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Physical labor is linked to semen health, new research finds

Over the last four decades, sperm count has declined by about 50–60%, with researchers citing poor diet, obesity, stress, insufficient sleep, and exposure to endocrine-disrupting chemicals as potential causes. Now a new study has found that sperm health may be related to the kind of work you do, with physically demanding jobs related to higher sperm concentration and higher testosterone levels.

Read on to find out what this study says about physical labor and sperm health, what researchers have uncovered about exercise and male fertility, and what you can do to protect your fertility if you have a sedentary job.   

Key takeaways

  • A recent study found that men who reported frequently lifting or moving heavy objects at work had 46% higher sperm concentrations compared to men with jobs that don’t involve heavy lifting.
  • The study also found that men with heavy or moderate levels of physical exertion at work had higher circulating testosterone concentrations compared to those with lighter exertion.
  • For people with less physically demanding jobs, adopting a regular exercise routine including weight lifting may help you reap the benefits cited in this research.

Physically demanding occupations tied to improved semen health

In a study published in April 2023 in the journal Human Reproduction, researchers uncovered a link between physically demanding occupations and higher testicular function.

The study, co-authored by Legacy’s chief medical officer Ramy Abou Ghayda and funded in part by Legacy, analyzed the occupations of 377 male partners of couples seeking infertility treatment at a fertility center between 2005 and 2019.

The researchers found that men who reported frequently lifting or moving heavy objects at work had 46% higher sperm concentrations and 44% higher total sperm count compared with men who reported never lifting or moving heavy objects at work. There were similar results for men involved in heavy levels of physical exertion compared to those with light levels at work.

Sperm concentrationTotal sperm count
Men who never move/lift heavy objects at work32.2 million sperm/mL82.7 million
Men who sometimes move/lift heavy objects at work40.4 million sperm/mL100.0 million
Men who often move/lift heavy objects at work59.6 million sperm/mL149.0 million

The study also found that men with heavy or moderate levels of physical exertion at work had higher circulating testosterone concentrations — a mean of 515ng/dl — compared to those with lighter exertion, who had mean T levels of 427 ng/dl. That’s an increase of approximately 20% associated with more physically demanding work.

Men who often moved or lifted heavy objects at work also had higher estradiol concentrations, compared to those who never did. Though estradiol is a form of estrogen, research indicates it is essential for modulating libido, erectile function, and spermatogenesis.

The findings come at a time when male fertility rates seem to be steadily declining, with sedentary lifestyles being one potential contributor.

Does physical labor cause better fertility?

Maybe. This study finds a correlation, but doesn’t necessarily indicate that physical labor is the cause of better fertility or higher testosterone levels. It’s also possible that men who have naturally higher testosterone levels are overrepresented among those who do physical work.

However, we have a good evidence base to suggest that physical activity and exercise in general are associated with improved sperm health.

How exercise affects male fertility

While the study cited above is new, the idea that physical activity improves male fertility is well documented.

According to a 2019 study, regular exercise is associated with increased sperm motility, which refers to the ability of the sperm to move swiftly and efficiently toward their destination — the egg. Along with sperm motility, there is evidence that exercise can also increase sperm count and testosterone levels, both important factors in male fertility.

Regular exercise is also key to maintaining a healthy weight, which is also crucial for healthy sperm and hormonal function. Excess body weight is associated with hormone imbalances, erectile dysfunction, systemic inflammation, poor sperm motility, and low semen quality.

Exercise and sperm count 

Does exercise increase sperm count? Research has shown that men who engage in moderate exercise for one hour at least three times per week may see increases in their sperm count as well as motility. 

There may be even more benefits for those who like to lift heavy. As the study in Human Reproduction showed, moving heavy objects as part of a job was associated with higher sperm concentrations.

Does intentional weight training affect male fertility in a similar way? Experts say yes. One study shows that weightlifting and outdoor activities are associated with higher sperm concentration. In fact, men in the highest quartile of weightlifting — those who lifted weights more than 2 hours per week — had 25% higher sperm concentrations than men who never lifted weights.

Exercise and testosterone

Though only small amounts of testosterone are required for sperm production and maturation, the hormone plays an essential role in male fertility. Low testosterone has been linked to a number of factors like low libido and erectile dysfunction, which can make it difficult to conceive. Exercise is one way to increase testosterone naturally.

In a 2012 study, researchers found that physical activity was linked to higher levels of testosterone, FSH, and LH — all the hormones that control sperm production — compared to men who were sedentary. The study also found that exercise resulted in “statistically significant differences” in numerous semen parameters, such as total progressive motility and morphology, which refers to shape, size, and structure of sperm.

But not all exercise is equal. Interestingly, a study from the University of Texas found that performing squats synthesized more testosterone and growth hormone than a similar session on the leg press.

There may even be evidence that exercise is more beneficial for increasing testosterone than losing weight, as suggested by a 2016 study of obese men. This study found that exercise increased testosterone levels significantly more than weight loss induced by calorie restriction (eating less).

I have a sedentary job. What can I do to improve my fertility?

If you have a desk job that doesn’t involve heavy lifting, there are still a number of things you can do to improve your sperm health, testosterone levels, and overall health.

The number one thing is to adopt a regular exercise routine. Join a local gym, start lifting weights in your garage, or simply jog around the block. The research is clear that physical activity can benefit your fertility, as well as whole-body health.

Other changes to improve your fertility include:

  • Eat more vegetables and fruits
  • Cut down on fried foods, refined grains, added sugars, processed foods, and red meat
  • Take male fertility supplements to fill gaps in your diet
  • Stop smoking
  • Limit alcohol consumption to fewer than five drinks per week
  • Lower your stress levels
  • Get adequate sleep
  • Avoid endocrine disruptors like those found in plastics and hygiene products

Not sure if you need to improve your fertility? Take Legacy’s at-home sperm analysis to assess the five key metrics of your sperm health and receive personalized recommendations on what you can do to increase your chances of having a child, whether you’re trying now or hope to do so in the future.

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