Does Exercise Boost Fertility?
Research suggests that exercising in moderation, 3-5 times per week for 30 minutes to an hour has benefits for fertility - as long as you are consuming enough healthy calories to prevent an energy deficit.
In this article we'll cover why and how exercise impact fertility, and guidelines around activity levels and types of exercise research suggests are best for balancing hormones.
Key takeaways:
Exercise moderately 3-5 times per week for 30-60 mins
Take rest days and avoid intense exercise of long duration.
Gently build up to increases in intensity, duration and frequency.
Make sure that you eat sufficient (healthy) calories for your level of physical activity.
If you’re not already exercising, introduce it gradually to give your body time to adapt, to avoid injury and increasing oxidative stress.
Avoid heavy lifting, exposure to high temperatures, and any torsional activity, especially during fertility treatments or when trying to conceive.
Enjoy calming and restorative exercises like walking and yoga, which will improve mood and reduce stress.
Remember to run your exercise plans past your doctor, in particular if you are very active or if you are going to start introducing physical activity after a period of being sedentary.
How does exercise affect fertility?
Moderate exercise can help improve blood flow to your reproductive organs, improve antioxidant defenses, reduce excess body fat, help manage insulin levels, moderate stress hormones, counter anxiety and depression and enhance the quality and quantity of sleep.
All beneficial things for fertility outcomes!
Improves blood flow to your reproductive organs
One of the things your doctor will assess on ultrasounds of your ovaries is blood flow. That’s because good, oxygen-rich blood flow is vital for the growth process of the follicles that contain your maturing eggs.
Good circulation is thought to have a positive effect on egg quality and success rates in ovarian stimulation. Experimental data has linked the number of eggs retrieved and the quality of eggs retrieved to ovaries with good blood flow and several studies have found embryos with the highest implantation potential originate from follicles that are well-vascularized and oxygenated.
Reduces oxidative stress
Intense exercise generates free radicals.
But when you exercise in moderation, your body’s antioxidant levels rise in order to moderate the damaging effects of free radicals and to protect against future attacks, particularly within the ovaries.
Reduces excess body fat
People who are overweight (BMI of 25–29.9) or obese (BMI of 30+) have predicted pregnancy rates 30% - 75% below that of women who are not.
This is thought to be due, in part, from the fact that excess body fat can lead to hormonal imbalances.
Helps manage insulin
High blood sugar and insulin levels can significantly decrease both the quantity and quality of eggs retrieved in your egg freezing cycle.
But research shows that moderate exercise can help improve insulin sensitivity and glycemic control.
If you fall into the obese category, even a modest session of exercise is shown to improve insulin sensitivity into the following day.
Moderates stress hormones
Moderate exercise can help you manage stress, which is interlinked with hormones like cortisol (which we will review in detail in the <Stress> chapter).
Elevated cortisol over prolonged periods (chronic stress) can interfere with normal reproductive hormones and thus impact the egg maturation process.
Promotes better sleep
Engaging in low to moderate intensity exercise can help you improve both the quality and quantity of your sleep, especially if you suffer from chronic insomnia.
A meta-analytical review of 66 research studies revealed that even just one one moderate workout session can increase total sleep time, reduce the time spent getting to sleep, increase overall sleep efficiency, and can increase the amount of REM sleep you get at night.
This is important, because getting sufficient good quality sleep has a host of reproductive benefits.
Questions to ask yourself:
1. Are you over-exercising?
When it comes to your fertility, there can be such a thing as too much of a good thing.
Strenuous exercise is defined as at least thirty minutes of intense activity and close to the limit of muscle contractile activity.
What counts as very frequent exercise to the point of 'over' exercising? If you are physically active most days, that could make you over three times more likely to experience fertility problems than women who are sedentary, according to Norwegian researchers who studied the exercise habits and reproductive systems of nearly 4,000 women.
And, exercise duration seems to make a difference; if you exercise for over 4 hours a week for a sustained length of time.
In a US-based study of women undergoing IVF, frequent exercisers were almost three times more likely to have to have their whole IVF cycles cancelled due to their bodies not responding well to the treatment.
Extreme exercise can have a negative effect on your fertility, especially if you have a BMI of 19 or under or if you are suddenly increasing the duration, frequency or intensity of activity.
If this applies to you, increase the number of rest days in your exercise schedule and make sure not to up level too suddenly.
The effect on fertility is not necessarily dependent on how much you exercise, but how much you do relative to your current ability level.
Researchers don’t know the exact reason for this, but they think it could be partly down to intense exercise triggering excessive oxidative stress.
Oxidative stress is an imbalance between free radicals and antioxidants in your body and it is associated with impaired fertility.
Exercise, by its very nature, is an oxidative process in which free radicals are generated - it’s a side product of how our muscles move.
When you exercise moderately, the body generates adequate antioxidant defenses to protect itself.
The trouble is, when you exercise to the extreme, be that aerobically (such as marathon running) or anaerobically (such as lifting heavy weights) the body can’t keep up strong enough defenses and oxidative stress builds.
The extent of which depends on the exercise duration, intensity, fitness condition and your individual nutritional status.
2. Are you active enough?
Scientific and medical consensus is that moderate exercise has benefits, but 77% of Americans do not get enough exercise.
One study found that women who exercised 30 minutes or more a day had a reduced risk of ovulatory infertility than those who seldom exercised. This is especially true for women who are overweight.
3. Are you adequately fuelling your workouts?
We are at risk of reproductive issues if we don’t eat enough calories through food (i.e. energy) to support the amount of calories being expended through exercise and other necessary functions like walking and digesting food.
“Energy availability” is the key to fertility friendly workouts. That refers to the amount of energy left over and available for your body’s functions after energy has been used for training.
More than thirty years of studies have shown that women who do lots of exercise without adequate nutrition and caloric energy to support it are at increased risk of reproductive problems.
Researchers have mostly studied women who do sports/activities wherein having a low body weight or lean physique is intertwined with success.
For instance, studies have found that up to 79% of ballet dancers, runners, figure skaters and gymnasts report menstrual irregularities.
One month with a large drop in energy intake could have knock-on negative effects on your reproductive hormones.
Energy deficiency affects fertility because important reproductive hormones stop being produced when there isn’t enough available energy to sustain them.
It’s also important to note how sensitive our bodies are to energy deficits.
Even energy deficits garnered over one day have been shown to have adverse effects on hormone concentrations - so skipping meals even for a few days can start to have an impact.
The key is to make sure to consume more healthy calories (energy) than you expend throughout the day in order to avoid an energy deficit.
More than thirty years of studies have shown that women who do lots of exercise without adequate nutrition and caloric energy to support it are at increased risk of reproductive problems.
And don't suddenly increase exercise - work up to it
Scientists think sudden increases in the amount or intensity of exercise you do could also be bad for your reproductive health.
So signing up for a marathon or joining Barry’s Bootcamp can be fine as long as you gradually increase your fitness and activity levels rather than jumping right in multiple days a week for a real beasting.
Give your body time to adjust: heavy exercise in untrained women provokes “significant increments in ovarian hormones,” whereas no such increases were observed in women who regularly train when they were monitored doing the same heavy exercises.
What are the best exercises for fertility?
Any exercise that increases your heart rate can improve circulation and blood flow to the ovaries.
Daily activities such as walking or riding a bicycle strengthen and enlarge the heart muscle, improving the pumping efficiency.
Increased circulation does not require intense exercise.
A recommended level to aim for and build up to is cardio for 30 minutes a day, 3 times a week with 2 x 30 minute moderate strength training sessions and additional restorative yoga or stretching.
Moderate exercise means a 5 or 6 out of 10 in the level of effort you’re putting in during a workout.
At that level, you’ll feel a noticeable increase in breathing and heart rate. You should be able to talk but not sing.
Exercise moderately 3-5 times per week for 30-60 mins
“Moderate exercise” is usually defined as a 5 or 6 out of 10 in the level of effort you’re putting in during a workout. At that level, you’ll feel a noticeable increase in breathing and heart rate. You should be able to talk but not sing. You’ll know you’ve gone out of the “moderate” range if you can only say a few words without stopping for breath.#
Any exercise that increases your heart rate can improve circulation and blood flow to the ovaries. Daily activities such as walking or riding a bicycle strengthen and enlarge the heart muscle, improving the pumping efficiency. Increased circulation does not require intense exercise (in fact, sticking to low impact movements during the medication phase is essential.)
A sensible level is cardio for 30 minutes a day, 3 times a week with 2, 30 minute moderate strength training sessions and additional gentle yoga, stretching or meditation.
Which exercise is best for fertility?
While there is limited research on exactly which types of exercise are better or worse for your fertility outcomes, there are a few physical activities regularly recommended by fertility doctors because they require moderate exertion and can be adapted to your own fitness level:
Brisk walking
Dancing
Light aerobics
Leisurely bike riding or stationary bike
Light jogging
Swimming
Pilates
Hiking
Leisurely tennis
Stretching
Light elliptical
Yoga (not including Bikram or hot yoga)
Exercises to avoid for fertility and pregnancy
Avoid activities and exercises with high heat if you're trying to conceive or think you could be pregnant
There is some research indicating that exposure to high heat during pregnancy can cause issues like birth defects.
Despite a lack of definitive research, many doctors advise against activities that involve extreme heat (such as hot yoga, steam rooms and saunas) as a precaution.
Minimize heavy lifting
According to researchers, women seeking fertility treatment whose work included heavy lifting (such as nurses or interior designers) produced 14% fewer eggs than women who did not, and those that were produced were of a poorer quality.
It's speculated that this could be due to the stress such repetitive physical exertion puts on the female body and its ability to reproduce.
It’s not just jobs that involve heavy lifting, of course...weight training and cross training sessions like CrossFit can fit into this category.
If you’re a gym bunny, keep active, but now is probably not the time to start lifting iron.
Taking up a marathon or other intense endurance training
Research has shown that after running a marathon, oxidative DNA damage lasts for more than a week after the race.
If you're already a pro or keen runner, the situation will be different than for people with general fitness levels - but always check in with your own doctor.
Exercise routines during fertility treatments
Before IVF or egg freezing, the hormones you’ll inject over the 2-3 weeks prior to egg retrieval are likely to cause bloating, cramping and other PMS-like symptoms such as fatigue.
As such, it’s unlikely you’re going to feel like being super active but it shouldn’t stop you from enjoying light exercise like a walk or meditative yoga.
Avoid heavy lifting and torsional twists
Intense, twisting or heavy-lifting exercise puts you at risk of ruptured cysts, discomfort or, more rarely, ovarian torsion.
Doctors recommend during this time is no torsional (twisting) or aggressive exercise, as this could place your already swollen ovaries under additional strain and increase the likelihood of complications.
Avoid martial arts/contact sports
Again, to minimize the risk of ruptured or twisted ovaries, doctors recommend avoiding these during fertility treatments - that's especially true if you are trying to get pregnant right away!
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