My patients always want to know what they can do to boost their fertility and the chance at getting pregnant with fertility treatment. I usually advise them to improve their diet and get more regular exercise as part of our plan. However, too much exercise can be just as harmful to fertility as not enough.

The problem is significant for men and women alike — and, in many cases, hard to detect until the couple tries to conceive. Here’s a breakdown for each of the sexes and how intense exercise interferes with their plans to get pregnant.

Women who regularly participate in strenuous workouts (e.g., triathlons, marathons) are more likely to have menstrual irregularities. When you can neither predict when the egg will be present nor whether it will be viable for fertilization, you decrease your chances of getting pregnant that month.

There is a delicate balance of factors working together in a woman’s body every month. She needs a certain amount of body fat (at least 17 percent, although 18 to 22 percent body fat is even better) to maintain the proper ratios of hormones that stimulate the follicle development and the related endometrium lining. Too little fat, and there isn’t enough estrogen available to keep everything in balance. In other cases, there might not be enough ovarian hormones present to prepare a nutrient-rich and thick endometrium lining to receive a fertilized embryo.

In many cases, however, female athletes don’t realize there is an issue because their periods continue as usual, so they assume everything is functioning normally. It is only after they try to become pregnant, have problems and do a fertility workup with a fertility specialist that they realize there is an issue.

Men who participate in intense workouts with little rest in between have lower sperm counts than men who only exercise moderately and more issues with sperm formation (morphology) and movement (motility). These are the three factors measured to determine male infertility. Sperm needs to be healthy and able to swim to get to the egg — and the more there are, the better.

When it comes to sperm formation, it is important that men give their bodies time to rest and repair so their sperm is at its best for fertilization. When the workouts are too intense and too frequent, their bodies suffer oxidative stress, resulting in cellular damage.

Like women, men are usually unaware there is an issue until they have a problem conceiving with their partners. A simple analysis of a sample can determine if male infertility is a factor.

So how much is too much? Strenuous exercise could include:

  • Back-to-back workouts, particularly for marathon or triathlon training
  • Weight/strength training should have at least two days of rest between sessions
  • Cardiovascular exercise that exceeds 65 to 75 percent of a person’s maximum ability

When it comes to exercise, regularity is key. Most experts agree that men and women alike should strive to get at least one hour of exercise three times a week, in the 65 to 75 percent of capacity range. This exercise should be moderate in intensity and include both strength and cardiovascular training. It’s also a good idea to engage in relaxation exercises every day as well, to help facilitate muscle repair. Men should also try to avoid overheating the testes, as that can lead to lower sperm counts as well.

Regular exercise is an important part of your fertility-boosting plan. Exercise has been proven to help infertility patients lose excess weight that can affect their ability to experience regular ovulation. Also, it can serve as stress relief for patients undergoing fertility treatment. But there are times when the gym makes infertility worse. And that’s when too much of a good thing becomes a bad thing for your family-building dreams.