Can Physical Labor Improve Men’s Fertility?

Carpenter toold
Stay active, stay creative, stay fertile! (Courtesy Unplash)

Not sure why, but I’m a big fan of manual labor. Maybe it’s because my dad was a blacksmith and welder who could build or fix anything. A true master of manual intelligence, his self-worth was tied to the fact that the building stands, the gadget works and the lights are on, and not on “chattering interpretations of himself.” Pretty sure that’s why I became a surgeon, a real hands-on craft within medicine.

But the benefits of a life of manual labor go beyond the practical and the satisfying. It improves sleep: Farmers get the most sleep among all professions in the US. And, by burning more calories, manual labor reduces obesity and the risk of diabetes. Did you know that you burn 50 calories/hour just by standing and not sitting? Working with your hands improves coordination and muscle tone and promotes new dimensions of learning and memory that differ from “book knowledge.” Finally, making or doing things by hand builds character by offering a unique perspective on work, how money is earned (“sweat equity”), and job satisfaction. But I have often wondered whether manual labor is good for fertility.

Raising Rocks Rocks

My suspicion is manual labor is good for us as species, as our hunter-gathering forebears were largely manual laborers and not at desks. A recent study from Harvard also suggests that, yes, engaging in manual labor may be a plus for a man’s fertility. Among infertile men, they found that those who reported often lifting or moving heavy objects at work had 46% higher sperm counts compared to those with less physical jobs. They also had significantly higher testosterone levels than the less-active control group. One limitation here is that all men evaluated were infertile. The question is whether this is true for the average Joe who is not necessarily infertile. Since this hasn’t been studied much, we’ll need to pivot to research that simply looks at fertility potential associated with exercise instead.

Let’s Get Physical:

Among the dozen or so studies that have examined exercise levels among men who are not infertile, the vote is that those who exercise regularly have better semen quality than those who don’t. Among 189 University of Rochester students between the ages of 18 to 22, those who watched more than 20 hours of TV weekly had a 44% lower sperm counts than those who watched almost no TV. Men who exercised for 15 or more hours weekly at a moderate to vigorous rate had a 73% higher sperm count than those who exercised < 5 hours per week. Similar findings were observed in study of 261 healthy 25–40-year-olds at Urmia University in Iran. But there also appears to be a limit as to how much exercise is good for fertility. Sperm counts and motilities appear to be the highest in studies of recreational athletes and actually lower among elite or professional athletes who undertake extreme exercise. A meta-analysis of 10 studies that looked at this issue concurred that there was a 14% decrease in fertility among high-intensity physical activity compared to low or moderate levels. This suggests that extreme physical stress, like that associated with the stress of constantly running from woolly mammoths in neolithic times, is not good for fertility.

So, like exercise, heavy manual work is a healthy thing in many ways, including fertility. And despite the increased use of ChatGPT and other AI applications, which have the potential to threaten the livelihood of many professionals with automation, AI is unlikely to replace jobs that involve creativity, problem-solving, and emotional intelligence. So, keep moving and stay creative!