Français
Testicular thermal contraception
What if your body was the solution all along?
The thermal method has been around for forty years. No hormones, no surgery, and you can check for yourself whether it's working, with a lab test or at home. Yet hardly anyone has heard of it, even here in France.
The project
For now, the thermal method is still experimental. Yet the results are striking: it's effective, reversible, and its side effects are minor compared with the more common contraceptive methods. We're a community of people who use it, and we're the ones exploring it and working out how it works.
For a teenage girl, booking an appointment to talk about contraception is almost a rite of passage. For men, it's the exception. There's a logic to people who can get pregnant being in charge of their own safety: it's their body on the line. The gap is still huge, and it's no secret. Otoko works to get men involved in turning that around.
It doesn't flow down from an institution to its users. It travels peer to peer, through workshops and talking circles, and the people who take it up shape it in turn. Designs, protocols, and resources are published under a free license, and collectives run their own workshops in France, Belgium, Germany, and Canada without asking Otoko for anything.
Bringing your sperm concentration down and building trust with your partner are two different things. The first one can be measured. The second one has to be built, and nothing measures it, even though it's the one that decides everything. Otoko supports both, and puts you in touch with healthcare professionals trained in the method, mostly in France.
Research
There's little clinical data so far, and the protocols written in the 1980s aren't as robust as today's. So the current research can't settle every question. Otoko gathers the studies and grades them by level of evidence, runs a follow-up survey with the people who use the method, and measures and documents the rings. Producing this data is part of the work, not something to wait for first.
The studies, in the English guideThe method
No hormones. Reversible. You can check it with a lab test or at home.
Sperm is produced in the testicles, a few degrees below body temperature. When the lower part of the ring is pulled back toward the perineum, the testicles rise into the inguinal canals and stay held there. Developing sperm don't survive at that temperature.
The documented protocol is to keep the testicles lifted at least 15 hours a day, every day, during waking hours. A single day off is enough for the effect to no longer be guaranteed. Sperm production stops within the first few days, but contraception only counts as reached after about three months, and only if two tests show it: fewer than 1 million motile sperm per milliliter, on two semen analyses three weeks apart. (Soufir and Mieusset 2012, practical guide, protocol described for briefs.) In the founding Toulouse study, that threshold was reached in 3.5 months on average. (Mieusset and Bujan 1994, 9 couples.)
Keep another method until those two analyses. After that, the follow-up goes on: one semen analysis a month until month six, then one every two months. (Soufir and Mieusset 2012.)
A contraceptive method is never just a device. What makes thermal contraception work is a protocol: understanding what's happening with your fertility, knowing how to check it, knowing how to wear the ring, and knowing how to talk about it as a couple. That last part is the one no instructions ever cover.
The ring doesn't heat up, and it does nothing to fertility by itself. It holds the testicles up, and body heat is what stops sperm production. Rings and jockstraps are tools for testicular elevation: they have no proven contraceptive properties, and they're best thought of as underwear or simple penis rings, made for everyday wear. No trial has ever looked at the silicone ring. (Baron 2025.)
The protocol is what makes the contraception, and semen analyses are what confirm it. Until your concentration is below the threshold on two analyses three weeks apart, keep another method.
In practice
The step people miss most often is pulling the ring back toward the perineum. That's the move that lifts the testicles and keeps them up: without it, the ring stays in place but wearing it does nothing. If in doubt, that's the one to redo.
Start with the middle sizes of the kit. Wash the rings with soap before each use. At the start, the testicles are in the scrotum, hanging low.
If you have to pull really hard to get the ring on, the size is too small.
Hold the penis in one hand and pull it upward. With the other hand, position the ring, held open between your fingers.
Slide the ring down to the base of the penis, until it touches the scrotum.
Pull the penis upward with one hand, and with the other, stretch the ring downward. The hand holding the penis then gently brings the skin of the scrotum through the ring. The penis and the scrotal skin go through, and the testicles stay on the body side.
This often takes a few tries at first, and you can start over as many times as you need.
This is the most important step, and the one people miss most often. Take the lower part of the ring and pull it back, toward the perineum. The testicles then rise into the inguinal canals, inside the body, and the ring settles behind the scrotum, as close to the body as possible. The testicles stay on the body side and never go through the ring.
Without this step, the ring stays in place but the testicles drop back down, and wearing it does nothing.
Four similar moves settle the ring against the body. Pull the penis to the right and the ring to the left, then the other way around. Or pull the penis down and settle the ring closer to the pubic bone and the skin. These moves improve the hold and the lift.
The testicles sit above the upper part of the ring. If they don't, don't panic: the position gets better with time and practice. The higher the testicles, the more effective it is.
If you're not sure about the lift, redo step 5: pull the lower part of the ring toward the perineum.
Once the ring is on, tug on it gently: it should stay where it is. A few squats or small jumps let you check it while you move. The ring should stay put without slipping on its own.
If the ring slips on its own, or the testicles drop back down or slip back through, the hold isn't right and the size is too big.
Take the lower part of the ring and pull it outward. The testicles drop back down, and the ring comes off easily.
When you pee, take the ring off, or at least loosen its lower part.
Illustrations by May. The same drawings make up the ring guide handed out at workshops. The full practical guide, in English.
Get started
It all starts with a conversation. Everything else gets decided afterward, and nothing happens without it. Not sure which one fits you? The Start page helps you choose in two questions.
One hour with Sam on a video call, in English, pay what you can. How the body works, the scientific sources, the protocol step by step, everyday life with the ring, and the agreement to work out with your partner or partners.
Three hours in a group: in Pantin, pay what you can, or with a collective elsewhere in France, at its own price. You make your own silicone rings, try on sizes until you find the right one, and meet other people who use the method.
Independent collectives run their own workshops and talking circles with Otoko's open resources, mostly in France. The map lists them, along with healthcare professionals who follow the method.
A semen analysis is what tells you whether you're below the threshold, and a healthcare professional is the person who follows you through it. Without that follow-up there's no contraception, just a ring you're wearing. The map lists doctors, midwives, and urologists who know the thermal method, mostly in France. Outside France, a doctor near you is the place to start.
Open source
Protocols, science, testimonials, workshop materials. The content and the tools are published under the free Creative Commons CC BY 4.0 license, which means any collective can reuse them without asking.
Good to know