and clinical review

  Finding. Adequate stimulation intensity and correct electrode placement determine whether TENS works; under-dosing explains many negative trials.

  Applicability. Directly why this app caps but does not hide the level, and shows a pad-placement map for every body area.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Recommended.

• Chen L-X, Zhou Z-R, Li Y-L, et al. Clinical Journal of Pain, 2016

  Meta-analysis27 randomised trials

  Finding. TENS reduced knee osteoarthritis pain versus control, with high heterogeneity between studies and short follow-up.

  Applicability. Supports symptomatic use alongside, not instead of, exercise therapy.

• Rutjes AWS, Nüesch E, Sterchi R, et al. Cochrane Database of Systematic Reviews, 2009

  Cochrane review18 small trials, 813 participants

  Finding. Evidence was inconclusive because of small samples and poor trial quality; no reliable estimate of benefit could be given.

  Applicability. The reason this use is graded conditional rather than recommended, despite the later meta-analysis.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise
• Relief typically fades within hours of switching off

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot
• A total knee replacement with pads placed directly over the surgical scar before it has fully healed

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Conditional — may help.

• Khadilkar A, Odebiyi DO, Brosseau L, Wells GA. Cochrane Database of Systematic Reviews, 2008

  Cochrane review4 randomised trials, 585 participants

  Finding. No consistent evidence that TENS reduced chronic low back pain or disability compared with placebo.

  Applicability. Applies directly to home use for this indication.

• Qaseem A, Wilt TJ, McLean RM, Forciea MA. Annals of Internal Medicine, 2017

  Systematic reviewAmerican College of Physicians guideline review

  Finding. TENS was not recommended for chronic low back pain; exercise, multidisciplinary rehabilitation and self-care were preferred.

  Applicability. Why the app frames this as an optional comfort adjunct beside movement and heat.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot
• New back pain with leg weakness, numbness in the saddle area or loss of bladder or bowel control — seek urgent care instead

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Insufficient evidence.

• Martimbianco ALC, Porfírio GJ, Pacheco RL, Torloni MR, Riera R. Cochrane Database of Systematic Reviews, 2019

  Cochrane review7 randomised trials, 651 participants

  Finding. Very low certainty evidence that TENS reduces chronic neck pain; the review could not draw firm conclusions.

  Applicability. Caps the claim at symptomatic comfort, not correction of posture or strain.

• Kroeling P, Gross A, Graham N, et al. Cochrane Database of Systematic Reviews, 2013

  Cochrane review20 trials of electrotherapy for neck pain

  Finding. Low quality evidence suggested TENS may be more effective than placebo for chronic neck pain immediately after treatment.

  Applicability. Short-term relief only; no evidence of lasting change.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise
• Light-headedness if pads sit too high on the neck — move them down and lower the level

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Conditional — may help.

• Kim K-M, Croy T, Hertel J, Saliba S. Journal of Orthopaedic & Sports Physical Therapy, 2010

  Systematic review8 randomised trials after knee surgery

  Finding. NMES combined with exercise improved quadriceps strength more than exercise alone.

  Applicability. Achieved with clinical stimulators producing measured, visible contractions — not equivalent to a snap-on wellness pod.

• Stevens-Lapsley JE, Balter JE, Wolfe P, Eckhoff DG, Kohrt WM. Physical Therapy, 2012

  RCT66 participants after total knee arthroplasty

  Finding. Early NMES added to rehabilitation improved strength and functional performance at 3.5 weeks.

  Applicability. Started in supervised rehabilitation, with dose progressed by a therapist.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise
• Pain or swelling around a fresh surgical site if the contraction is too strong

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot
• Pads over an unhealed incision, staples or a dressing
• Any use not agreed with the surgeon or treating therapist

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Conditional — may help.

• Jin DM, Xu Y, Geng DF, Yan TB. Diabetes Research and Clinical Practice, 2010

  Meta-analysis3 randomised trials, 78 participants

  Finding. Electrical nerve stimulation reduced painful diabetic neuropathy symptoms at 4 and 6 weeks compared with sham.

  Applicability. Very small pooled sample; supports a supervised trial of therapy, not a general claim.

• Dubinsky RM, Miyasaki J. Neurology (AAN evidence report), 2010

  Systematic reviewAAN assessment of TENS for neurological pain

  Finding. TENS was rated probably effective for painful diabetic neuropathy (Level B) and not recommended for chronic low back pain.

  Applicability. The strongest formal statement available for this indication.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise
• Unnoticed burn or pressure injury on skin with reduced sensation

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot
• Any open ulcer, blister, callus breakdown or infection on the foot
• Use without a daily skin inspection, or without clinician agreement

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Conditional — may help.

• Martimbianco ALC, Porfírio GJ, Pacheco RL, Torloni MR, Riera R. Cochrane Database of Systematic Reviews, 2019

  Cochrane review7 randomised trials, 651 participants

  Finding. Very low certainty evidence of pain reduction in chronic neck pain; osteoarthritis was not analysed separately.

  Applicability. The grade is borrowed from chronic neck pain, which is why it stays investigational here.

• Escortell-Mayor E, Riesgo-Fuertes R, Garrido-Elustondo S, et al. Manual Therapy, 2011

  RCT90 participants with mechanical neck pain

  Finding. TENS and manual therapy both reduced pain, with no clear advantage for either at six months.

  Applicability. Supports pairing the pods with hands-on or exercise therapy rather than replacing it.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise
• Headache or dizziness — stop the session and reduce the level or move the pads lower

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot
• Any pad on the front or sides of the neck, over the throat, thyroid or carotid pulse
• Neck pain after trauma, or with arm weakness, clumsy hands or unsteady walking — needs assessment first

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Conditional — may help.

• Babault N, Cometti C, Maffiuletti NA, Deley G. European Journal of Applied Physiology, 2011

  Systematic reviewReview of electrical stimulation in athletes

  Finding. Recovery benefits were inconsistent and often no better than passive rest or active recovery.

  Applicability. Directly relevant to home use after exercise.

• Malone JK, Blake C, Caulfield BM. Journal of Strength and Conditioning Research, 2014

  Systematic review17 studies of neuromuscular stimulation for recovery

  Finding. Some reduction in perceived soreness, with little effect on objective performance measures.

  Applicability. Perceived comfort is the only outcome supported.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot
• Severe, one-sided or worsening muscle pain with dark urine — seek care rather than stimulating

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Insufficient evidence.

• Porcari JP, Miller J, Cornwell K, et al. Journal of Sports Science and Medicine, 2005

  RCT24 participants, 8 weeks of abdominal stimulation

  Finding. No significant change in body weight, body fat percentage or waist girth versus control, despite reported subjective firmness.

  Applicability. The closest study to the marketing claim, and it does not support it.

• US Food and Drug Administration consumer update on electrical muscle stimulators

  Systematic reviewRegulatory position

  Finding. Stimulators may temporarily strengthen or tone a muscle, but claims of weight loss, girth reduction or fat removal are not supported.

  Applicability. Sets the ceiling on what this mode may be described as doing.

• Skin redness or itch under the pads — the commonest effect, usually settling within hours
• Contact dermatitis from the adhesive with repeated use on the same spot
• A stinging or burning feeling if the level is set too high, or if a pad is dry, curled or reused past its life
• Muscle ache after EMS modes, similar to after exercise
• Cramping or nausea if the abdominal contraction is set too strong

• A pacemaker, implanted defibrillator, neurostimulator, insulin pump, cochlear implant or any other active implanted device
• Pads over the front or sides of the neck (carotid sinus), the eyes, the mouth or across the chest
• Pads over broken, infected, numb or recently irradiated skin
• Pregnancy, unless a clinician has agreed the site and settings
• Undiagnosed pain, suspected fracture, active cancer at the site or a suspected blood clot
• Pregnancy, a hernia, surgical mesh, or an intrauterine device with pads low on the abdomen

Electrode stimulation of this class is regulated as a powered muscle stimulator or a TENS device. It produces no radiofrequency field, so no pulsed radiofrequency clearance or evidence applies to it, and sessions record zero RF dose. Recommendation for this indication: Not recommended at home.