In 2005, researchers at SUNY Stony Brook had men work with a laptop balanced on their knees for an hour. Scrotal temperature rose by about 2.6°C (Sheynkin et al., Human Reproduction, 2005). That single finding points at the real question behind exercise and fertility: which activities keep the testicles hot or compressed long enough to matter?
Most exercise works in your favor. Regular moderate activity supports the body weight, sleep, and insulin sensitivity that reproductive health depends on. The exercises worth a second look are the ones that create sustained heat, sustained pressure, or both. For most men, that narrows to a few specific situations.
Why temperature controls the conversation
The testicles sit outside the body because sperm production needs a temperature a few degrees below core body temperature. When heat exposure becomes regular or prolonged, sperm count drops and sperm shape can worsen. A 2013 study in Human Reproduction found that sauna-level heat temporarily lowered sperm count and worsened morphology, and the effect reversed once the heat exposure stopped (Garolla et al., Human Reproduction, 2013).
Exercise rarely heats the testicles as aggressively as a sauna. Some forms of training do reproduce a milder version of the same conditions. The difference is duration. A short run or a heavy set of squats raises core temperature briefly. The body sheds that heat quickly. A 90-minute spin class in a warm room does not.
The exercises worth a second look
Long-distance cycling and indoor spin classes
Cycling deserves the most attention because it combines three heat-unfriendly factors at once: a seated position, a warm saddle pressed against the perineum, and tight synthetic shorts that hold heat and sweat. Research on scrotal temperature shows that sitting itself raises temperature relative to standing and moving, and tighter underwear raises it further (Jung et al., Human Reproduction, 2005). The laptop study from 2005 makes the same point from a different angle. A working laptop raised scrotal temperature by about 2.6°C in 60 minutes. A bike saddle used for two hours does the same two things: it blocks airflow and holds body heat against the skin.
The effect is temporary and dose-dependent. If you ride a few hours a week, the heat load is modest. If you are logging 8 or more hours on a bike each week, or taking hot spin classes daily, and your semen analysis comes back below where you want it, cycling is one variable worth adjusting.
Hot yoga and heated training rooms
Training in a room heated to 32°C or higher raises skin temperature and can keep scrotal temperature elevated for the duration of the class. The mechanism is the same one researchers documented with sauna use: sustained heat exposure temporarily reduces sperm production (Garolla et al., Human Reproduction, 2013). One hot yoga class is unlikely to show up in a semen analysis. A daily hot yoga habit while trying to conceive is a different situation.
If you like hot yoga and you are trying for a child, one option is to take the same class in a non-heated room. You keep the mobility work and the breathing without the added heat load. Some men make that change only during the months they are actively trying to conceive.
Extreme endurance training
High training volume combined with low energy availability can push reproductive hormones lower. This pattern shows up in overtrained endurance athletes more often than in recreational runners or lifters. The contributing factors are too many hours, too little food, and too little recovery. When training load drops and energy intake returns, the numbers tend to follow.
The practical question is whether training has crossed into a chronic deficit. A 30-minute run most days does not create this problem. A 15-hour training week backed by poor sleep and skipped meals can.
Strength training does not belong on the avoid list
Heavy compound lifts raise heart rate and core temperature for a few minutes. That brief spike does not match the sustained heat exposure linked to sperm changes. The mechanical pressure of a squat or deadlift does not compress the scrotum the way a bike saddle does for an hour. If you are lifting in a cool gym with normal rest periods, you are not creating a fertility problem.
What the research says about exercise in general
Regular physical activity consistently shows up as a neutral-to-positive factor in male fertility research. The benefits come from body composition, cardiovascular fitness, and sleep quality, all of which matter for reproductive health. The men who run into trouble are usually at the extremes: either sedentary, or training at such high volume that recovery disappears.
That is why the question of which exercises to avoid is smaller than it sounds. You are looking for activities that add heat or pressure on top of an otherwise normal training routine.
Practical adjustments for men who are trying to conceive
No single workout will make or break fertility. The adjustments below reduce total heat and pressure exposure over time.
- Stand out of the saddle every 15 to 20 minutes on long rides.
- Choose a bike saddle with a cutout if you ride more than a few hours a week.
- Swap hot yoga for a room-temperature class during the months you are trying.
- Change out of sweaty compression shorts right after training.
- Wear breathable, non-constrictive underwear during the rest of the day.
- Keep laptops off your lap, and avoid long stretches of sitting in a car with heated seats on high.
The underwear point has direct research behind it. In a 2018 study of men at a fertility center, those who reported wearing looser boxer-style underwear had higher sperm concentration and total count than men who wore tighter styles (Minguez-Alarcon et al., Human Reproduction, 2018). The exercise version of that finding is straightforward: whatever you wear during and after training affects scrotal temperature more than a single workout does.
The underlying principle is simple. The scrotum is not built to stay warm for hours at a time. Small changes in position and airflow let it return to the cooler temperature it needs.
The heat effect is reversible
The most useful piece of research on this topic is also the most reassuring. A 2007 study followed men who stopped regular wet heat exposure after abnormal semen results. Semen parameters recovered, with improvements appearing over several months (Shefi et al., Fertility and Sterility, 2007). Sperm production runs on a cycle of roughly 74 days, so a change you make today often shows up in a semen analysis two or three months later.
If you are concerned about a specific exercise habit and your numbers, the evidence-based approach is to reduce the heat or pressure for one full sperm cycle and retest. That gives you a clear answer without guessing.
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.