Your testicles move upward toward your body because of a muscle called the cremaster, and in most cases it’s completely normal. This thin muscle wraps around each testicle and contracts automatically in response to cold, touch, fear, laughter, and sexual arousal, pulling the testicle up toward your groin. For some people, the muscle pulls hard enough to move a testicle all the way out of the scrotum and into the inguinal canal, the passageway in your lower abdomen that the testicle originally traveled through during development.
Why the Cremaster Muscle Exists
Sperm production requires a temperature slightly below core body temperature, which is why the testicles hang outside the body in the first place. The cremaster muscle acts as a thermostat. When you’re cold, it contracts to pull the testicles closer to the warmth of your body. When you’re warm, it relaxes and lets them drop. This is the same reason your scrotum visibly tightens in cold water and hangs loose in the heat.
Temperature regulation isn’t the muscle’s only job. During a fight-or-flight response, the cremaster contracts to tuck the testicles into a more protected position closer to the body. The same thing happens during sexual arousal. Both responses are involuntary, driven by nerve signals from the lower spine through a nerve called the genitofemoral nerve. You can even trigger the reflex by stroking or rubbing the skin on your inner thigh, which activates sensory nerves connected to the same spinal pathway.
Common Triggers for Testicular Retraction
If you’ve noticed your testicles pulling upward in specific situations, you’re likely experiencing one of these triggers:
- Cold temperatures: Swimming in cold water, stepping outside in winter, or even sitting in an air-conditioned room.
- Physical touch: Contact with the inner thigh or groin area, including during exercise when your thighs rub together.
- Emotional responses: Fear, anxiety, surprise, and even laughter can activate the reflex.
- Sexual activity: The testicles naturally draw upward during arousal and often sit very close to the body at the point of orgasm.
- Vigorous exercise: Running, cycling, and heavy lifting can all trigger cremaster contractions.
In all of these scenarios, the testicle returns to its normal position once the stimulus passes. This is how the system is designed to work.
When It’s a Retractile Testicle
Some people have a particularly strong cremaster reflex, and for them, a testicle may fully leave the scrotum and sit up in the groin for a while before dropping back down on its own or with gentle manual guidance. This is called a retractile testicle, and it has traditionally been considered a normal variant rather than a medical problem. The key characteristic: the testicle can be moved back into the scrotum without pain, and it stays there at least temporarily before the reflex pulls it up again.
Retractile testicles are more common in boys before puberty, when the cremaster reflex tends to be more active. In many cases, the issue resolves on its own as the testicle grows larger and heavier during puberty, making it harder for the muscle to pull it out of position. That said, retractile testicles also occur in adults, particularly those with a strong reflex or during intense physical activity.
Retractile vs. Undescended Testicles
The distinction between a retractile testicle and an undescended (or ascending) testicle matters because the health implications are very different. A retractile testicle moves freely between the scrotum and groin and can be guided back into place without discomfort. An undescended testicle tends to be smaller than the other one, snaps back out of the scrotum immediately when released, and causes pain when you try to move it into position.
There is one complication worth knowing about: a retractile testicle can sometimes become an ascending testicle over time, meaning it gradually stops returning to the scrotum on its own. Estimates of how often this happens vary widely, ranging from 2% to 45% depending on the study. This is why doctors sometimes recommend monitoring retractile testicles periodically rather than assuming they’ll always stay benign.
True undescended testicles that remain outside the scrotum long-term carry a roughly 3 to 5 times higher risk of testicular cancer compared to the general population. Early surgical correction (a procedure called orchiopexy, where the testicle is secured in the scrotum) roughly cuts that risk in half compared to delaying the procedure. A retractile testicle that spends most of its time in the scrotum does not carry the same elevated risk.
What You Should Pay Attention To
If your testicle moves up during cold weather, sex, or exercise and comes back down afterward, there’s almost certainly nothing wrong. This is a reflex your body is supposed to have.
The situations that warrant a closer look are different. If one or both testicles spend most of their time outside the scrotum and don’t come back down on their own, that’s worth getting evaluated. The same applies if you notice the testicle sitting higher than it used to over a period of months, if there’s pain when the testicle moves, or if one testicle feels noticeably smaller than the other. These patterns can indicate an ascending testicle, which may eventually need to be surgically fixed in position to protect fertility and reduce long-term health risks.
For most people who search this question, the answer is reassuringly simple: you have a muscle doing exactly what it evolved to do. The testicle goes up, the testicle comes back down, and your body moves on.