If you're looking to improve your health and fertility, you may assume that adding in exercise is one of the best actions to take. And while that is partially true, it's not the entire story. Even with exercise, too much of a good thing can be bad.
Some studies have shown that "too much" exercise may impede fertility. This doesn't only apply to women who exercise to the point of lowering their weight levels below the healthy range, but even to women who maintain a normal weight and continue to get regular menstrual cycles.
On the other hand, obesity can also lead to lower fertility. To combat obesity, a combination of diet and exercise is needed. Regular exercise can also lower stress, which is important when you're trying to cope with infertility.
So, how much exercise is too much? And how might too much exercise lead to infertility? To get more details on the connection between exercise and fertility, read this excerpt from UpToDate -- a trusted electronic reference used by many physicians and patients.
Then, read on for what all of this means for you.
"In some epidemiological studies, more than seven hours per week of aerobic exercise has been associated with ovulatory infertility. In women undergoing in vitro fertilization, four or more hours of strenuous exercise weekly over a period of years has been associated with poorer outcomes.
The effects of strenuous exercise on fertility could be related to (1) reduced progesterone production during the luteal phase of the menstrual cycle in ovulatory women (ie, luteal phase defect), (2) alterations in GnRH production, LH and FSH secretion, and estradiol production and metabolism, resulting in anovulation, or (3) changes in leptin levels. Other factors may include decreased body fat and changes in diet, such as an increase in fiber and a decrease in fat intake, in women who exercise strenuously.
From a population perspective, inadequate levels of exercise associated with obesity may be a more common cause of anovulation and subsequent infertility than exercise associated anovulation."
Infertility and Too Much Exercise
Too much exercise seems to impair ovulation, and there are a few theories on why this happens.
One possible result of too much exercise is a luteal phase defect. The luteal phase is the time period between ovulation and your expected period. This time period, also known as the "two week wait", is normally between 12 and 16 days. A shorter luteal phase can interfere with getting pregnant.
Normally, progesterone levels remain high during this time, to allow a fertilized egg to attach itself to the uterine lining. Low levels of progesterone can interfere with a fertilized egg implanting, which leads to infertility.
Another potential reason for exercise-induced infertility is that the hormones responsible for regulating the female reproductive system -- GnRH, LH, FSH, and estradiol -- are changed in ways that interfere with ovulation.
Yet another potential cause for exercise-induced infertility is changes in leptin levels, which regulates appetite and metabolism. If your appetite is low, you may not eat enough, which can interfere with regular ovulation.
It's also possible that women who exercise more than 7 hours per week are more likely to restrict their diet. Not eating enough healthy fats, losing weight rapidly, or weighing below the recommended weight guidelines for your height can affect ovulation.
What If I'm Overweight?
While too much exercise is a problem for some women, there are more women with the opposite problem - not enough exercise, leading possibility to obesity. Research shows that being overweight can also impair fertility.
The good news is that losing just a 10% of your current body weight has been shown to help fertility in women who are overweight. If your BMI is over 27, and you're trying to lose weight, you shouldn't shy away from exercise.
I'm Not Overweight, But I Like to Exercise. What Should I Do?
Exercise has many health benefits, and taking control of one's body can be empowering when trying to cope with infertility. With that being said, if you're trying to conceive, and your regular routine involves more than seven hours of intense exercise a week, you may want to cut back.
You may also want to consider replacing some of your more intense workouts with gentler forms of exercise. For example, instead of taking a high power aerobics class every day, you can replace some of your workouts with gentle yoga or leisurely walking. You'll still get to enjoy moving your body, but you won't be overtaxing your system.
Want to learn more? See UpToDate's topic, "Optimizing natural fertility in couples planning pregnancy", for additional in-depth, current and unbiased medical information on infertility, including expert physician recommendations.
Olek, Michael J., Gibbons, William E. "Optimizing natural fertility in couples planning pregnancy." UpToDate. Accessed: September 2009.