Sperm production runs best when the testicles stay roughly 2 to 4 degrees Celsius cooler than the rest of the body. That temperature gap is why the scrotum sits outside the abdomen. It also explains why most exercise advice about male fertility is not about banning squats or deadlifts. It is about managing heat, pressure, and duration. No common exercise is categorically off-limits, but certain training patterns keep the scrotum hotter and more compressed than it needs to be.
The research is clearest for anything that combines prolonged sitting with trapped heat. Sauna-level heat temporarily lowers sperm count and can worsen morphology, and the effect reverses once heat exposure stops (Garolla et al., Human Reproduction, 2013). Exercise does not usually reach sauna-level heat, but the same principle applies at lower intensity over longer periods. Before changing your training, it helps to know exactly which variable is doing the work.
Why heat matters more than the exercise itself
Sperm production happens in cells that are sensitive to temperature. The process works best a few degrees below core body temperature, and sustained heat pushes it in the wrong direction. A 2015 review in Reproductive BioMedicine Online described sperm production as dependent on that cooler environment (Durairajanayagam et al., 2015).
The everyday evidence points the same way. Tighter underwear and sitting raise scrotal temperature compared with looser underwear and movement (Jung et al., Human Reproduction, 2005). Sitting itself was enough to raise scrotal temperature in controlled measurements (Jung et al., 2005), and a separate study found that scrotal temperature stayed higher in men who sat for long periods compared with those who moved (Mieusset et al., Journal of Andrology, 2007). A laptop held on the thighs does the same thing by adding an external heat source (Sheynkin et al., Human Reproduction, 2005). The pattern is consistent. Any position or clothing that presses the testicles against the body and blocks airflow raises scrotal temperature.
Men who reported wearing looser, boxer-style underwear had higher sperm concentration and total count in a fertility-center cohort (Minguez-Alarcon et al., Human Reproduction, 2018). That is an association from an observational study, not a randomized trial, but it points in the same direction as the temperature physiology.
Exercise becomes a fertility variable when it mimics that pattern. Seated, compressive, and long duration are the three features that appear again and again.
Cycling and other seated endurance work
Cycling gets the most attention because it combines two variables at once. The saddle presses into the perineum, which can compress nerves and reduce blood flow through the area. The seated posture also keeps the testicles close to the body and limits air movement. Add the mechanical pressure of a saddle and you have a plausible reason to pay attention.
The long-term fertility evidence is mixed. Some observational research in cyclists has reported differences in sperm parameters, while other studies have not found a clear signal. The short-term symptoms are better documented. Numbness, perineal discomfort, and temporary erectile changes can happen after long rides, and they usually resolve when the rider gets out of the saddle. For fertility specifically, the concern is less about one ride and more about many hours per week spent in that seated, compressed position.
Adjustments that some riders use include:
- A saddle with a pressure-relief cutout
- Padded shorts
- Standing up every 15 to 20 minutes
- Looser, breathable underwear during rides
The goal is to break up the pressure and let some air move through the area.
Heavy lifting and the Valsalva myth
Heavy squats, deadlifts, and leg presses spike intra-abdominal pressure. That is real. What is not established is that this pressure spike damages sperm production. The existing evidence does not link heavy resistance training to lower sperm quality in healthy men.
The confusion usually comes from varicocele. A varicocele is an enlarged vein in the scrotum, and it is a known contributor to male infertility. Some men wonder if heavy lifting causes it. The evidence does not support that. Varicocele is a vein structure issue, not a direct result of a few heavy sets. If a man already has a varicocele, the conversation about training should happen with his doctor, because the condition itself can raise scrotal temperature and affect sperm parameters.
One edge case worth naming is extreme leanness. Some men who maintain very low body fat for long periods through chronic energy restriction experience changes in reproductive hormones. That is a nutrition and recovery issue more than an exercise choice. The lifts themselves are not the main variable in that scenario.
Clothing and environment during exercise
The exercise itself is rarely the whole problem. The clothing and environment often matter more. Training in a sauna suit, wearing thick compression shorts for long sessions, or doing hot yoga in non-breathable fabric can keep scrotal temperature elevated well beyond the workout. Sitting in sweaty gear after a ride extends that exposure.
One useful finding from the research is that the system is resilient. Heat-related sperm changes reversed after heat exposure stopped in the Garolla et al. (2013) study. Shefi et al. (2007) found that men who stopped wet heat exposure saw semen parameters recover. That does not mean chronic heat is harmless. It means a single hot workout is not a fertility emergency. The risk lives in patterns, not isolated events.
What deserves your attention
A practical way to think about this is to look at your training week and ask which sessions keep the scrotum hot, compressed, and pressed against the body for long stretches. For many men, the list is short.
Prolonged cycling with a standard saddle is the classic example. Hot studio sessions in tight, non-breathable clothes are another. Long rows or seated endurance work can matter if the seat traps heat. None of these need to be eliminated. The fix is usually in the setup and the habits around the session.
Some men find that simple changes make a real difference: a different saddle, looser shorts, standing up more often, and getting out of sweaty gear when the session ends. Others reduce the frequency of the hottest environments or add a cool-down period before sitting for a long stretch. The common thread is giving the testicles a chance to return to their preferred temperature.
If you are actively trying to conceive or have had a semen analysis come back abnormal, that changes the stakes. A doctor who specializes in male fertility can review your training habits alongside the rest of your health picture and help you decide what to adjust. This post is not a substitute for that conversation.
This content is for educational purposes only and is not medical advice. Oakman products are designed for physical comfort and cooling. They make no claims about fertility, sperm quality, or hormone levels. Consult a healthcare professional for personalized advice.