If you hope to start a family soon, you've already heard you need to eat a nutritious diet, cut back on booze, and keep your weight in check if you want to keep your sperm healthy. Now researchers have identified another key enhancer of sperm quality: moderate-intensity exercise.
Experts have long theorized that working out aids fertility, but most previous studies have relied on self-reported exercise data, which is notoriously unreliable. This new trial, published in the journal Reproduction, provides the most solid evidence yet that exercise is good for your swimmers, and pinpoints which type of workout is best.
German researchers divided 280 sedentary men with no known fertility issues into four groups and then tracked their sperm health over 24 weeks. The first group kept on doing no exercise, while the second group completed 30- to 45-minute moderate-intensity treadmill runs three times a week. The third group did three weekly 40- to 60-minute treadmill runs at a continuous high intensity, and the remaining men knocked out three 10- to 15-minute sessions of high-intensity interval training, or HIIT, a week.
By the study’s end, all three exercise groups had healthier sperm than the non-exercisers. They showed improvements in motility, shape, and concentration and had less oxidative damage to the DNA of sperm cells.
"All of these changes are associated with less inflammation," says Dr. Peter Schlegel, vice president of the American Society of Reproductive Medicine and chief urologist at Weill Cornell Medicine in New York City. "Exercise could have caused lower inflammation with subsequent improvements in sperm quality." Or, since these men all dropped pounds over the course of six months, which alone can curb inflammation, Schlegel says their healthier sperm may have stemmed indirectly from weight loss.
But of all the men who worked out, the healthiest sperm belonged to the moderate-intensity group. They had better parameters all around than both the HIIT group and those who did long runs at a continuous high-intensity pace. There are a few possible explanations for this. "Intense exercise can create higher body heat, and the testes need to remain at lower-than-body-temperature heat for optimal function," Schlegel says. "Also, moderate exercise was associated with greater weight loss and improved body fat compared to more intensive or episodic exercise."
These findings make it clear that if you’re thinking babies and have fallen off the workout wagon, it’s time to drag your ass back to the gym. But what if you’re already doing long bouts of high-intensity exercise nearly every day? Should you adjust your program to support your sperm? Schlegel thinks yes.
"Over 1.5 hours of vigorous cardiovascular activity per day can decrease sperm production," he says. "So if you already work out and now want to optimize your fertility potential, it’s worth trying to limit exercise to a maximum of one hour a day."
If that’s too little for you, shift part of your workouts to the pool. Schlegel says increased body heat is usually less of an issue when swimming. Another option is to dial back a bit on cardio but ramp up strength training, which will yield big-time body benefits beyond just your sperm.
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