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Testicle Temperature: How Heat Impacts Fertility

Is heat killing your sperm? In humans, sperm production is temperature dependent with normal testicular function requiring a temperature of 2–4°C below the general body temperature. The testicles’ ability to hang lower when too warm and retreat when too cold regulates the scrotal temperature. The tissue surrounding the testicles (blood network, fat, skin) also regulates the temperature in the scrotal sack.

Numerous external factors – such as posture, clothing, lifestyle, fever and season of the year – can affect the temperature of the scrotum and may have an impact on sperm quality if prolonged.

Heat is killing your sperm

Several experimental studies show that an artificial increase in scrotum or testicle temperature can reduce both sperm count and quality [1]. This has increased the focus of researchers to understand the adverse effects of factors that may increase the scrotal temperature.

Some studies show that males in certain occupations (bakers, mechanics, drivers) have a higher risk of decreased sperm quality. This is most likely because of increased testicular temperature. Along the same lines, a study from 2014 with 336 males revealed an association between self-reported occupational heat exposure and sperm DNA quality. The main finding was that males who were exposed to high temperatures and sat for more than six hours during work showed an increased sperm DNA damage [2].

What does heat do to sperm concentration and motility?

In a 2015 study researchers investigated how high testicular temperatures of 40-43°C affect semen parameters. The experiment included 40 minutes of heating for two days during a 3-month period for 19 healthy men. Researchers found that increased temperature reduced sperm concentration (From 73M/ml to 42M/ml) and sperm motility (71% to 25%) to about half of the initial values [3]. Importantly, removing the heat stimulation improved the sperm parameters.

In a similar study, five men wore specially designed underwear forcing the testicles to be pushed up for 15 hours a day for 120 days. The estimated increase on scrotal temperature for each participant was about 2°C. Sperm parameters (motility and total sperm count) decreased after three weeks and remained low until the end of the experiment. These parameters returned to normal levels 73 days after the end of the experiment (see figure below) [4].

Figure 1

Figure 1 shows a decline in sperm count during heat exposure in a group of men who wore a type of underwear that forced the testicles to be pushed up so they were not able to hang freely. Sperm count increased again after the participants stopped wearing the underwear on day 120 [4].

This finding is similar to a study which showed that men who wore tight underwear had a lower semen quality compared to those who wore loose underwear [5].

Keep your testicles cool

Going through the scientific literature on heat and sperm we can conclude that heat exposure is a significant risk factor for male infertility. Induced heat to the testicles can affect sperm count, motility, and even genetic material. Especially occupational work where men are repeatedly subjected to abnormal situations may, in time, lower sperm motility and concentration. A lifestyle with tight underwear, exposure to heat from hot baths or cell phones, may also pose a risk factor for male infertility. The good thing is that it seems the negative effects are reversible!

Don’t let the heat kill your sperm! To allow for proper temperature control of the scrotal area, you should avoid:

  • tight underwear and pants – swap these for looser ones.
  • sitting down for several hours at a time. Get up and get some air to the region – let your balls hang.
  • having laptops or other hot objects near the genital area for a prolonged time.
  • long spinning classes or too long bike rides.
  • long warm baths, hot tubs, and saunas.
  • storing your mobile phone in your front pants pocket near your genital area


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Wearing tight pants and underwear

Studies show that men who wear looser underwear have higher sperm concentration and total sperm count compared to men who wear tighter underwear. So, lose the tight clothes and wear something loose to give your testicles some air.

CONCLUSION: learn more about how heat can affect sperm quality here.


Besides higher mortality rate and various diseases, stress is associated with low sperm quality. Stress is known to be associated with lower testosterone levels and oxidative stress with both playing an essential role in producing and maintaining healthy sperm cells.

CONCLUSION: If you feel stressed, we recommend you get some help so you can have a balanced mental health. For a stress management guide, download the ExSeed app for free and start your personalized action plan today.

Physical activity

Scientific studies show that men who are physically active have better semen parameters than men who are inactive. Fertility specialists also state that regular physical activity has beneficial impact on sperm fertility parameters and such a lifestyle can enhance the fertility status of men.

Prioritizing exercise can help improve your overall health and result in healthy, fast swimming sperm cells that have good chances of fertilizing an egg.

CONCLUSION: Try incorporating exercise in your weekly schedule to you ensure exercising at least twice weekly. We recommend a combination of cardio training and strength exercise. Read more about exercise and male fertility on our blog.


Fast Food
Processed foods damage the health of sperm-producing cells and cause oxidative stress, which lead to poorer sperm quality. Heavy consumption of junk food (every week) can increase the likelihood of infertility since men who consume vast amounts of unhealthy food are at risk of having poor sperm quality. Besides harming your fertility, junk food enlarges your waistline, harms your cardiovascular system, kidneys, and more.

Eating more fruit and vegetables can increase your sperm concentration and motility. It’s important that you consume a healthy diet filled with antioxidants and that you eat vegetables every day. Foods such as apricots and red bell peppers are high in vitamin A, which improves male fertility by nurturing healthier sperm. Men who are deficient in this vitamin tend to have slow and sluggish sperm.

Sugary snacks/beverages: several times a week Excessive consumption of high sugar items can lead to oxidative stress, which negatively impacts testosterone levels and sperm motility. Sugary snacks and beverages are also highly associated with obesity and low fertility.
CONCLUSION: To boost sperm quality, stay away from fast food, processed food, and sugary snacks or beverages. You need to implement a healthy prudent diet filled with necessary superfoods needed for good sperm production. Check out our guide to Male Fertility Superfoods. For personalized guidance and support on how you can start improving your sperm health, check out the Bootcamp.


Direct heat can inhibit optimal sperm production and cause Sperm DNA damage. Sperm cells like environments that are a couple of degrees lower than body temperature. Avoid overheating from warm blankets, seat warmers, heat from your laptop, hot showers, and saunas.

Cigarette smoking

The exposure to tobacco smoke has significant negative effects on semen quality. The damage of cigarettes and nicotine of course depends on how many cigarettes you smoke per day and for how long, but even low usage (up to 10 cigarettes / day) can inhibit healthy sperm production.  

CONCLUSION: Stay as far away from cigarette smoking as possible if you care about your general health and your fertility. Read more here.

Cell phone

When you have your cell phone in your front pocket, your testicles are exposed to electromagnetic radiation, which studies have shown to damage the sperm cells. Put your phone in the back pocket of your pants or in your jacket pocket.


There is a clear association between obesity and reduced sperm quality. At least part of the reason for this is that obese men may have abnormal reproductive hormonal profiles, which can impair sperm production and lead to infertility. 

A BMI higher than 30 can lead to several processes in the body (overheating, increase in oxidative stress in the testes, sperm DNA damage, erectile dysfunction) that can have a negative impact on male fertility. This can result in problems when trying to conceive.  

CONCLUSION: BMI is one of the risk factors that influence semen quality and, for example, sperm motility.  


A beer or glass of wine now and then do not really harm sperm quality. But excess alcohol drinking (more than 20 units per week) can reduce the production of normally formed sperm needed for a successful pregnancy.

CONCLUSION: If you want to stay safe, stay under 14 units of alcohol per week. For more information on how alcohol can affect male fertility, take a look at our blog: “Alcohol and Sperm Quality”.


Studies show that women younger than 35 and men younger than 40 have a better chance of getting pregnant. Men can produce sperm cells almost through their entire life, but the sperm cell DNA is more fragile and prone to damage after the age of 40.

As men age, their testes tend to get smaller and softer resulting in a decline in sperm quality and production. These changes are partly because of an age-related decrease in testosterone level, which plays a very important role in sperm

production. Higher male age (>40 years) is not only associated with a decline in sperm production but also with increased sperm DNA fragmentation and worsened morphology (shape) and motility (movement). These negative effects make the sperm cells less qualified for egg fertilization.

CONCLUSION: with an age under 40, you shouldn’t have to worry much about age as a factor in itself. However, studies have shown a slow decline after the age of 30-35 years

and if you are above 40 years of age, your sperm quality can be affected due to increased sperm DNA damage resulting in a decrease of sperm motility and concentration. Remember that you cannot evaluate the quality of a sperm sample by just looking at it – this requires a sperm analysis.