A 2012 study in the European Journal of Applied Physiology compared physically active men with sedentary men and found the active group had higher sperm concentration, motility, and morphology, along with higher testosterone levels (Vaamonde et al., 2012). That sounds like a clean endorsement of exercise. The full picture bends around dose, heat, and what happens to the groin during and after training. Too little movement can be a problem. Too much, done the wrong way, can be another.
Moderate Movement as the Baseline
The most consistent finding in this area is that regular moderate activity beats being sedentary on most semen quality measures. The Vaamonde study is one example. Other observational work points the same direction, although the studies are not all prospective and many come from fertility clinic populations. A reasonable reading is that normal physical activity is associated with a hormonal and metabolic environment sperm production relies on, without making the testicles overheat.
Moderate means different things to different men. Brisk walking, swimming, recreational jogging, rowing with short breaks, and strength training a couple of days per week all fit. The standard general-health target of about 150 minutes of moderate activity per week is a sensible reference point. More activity is not automatically better for fertility.
The Heat Problem Is Mechanical
Sperm production needs the testicles to sit a few degrees below core body temperature. The scrotum manages this with its position, blood flow, and sweat. Heat stresses the temperature-sensitive cells that make sperm. Garolla et al. (Human Reproduction, 2013) showed that sauna-level heat temporarily lowered sperm count and worsened morphology. The effect reversed once the heat exposure stopped. A 2015 review in Reproductive BioMedicine Online summarized the mechanisms by which repeated testicular heat stress reduces sperm count and quality (Durairajanayagam et al., 2015). Those studies are sauna and heat, not exercise, but the same principle applies to training. Exercise that traps heat against the groin drives scrotal temperature up.
Tight clothing and sitting already raise scrotal temperature. Jung et al. (Human Reproduction, 2005) measured higher scrotal temperature in men wearing tight underwear compared with looser options. Mieusset et al. (Journal of Andrology, 2007) found that sitting raised scrotal temperature relative to standing and walking. Sheynkin et al. (Human Reproduction, 2005) measured an increase in scrotal temperature when men used a laptop on their thighs. None of those are exercise, but they describe the same mechanism: trapped heat.
From a fertility standpoint, the worst exercises are the ones that combine high body heat with long duration and tight, heat-holding clothing. Spin classes in a heated room, long stationary cycling sessions in padded shorts, hot yoga, and high-volume running in compression tights all fit that pattern. The movement pattern itself matters less than the temperature and pressure environment around the testicles.
Cycling Is the Most Studied Worst Case
Cycling deserves its own section because it is the exercise with the most direct observational research, and the findings are mixed. Wise et al. (Fertility and Sterility, 2011) studied men attending a fertility clinic and found that cycling five or more hours per week was associated with lower sperm concentration compared with no cycling. The study was cross-sectional, so it cannot prove cycling caused the lower numbers. The mechanism is plausible: tight padded shorts, a warm saddle, long seated duration, and limited airflow.
Recreational cycling is not the same as high-volume cycling. A 30-minute commute or a weekend ride below an hour does not create the same heat load as five hours a week in padded bib shorts. If cycling is your main training and you are trying to conceive, some men choose to alternate with swimming or running, wear looser clothing, stand on climbs, and change out of sweaty shorts immediately. These are practical adjustments, not prescriptions.
Resistance Training: Useful, Not a Fertility Drug
Heavy compound lifting causes a short-lived rise in testosterone after a session. That acute response is real, but chronic, large increases in testosterone from lifting alone are not well supported by controlled trials. The long-term picture depends on recovery, body composition, and training volume. Moderate resistance training two or three days per week is unlikely to harm semen quality, and it may help with body fat and insulin sensitivity, both of which matter to reproductive health.
The risk with resistance training is overdoing it. Overtraining syndrome, with insufficient recovery, raises cortisol and can suppress the hormones that tell the testicles to make testosterone and sperm. Relative energy deficiency in sport, which affects men as well as women, does the same. Usually the problem is the combination of huge training volume, a calorie deficit, and no rest days, not the deadlift by itself.
The Overtraining End
High-volume endurance training has its own caution. Some studies of marathon runners and ultra-endurance athletes have reported lower sperm concentration and motility, but the samples are small and the findings are not uniform. The likely contributors are heat, oxidative stress, elevated cortisol, and energy deficiency. High-volume endurance training also increases oxidative stress, which is one proposed mechanism for lower semen quality in overtrained athletes. One long run in loose shorts will not wreck your sperm count. Year-round high-volume training with little recovery might, especially if it keeps the groin warm for hours at a time.
Practical Adjustments
If you want to keep exercise as a positive for your reproductive health, the practical moves are straightforward.
- Wear loose, breathable shorts and underwear when you train.
- Avoid sitting in damp, hot gear after a workout.
- Alternate cycling with non-seated cardio like swimming, running, or rowing with breaks.
- Keep one or two full rest days per week.
If you have been trying to conceive for 12 months without success, or six months if your partner is over 35, a semen analysis is the clearest way to see where things stand. Exercise choices can be adjusted after that conversation, not before.
Put together, the available evidence points toward moderate aerobic work plus some resistance training, done in loose, breathable clothing, with enough recovery to avoid chronic heat and energy deficit.
When to See a Doctor
If you have concerns about fertility, the right person to talk to is a urologist or reproductive endocrinologist, not a personal trainer or a forum. A baseline semen analysis gives you concrete numbers instead of guesswork. If a doctor finds abnormal parameters, they can help you sort out whether exercise, heat exposure, lifestyle, or something else is contributing.
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.