Research library · Every source linked

Clinical Studies on Penis Extenders

What published research says about penile traction, one study at a time. Every number comes from the paper itself, with a link you can check.

1.2 to 2.3 cmaverage length gain in the 3 size studies (about 0.5 to 0.9 in)
4 to 9 hof wear a day in those studies
3 to 6 moof daily wear before the results
15studies, reviews and guidelines on this page
Read the short answer → See every source

By the Epic Extender team. We sell extenders, so every source links to the free abstract and the journal for you to check. This page is for education and is not medical advice.

The short answer

Do penis extenders work

Small clinical studies say yes, for length, when men wear one for hours a day over months. Here is what they found.

01YesTraction added length in every size study. Average gains were 1.2 to 2.3 cm (about 0.5 to 0.9 in) after 3 to 6 months.
024 to 9 ha day is what the size studies used. Shorter daily sessions of 30 to 90 minutes also added length in medical trials.
031.5 cmwas added in a randomized trial of 110 men with a curve, against 0 cm in men who did not use traction.
04Lengthis what traction changes. None of the size studies found a change in girth.
053 to 6 mois how long gains held after men stopped, in the studies that kept measuring. None followed men for years.
06Smallis the honest word for this research. The size studies had no control group, and reviews rate the evidence as low quality.

01

The 3 size studies

These studies tested extenders in healthy men who wanted more length. All three found gains. All three were small and had no control group.

No control group

Gontero et al., 2009

BJU International

A pilot phase-II prospective study to test the 'efficacy' and tolerability of a penile-extender device in the treatment of 'short penis'

+1.7 cmstretchedabout 0.7 in, after 6 months
  • +2.3 cm flaccid (about 0.9 in)
  • No change in girth
Who
Men worried about a short penis
Men
15 planned. The abstract does not give the final count.
Wear
At least 4 hours a day
Study
6 months

Good to know. Men rated their results acceptable to good, except for girth. Erect length was not measured.

Free abstractJournal pagePMID 18990153
No control group

Nikoobakht et al., 2011

Journal of Sexual Medicine

Effect of penile-extender device in increasing penile size in men with shortened penis: preliminary results

+1.7 cmstretchedabout 0.7 in, after 3 months
  • +1.7 cm flaccid (about 0.7 in)
  • No change in girth at the base
Who
Men worried about a short penis, average age 26
Men
23
Wear
4 to 6 hours a day for 2 weeks, then 9 hours a day
Study
3 months

Good to know. Tension was raised step by step. Nobody was measured after they stopped.

Free abstractJournal pagePMID 20102448
No control group

Nowroozi et al., 2015

Journal of Sexual Medicine

Applying extender devices in patients with penile dysmorphophobia: assessment of tolerability, efficacy, and impact on erectile function

+1.2 cmerectabout 0.5 in, after 6 months
  • +1.3 cm stretched, +1.7 cm flaccid
  • No change in girth
  • Gains held 3 months after stopping
Who
Men worried about their size, after counseling
Men
54
Wear
4 to 6 hours a day
Study
6 months, then 3 months off

Good to know. The only size study that measured erect length. 9 of 13 men with mild erection problems had normal function by month 9.

Free abstractJournal pagePMID 25809129

Stretched or erect? Most studies measure stretched length. That is the soft penis, gently pulled to full length. It is easy to measure the same way each time. Erect length is measured during an erection, and only one size study measured it.

02

Traction for a curve

Most traction research is on Peyronie's disease, a bend caused by scar tissue. These studies measured length too, and one of them is a randomized trial.

Table 1Traction studies in men with Peyronie's disease

Swipe to see the whole table

StudyDesignMenWearCurveLength
Ziegelmann et al., 2019Journal of Urology
Free abstractJournal pagePMID 30916626
Randomized, controlled11030 to 90 minutes a day, 3 months11.7° straighter, against 1.3° more curved without it+1.5 cm stretched, against 0 cm without it. 94% of treated men gained length.
Martinez-Salamanca et al., 2014Journal of Sexual Medicine
Free abstractJournal pagePMID 24261900
Controlled, not randomized55, against 41 untreated6 months (daily hours not in the abstract)33° down to 15°. Pain dropped. Untreated men got worse.Gain not given in the abstract. Untreated men lost length.
Levine et al., 2008Journal of Sexual Medicine
Free abstractJournal pagePMID 18373527
No control group102 to 8 hours a day, 6 months51° down to 34°, a third less+0.5 to 2.0 cm stretched
Gontero et al., 2009Journal of Sexual Medicine
Free abstractJournal pagePMID 19138361
No control group15 plannedAt least 5 hours a day, 6 months31° to 27°, not a clear change+1.3 cm stretched, still there at month 12

Numbers as reported in each abstract. Curve is measured in degrees during an erection. "Stretched" is soft length, gently pulled.

What the reviews say. A 2023 review pooled 5 studies with 419 men (Almsaoud et al.). The curve improvement held up. The pooled length change was not a clear result. European experts call traction a valid option for a curve, but say the evidence is not strong enough for a firm recommendation. If you have a curve, see a urologist first. Read our guide to extenders for Peyronie's disease.

03

Traction after prostate surgery

Doctors also test traction on men who lost length after prostate removal. A randomized trial found that short daily sessions made a clear difference.

Randomized, controlled

Toussi et al., 2021

Journal of Urology

Efficacy of a Novel Penile Traction Device in Improving Penile Length and Erectile Function Post Prostatectomy: Results from a Single-Center Randomized, Controlled Trial

Who
Men after prostate removal
Men
82
Wear
30 minutes, 1 to 2 times a day (from the trial registry)
Study
6 months

Good to know. Prostate surgery often shortens the penis. This trial tested traction to protect and restore length, not to enlarge a healthy penis.

+1.6 cmstretchedagainst +0.3 cm without traction, at 6 months
  • Erection scores held steady, while men without traction dropped
  • 87% said they would do it again
Free abstractJournal pagePMID 34060339

04

Do the gains last

Two studies kept measuring men after they stopped wearing the device. In both, the length held.

Nowroozi et al., 2015

Erect, stretched and flaccid gains did not drop in the 3 months after men stopped.

Free abstractJournal pagePMID 25809129

Gontero et al., 2009, Peyronie's

Stretched length gains were still there at month 12, 6 months after men stopped.

Free abstractJournal pagePMID 19138361

No study has followed men for years. The honest answer is that gains held for as long as the studies kept measuring, 3 to 6 months after stopping.

05

What reviews and guidelines say

Reviews pool many studies and judge how strong they are. They agree on two things. Traction adds some length, and the studies are too small to be sure how much.

Review

The only non-surgical method with evidence

This review looked at every non-surgical way to lengthen the penis. Extenders were the only one with research behind them. Their results did not look worse than surgery.

Oderda and Gontero, 2011, BJU International

Free abstractJournal pagePMID 20868389

Systematic review, 17 studies

Real gains, under 2 cm

Extenders added flaccid length, but under 2 cm. The reviewers rated the quality of the studies as poor.

Marra et al., 2020, Sexual Medicine Reviews

Free abstractJournal pagePMID 31027932

Systematic review, 57 studies

Safe and mostly effective

Non-surgical options, traction included, were safe and mostly worked. The evidence was too weak for formal recommendations.

Romero-Otero et al., 2021, BJU International

Free abstractJournal pagePMID 32575166

European guideline

Acceptable outcomes

The European urology guideline on penis size says acceptable outcomes have been reported for penile traction.

Falcone et al., 2024, European Urology Focus

Free abstractJournal pagePMID 37709592

Expert statement, Peyronie's

A valid option for a curve

Across 5 studies, stretched length rose 0.8 to 1.8 cm. The experts called traction a valid option, but said the evidence is not strong enough for a firm recommendation.

Garcia-Gomez et al., 2021, Sexual Medicine

Free abstractJournal pagePMID 34273788

US guideline, Peyronie's

No US recommendation yet

The American Urological Association guideline on Peyronie's disease does not recommend for or against traction. It notes 3 small studies that found the curve improved.

American Urological Association, 2015

Read the guideline

06

How our app data compares

Men log their training and measurements in our PE Trainer app. When we compared their results to the studies, the pattern matched. More hours brought more length.

In the size studies

4 to 9 h

of wear a day, for 3 to 6 months

1.2 to 2.3 cm

average length gain

In our app

250+ h

of traction logged in total

+1.4 cm

typical gain (+0.55 in), 81 men

90% of the men who logged 250 or more hours measured longer. Only 5% of men who logged traction got that far. Our data is self-reported, with no control group.

Read the Epic Traction Report →

07

What it means for your routine

What the research suggests

  • Wear it most days. Every study used daily wear. In our app, men who trained 3 or more days a week were least likely to measure shorter (2% against 10%).
  • Build up slowly. In one study, tension went up step by step over 3 months.
  • Think in months. The size studies ran 3 to 6 months before measuring the result.
  • More hours, more length. The size studies used 4 to 9 hours a day. Daily sessions of 30 to 90 minutes also added length in the medical trials.
  • Stop if it hurts. In the trials that reported side effects, they were mild and went away. Pain, numbness or a color change means take a break.
  • See a doctor first if you have a curve, pain or erection problems.

Built for long, daily wear

The studies worked because men wore a device for hours, most days. The Epic Extender is built to make that easy. The padded silicone base and angle straps keep long wear comfortable, and the Epic Cups cut slipping so the tension stays steady.

We coach at least 1 hour a day, building to 2 to 3 hours.

Epic Extender Full Set

180-day money back guarantee

See the Epic Extender →

Questions

Penis extender research questions

Do penis extenders really work?

Small clinical studies say yes, for length. In three studies of men worried about their size, average gains were 1.2 to 2.3 cm (about 0.5 to 0.9 inches) after 3 to 6 months of daily wear. None of these studies had a control group, so the evidence is promising but not strong.

How much length can a penis extender add?

In the size studies, average gains were 1.3 to 1.7 cm stretched (about half an inch) and 1.7 to 2.3 cm flaccid. The one study that measured erect length found 1.2 cm. Results vary from man to man.

How many hours a day do you need to wear an extender?

The size studies used 4 to 9 hours a day. Trials in men with a curve or after prostate surgery found gains with 30 to 90 minutes a day. In our app data, training on more days mattered more than very long days. We coach at least 1 hour a day, building to 2 to 3 hours.

Are penis extender gains permanent?

Small studies that kept measuring men after they stopped found the length held for the 3 to 6 months they were followed. No study has followed men for years.

Do penis extenders increase girth?

No. None of the size studies found a change in girth. Traction adds length. In our app data, girth gains came from pumping, not from extending.

Do doctors use penile traction?

Yes. Urologists study traction for Peyronie's disease and after prostate surgery, and randomized trials found length gains in both. Guidelines have not made a firm recommendation yet, because the studies are small.

Are penis extenders safe?

Reviews call traction safe. In the trials that reported side effects, they were mild and went away. Stop if you feel pain or numbness or see a color change, and see a doctor if it does not settle.

What is the difference between stretched and erect length?

Stretched length is measured on the soft penis, gently pulled to full length. Most studies use it because it is easy to repeat. Erect length is measured during an erection. Only one size study measured it, and found 1.2 cm after 6 months.

Sources

Every study on this page

How we checked them. We opened each paper's abstract or free full text and took every number from the paper itself, not from a blog or a summary. Where an abstract does not give a number, we say so. Each source links to its free abstract on Europe PMC, a public research library that mirrors PubMed, and to the journal's own page.

  1. Gontero P, Di Marco M, Giubilei G, et al. (2009). A pilot phase-II prospective study to test the 'efficacy' and tolerability of a penile-extender device in the treatment of 'short penis'. BJU International, 103(6):793-797.

    Free abstractJournal pagePMID 18990153

  2. Nikoobakht M, Shahnazari A, Rezaeidanesh M, et al. (2011). Effect of penile-extender device in increasing penile size in men with shortened penis: preliminary results. Journal of Sexual Medicine, 8(11):3188-3192.

    Free abstractJournal pagePMID 20102448

  3. Nowroozi MR, Amini E, Ayati M, et al. (2015). Applying extender devices in patients with penile dysmorphophobia: assessment of tolerability, efficacy, and impact on erectile function. Journal of Sexual Medicine, 12(5):1242-1247.

    Free abstractJournal pagePMID 25809129

  4. Ziegelmann M, Savage J, Toussi A, et al. (2019). Outcomes of a Novel Penile Traction Device in Men with Peyronie's Disease: A Randomized, Single-Blind, Controlled Trial. Journal of Urology, 202(3):599-610.

    Free abstractJournal pagePMID 30916626

  5. Martinez-Salamanca JI, Egui A, Moncada I, et al. (2014). Acute phase Peyronie's disease management with traction device: a nonrandomized prospective controlled trial with ultrasound correlation. Journal of Sexual Medicine, 11(2):506-515.

    Free abstractJournal pagePMID 24261900

  6. Levine LA, Newell M, Taylor FL (2008). Penile traction therapy for treatment of Peyronie's disease: a single-center pilot study. Journal of Sexual Medicine, 5(6):1468-1473.

    Free abstractJournal pagePMID 18373527

  7. Gontero P, Di Marco M, Giubilei G, et al. (2009). Use of penile extender device in the treatment of penile curvature as a result of Peyronie's disease. Results of a phase II prospective study. Journal of Sexual Medicine, 6(2):558-566.

    Free abstractJournal pagePMID 19138361

  8. Almsaoud NA, Safar O, Alshahrani ST, et al. (2023). The effect of penile traction device in men with Peyronie's disease on penile curvature, penile length, and erectile dysfunction: a systematic review and meta-analysis. Translational Andrology and Urology, 12(11):1673-1685.

    Free abstractJournal pagePMID 38106680

  9. Toussi A, Ziegelmann M, Yang D, et al. (2021). Efficacy of a Novel Penile Traction Device in Improving Penile Length and Erectile Function Post Prostatectomy: Results from a Single-Center Randomized, Controlled Trial. Journal of Urology, 206(2):416-426.

    Free abstractJournal pagePMID 34060339

  10. Oderda M, Gontero P (2011). Non-invasive methods of penile lengthening: fact or fiction? BJU International, 107(8):1278-1282.

    Free abstractJournal pagePMID 20868389

  11. Marra G, Drury A, Tran L, et al. (2020). Systematic Review of Surgical and Nonsurgical Interventions in Normal Men Complaining of Small Penis Size. Sexual Medicine Reviews, 8(1):158-180.

    Free abstractJournal pagePMID 31027932

  12. Romero-Otero J, Manfredi C, Ralph D, et al. (2021). Non-invasive and surgical penile enhancement interventions for aesthetic or therapeutic purposes: a systematic review. BJU International, 127(3):269-291.

    Free abstractJournal pagePMID 32575166

  13. Falcone M, Bettocchi C, Carvalho J, et al. (2024). European Association of Urology Guidelines on Penile Size Abnormalities and Dysmorphophobia: Summary of the 2023 Guidelines. European Urology Focus, 10(3):432-441.

    Free abstractJournal pagePMID 37709592

  14. Garcia-Gomez B, Aversa A, Alonso-Isa M, et al. (2021). The Use of Penile Traction Devices for Peyronie's Disease: Position Statements from the European Society for Sexual Medicine. Sexual Medicine, 9(4):100387.

    Free abstractJournal pagePMID 34273788

  15. American Urological Association. (2015). Peyronie's Disease: AUA Guideline.

    Read the guideline

Keep reading

The Epic Traction Report → The best penis extenders → Extenders for Peyronie's disease → Penis extender before and after photos → Before and after results →

This page summarizes published research for education. It is not medical advice. Our products are not intended to diagnose, treat, cure, or prevent any disease and have not been evaluated by the FDA. Results vary. Consult your doctor if you have a medical condition.