• Rose Unwin

The best type of exercise for fertility

Updated: Sep 11, 2021

Looking to conceive and love to workout? This is a question that I was obsessed with because I'm a total fitness nut. I feel happy and full of vitality when I'm fit and strong. However, I'd never want to do anything to compromise my chances of conceiving or of growing a healthy baby in utero. Eek, how much exercise is too much?!

Whilst exercise is hugely beneficial to health, too much exercise places additional stress on the body and could impede fertility. Most clinicians say it's OK to continue the exercise your body is used to. I was training for Olympic & Half Iron Man distance triathlons - surely I shouldn't continue with the volume of high level training? Probably not, so I scaled it back to my 'base camp' fitness level. On a weekly basis includes a daily dog walk of 30-60 mins, a yoga session, a 5k and a 10km run and one full body strength session. Whilst this may sound like a lot of exercise still, I wouldn't push myself hard. This means I kept my heart rate in a lower zone - no more than 70% of max HR - and I lifted lighter weights than usual. In simple terms this is the difference between training for performance gains and doing exercise to maintain good health.


Doing at least half an hour of exercise three times a week may boost men's sperm count, say scientists. Moderately physically active men have significantly better sperm morphology (15.2%) in comparison with men who play competitive sport (9.7%), or who are elite athletes (4.7%). Other sperm health parameters showed the same pattern as above.

In one of the studies of 1,296 men, exercise increased the total number of sperms by 84.7%, which resulted in 191 out of 285 men getting pregnant in the exercise group but only 7 out of 263 in the control group who did no exercise. Men with a low semen quality asthenospermia (low motility) and oligospermia (low sperm count) were impacted the most. The exercise plan they followed was a combination of aerobic and resistance training, which included 30-35 minutes of walking/running on a treadmill and then 30-35 minutes of resistance training with exercises for all major muscle groups.

Are you a cyclist? A 10-year survey by a Boston-area (USA) fertility center observed 2,261 men—from all walks of life and not just elite athletes—who contributed over 4,500 samples of sperm. The study found that men bicycling more than five hours per week had a lower sperm concentration than either sedentary men or those doing other types of exercise. For more on the topic of cycling, check out my blog on this specific subject.


Regular moderate exercise has a protective effect on fertility. Moderate exercise is classified as one to five hours per week and this is found to improve fertility in women. However, excessive exercise can lead to menstrual abnormalities which could be to the detriment of your reproductive health. Five hours+ of cardio per week correlates with decreased fertility: cycle inconsistencies, implantation failure and live birth rate.

What is moderate exercise then? According to the American College of Sports Medicine (ACSM), moderate intensity aerobic exercise occurs when you reach 64%–76% of your age predicted maximal heart rate (which is calculated as 220 minus your age). You can wear a heart rate monitor or fitness tracker to help you determine if you are in a moderate heart rate zone.

I am 32 years old so my max HR is 220 - 32 = 188.

To find my aerobic HR zone I calculate 64% - 76% of my max HR.

188/100*64 = 120

188/100*76 = 143

If my HR is between 120 and 143 bpm (beats per minute) then I'm within my aerobic zone during exercise. I hope this example is helpful.

Too much vigorous exercise seems to impair ovulation in women of normal weight, and there are a few theories to explain this. For example, one possible result of too much exercise is a luteal phase defect.

The luteal phase is the time between ovulation and your next period and it usually lasts between 12 days and 16 days. A shorter luteal phase due to excess exercise can interfere with the ability to get pregnant because it causes progesterone levels to drop. Normally, progesterone levels remain high in the luteal phase, allowing a nice thick cosy endometrium (womb lining) to build up, which is the perfect home for a fertilized egg to implant in. However, low levels of progesterone can shorten the luteal phase. This results in a thinner endometrium which impedes successful egg implantation.

Another explanation 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 regular ovulation.

In summary I recommend women TTC (trying to conceive) to do a blend of yoga, jogging (HR below 76% of max), pilates, walking and swimming. If you enjoy strength training and HIIT, dial down the intensity, length of session and the amount of weight. Your body and future baby will thank you for it.


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