Exercise and Fertility

Exercise has so many benefits for the body and mind, from relaxation and stress reduction, to improvements in metabolic markers and general health, so exercise should always form part of our daily routine. You can find more about exercise and why it is so important for fertility and preconception care in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy. In this section, we give an overview of:

• Exercise and female fertility
• Is too much exercise bad for fertility?
• Personalising exercise for fertility and pregnancy
• Exercise for pregnancy
• Exercise and male fertility
• Exercise for weight loss and metabolic health
• Interval training
• Weight-bearing exercise
• The benefits of morning exercise
• Exercise across the menstrual cycle
• Take-home message

Exercise and female fertility

Being physically active is important for fertility and pregnancy, but people tend to overestimate what is good for them for fertility and underestimate what is best for pregnancy. However, remaining physically active during pregnancy improves outcomes, maternal health and the health of the baby. Staying physically active is also associated with better mental health, and this is vital for pregnancy and after the birth to protect against the possibility of postnatal depression. Exercise has been shown to improve underlying features and symptoms of polycystic ovary syndrome (PCOS). So we advise starting a programme of exercise while trying to conceive that you can safely sustain during pregnancy. Studies indicate that mild to moderate exercise that includes a mixture of low- or medium-intensity cardio with weight-bearing exercise is best for women trying to conceive.

Spending too long sitting down is also associated with adverse health outcomes and poor metabolic function, including type 2 diabetes, being overweight, coronary heart disease, some cancers and even premature death. Studies looking at workplace exposures and male fertility also show an association between jobs that involve long periods sitting down and reduced male fertility.

Short bouts of exercise do not compensate for a sedentary lifestyle, so don’t let sessions at the gym become the only active part of your day. Aim to get up from your desk at least every 15 minutes, take the stairs and walk to work where possible (taking a route that minimises exposure to air pollution). Walking is an excellent antidote to excess sitting, so even short, regular walks will make a difference. If you have a very inactive day, these small habits can help to mitigate the negative effects of all that sitting, and will have a positive impact on metabolism and, as a consequence, fertility.

Is too much exercise bad for fertility?

As a general rule, the evidence suggests that women should aim for mild to moderate activity that can be started while trying to conceive and safely sustained during pregnancy. Intuitively, we can sense what may be good for us during pregnancy, as the female body has to carry a developing baby and keep him or her safe for 9 months. There is a sweet spot that means keeping fit without putting too much of a strain on your body, especially your core. You should aim to be generally active on a daily basis including activities such as walking, gardening, lifting shopping, and taking the stairs rather than the lift, and do at least 30 minutes of more vigorous exercise such as gentle short-distance jogging, brisk walking, swimming, cycling, and dance or gym classes that raise your heart rate three times per week. In addition, weight-bearing exercise three times per week is also important. This could be yoga, pilates, tai chi or step classes, gentle weights, hiking in hilly terrain, or using the rowing machine or cross-trainer in the gym. You can do a combination of exercises at home that do not require any special equipment: squats, lunges, running up the stairs and single leg raises where you hold the position for a set time (increase from 10 seconds per raise) while holding a chair or table on alternate legs. This means doing some form of exercise on six days per week.

Research shows that over-exercising, on the other hand, can inhibit ovarian function, stop you ovulating and, ultimately, stop your periods. Adipose tissue (body fat) produces hormones including leptin and some oestrogen, so when your body weight and body fat percentage drops, the levels of these hormones go down. Your periods stopping can be the end-point of over-exercising, though effects are likely to kick in before you notice any significant changes, with studies demonstrating that female athletes have a higher prevalence of not only amenorrhoea (no periods) and oligomenorrhoea (infrequent periods with cycle length regularly more than 35 days), but also a greater number of anovulatory cycles (no ovulation) and a shorter luteal phase (second half of the menstrual cycle). A normal luteal phase is important in being able to sustain a pregnancy. The hormone changes that cause these differences in the menstrual cycle include lower levels of oestrogen in the early, follicular phase, lower levels of progesterone in the luteal phase, and no mid-cycle surges in hormones. A significant exception to these norms is irregular periods associated with PCOS, as this type of oligomenorrhoea can improve with exercise due to the specific features of PCOS.

You can find out more about how to decide the right level of exercise for you in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

Personalising exercise for fertility and pregnancy

While studies can guide us at a population level, you need to learn what is right for you. If you have exercised all your life, your body will be used to a higher level of activity and higher levels of exercise may not impact your fertility, as long as you have a regular menstrual cycle of no shorter than 26 days. The athlete Paula Radcliffe conceived while exercising vigorously, continued training through most of her pregnancy, and completed a 10KM charity run while 7 months pregnant. This is not something that would be advisable for most women but it is about understanding your own body and making the appropriate modifications to your regular routine. Reducing exercise from very high levels if you have trouble conceiving, however, is usually sensible as a first port of call. In a preconception phase before you start trying to conceive, we always advise patients to judge exercise based on your physical response. If you feel your heart-rate pounding, you become very red-faced, sweat excessively, are physically exhausted and take longer than three minutes to recover to normal resting heart rate, that is generally too much for good fertility.

For both fertility and pregnancy, the levels of physical activity that will result in what we call the red-faced effects in your body will vary from person to person. Having this kind of understanding enables you to personalise the evidence to you and is essential in optimising your fertility. Feeling excessively fatigued after exercise or feeling more fatigued than you used to can also be a sign of nutrient deficiencies or other health problems such as thyroid problems or onset of coeliac disease. We would always recommend getting to the bottom of any issues rather than continuing to push your body too hard, as over-exercising with underlying health or nutrient issues can be a stressor on the body. The overall effects of exercise over time should be to energise you, and if it doesn’t, pay attention and seek professional advice.

These factors highlight the vital importance of preconception care, listening to your body and preparing for pregnancy for as long as possible. Achieving a good level of fitness such that moderate exercise doesn’t cause these red-faced effects in your body and allowing your body time to get used to a particular level of activity as your own normal, while monitoring any effects on your menstrual cycle will help you achieve the best outcomes in terms of both conceiving and also carrying a healthy pregnancy. Remember that your menstrual cycle is the foundation for good fertility and it also your best barometer of how the changes you make are affecting your reproductive health and fertility. As you begin a process of change, you can expect to see some short-term changes, but over a period of months, if you are not experiencing a regular menstrual cycle with no symptoms that indicate an issue, it is time to review your programme and seek professional advice.

What is healthy will very much depend on your individual body. We can assume that Paula Radcliffe’s body is both genetically suited to and used to a very high level of physical activity, as she was able to sustain her fertility and carry a healthy pregnancy at a very high level of exercise. That is obviously one end of the spectrum. We sometimes see patients who tell us they have been advised not to exercise at all, and this is the other end of the spectrum that isn’t good for most people. Given the importance of exercise for a healthy pregnancy, this is an area definitely worth investing time and effort to get right as it will reap dividends for your health during pregnancy and the future health of your baby. A recent study showed that pregnant women need almost as much energy as endurance athletes, as well as having similarly elevated metabolic rates, so you need to get fit to prepare your body optimally! When you factor in that preeclampsia is now thought to be linked to poor cardiovascular health, exercise really does become an essential tool for everyone who is trying to conceive and going through fertility treatment.

Exercise for pregnancy

Similar rules apply for indicators of sensible levels of fertility exercise as for pregnancy exercise. For pregnancy, as well as not allowing your heart rate to go too high, measures such as keeping well hydrated and ensuring you eat enough before and after exercise are important.

The one exception to exercise during pregnancy is women who have any issues with their cervix, including past treatment for abnormal smears. Any risk of what is inappropriately termed ‘cervical incompetence’, where there is potential weakness of the cervix such that the pregnancy may be at risk with excessive or overly rigorous exercise, should always seek professional advice as to what is safe for them. This may not mean stopping exercise altogether, and brisk walking at least is usually safe for most women during pregnancy. It is also safe to exercise more in the preconception period. We recommend that, if you find yourself pregnant with this issue, you should follow advice from your obstetrician and ensure you are monitored regularly, including with ultrasound scans of your cervix and developing pregnancy. Finally, always listen to your body and reduce physical activity if you sense it is having a negative effect even if you have been told it is safe. Studies can tell us what happens at a population level, but the trick is to determine your personal risk, which is always individual to you.

Exercise and male fertility

Exercise is likely to be beneficial for male fertility and is certainly important for general male health. Sedentary lifestyles negatively impact sperm quality. One study showed that 30 minutes of moderate- to high-intensity exercise improved sperm parameters in previously sedentary men. Sperm quality link to sperm section of male fertility declined again about a week after exercise stopped; therefore it is important to maintain a programme of exercise in the long term.

Extreme exercise can have a negative effect due to increased oxidative stress in the testes, so triathletes and professional sportsmen may find their sperm is in need of some TLC. Furthermore, tight-fitting Lycra shorts may also have a detrimental effect so loose-fitting shorts or jogging bottoms are better.

Exercise for weight loss and metabolic health

Exercise is extremely important for general and metabolic health, but actually contributes much less to weight loss than changes to diet. This is because our bodies and behaviour tend to adapt in order to compensate for the additional exercise, so there is a tendency to eat more when undertaking more vigorous exercise. However, exercise has been shown to contribute more to weight maintenance after weight loss than diet, so aiming for an individualised, balanced, long-term weight-loss strategy that includes exercise is important.

Interval training

In terms of aerobic exercise, interval training can be more effective for weight loss than fixed-pace. ‘Scout’s pace’ while walking or jogging is a good example. This can be simply 30 minutes of brisk walking and breaking into a run that raises the heart rate one minute out of every ten, so your total running time is three minutes during a thirty-minute walk. Interval training can also be varying the gradient and intensity on a treadmill or cross trainer in the gym across the duration of your session.

Weight-bearing exercise

Weight-bearing exercises help build muscle tone, improve metabolic health and aid weight loss. Yoga, resistance training (including squats, lunges and stairs at home) and weight-training are all good forms of weight-bearing exercise. Muscle cells have a higher metabolic rate than fat cells (they are working harder and so use more energy) and so weight-bearing exercise is helpful for losing fat and improving metabolic health. Keeping physically active through aerobic exercise is also important, so always include some cardio.

The benefits of morning exercise

Some studies show that exercising in the morning results in greater weight loss than exercising after 3pm, so aim to do at least some exercise at the start of the day. One study showed that those who exercised in the morning were generally more active throughout the day than afternoon or evening exercisers, taking more steps in total, and also ate slightly less, and consequently lost more weight.

Exercise across the menstrual cycle

The fluctuation of hormones across the menstrual cycle results in measurable changes in metabolism, physical response to exercise and eating patterns. Oestrogen tends to improve physical performance and exercise recovery, so phases of the cycle when this hormone is at its highest are the best times to maximise exercise levels, though more research is needed and a personalised approach is best. Data is mixed on progesterone but some studies show that high progesterone levels around the time of ovulation cause metabolic changes that indicate this time may be the best for weight-bearing exercise to build lean muscle.

You can find out more about changes across the menstrual and what may be best for you in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

Take-home message

A level of exercise that is good for you is personal. If you are used to being fit and active you can usually do more and maintain good fertility. Over-exercising during a preconception phase, even when very overweight, however, may be unhelpful if you overeat to compensate. As with everything, balance is key, especially when trying to improve your fertility.

You can find out more about how to find the best balance for you in our Fertility and Preconception Care course and in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

References

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