Pregnancy exercise guidelines: How should pregnant athletes train?

It’s outdated to think pregnancy is a time to avoid doing any physical activity or strenuous exercise. Just like exercise being great for your health when not pregnant, it is great for you and your baby’s health when pregnant.

James de Lacey

By James de Lacey
March 8th, 2022 | 1 min read

Pregnancy exercise guidelines

Pregnancy can be the most self-aware time of a woman’s life: “Can I eat this?” “Will I damage my baby doing some squats?” 
Some expectant mothers have a fear of exercise, but that likely stems from out-of-date recommendations that heavily discouraged exercise due to concerns of pregnancy complications.

How times have changed. The Canadian guidelines for exercise and pregnancy state ‘pregnant women should accumulate at least 150 min of moderate-intensity physical activity each week’ while the American College of Obstetricians and Gynecologists (ACOG) states ‘women with uncomplicated pregnancies should be encouraged to engage in aerobic and strength-conditioning exercises before, during, and after pregnancy.’ 
Importantly, physical exercise can help with some common discomforts and even prepare one’s body for labor and delivery. 
As my wife and I are currently starting the process of babymaking, we want the best for our future child. Since you’ve stumbled across this article, I assume you are no different.

So, I’ve done a deep dive into the research behind exercise and pregnancy and I’m going to answer your burning questions.

As long as you keep safe, exercising is great for you and your baby

How does exercise affect pregnancy?

Resistance training is probably the most controversial topic within exercise and pregnancy. Many avoid it in fear of miscarriage or potential birth defects. But does the evidence stack up?
The Canadian and ACOG guidelines recommend incorporating resistance training and aerobic training activities for greater benefits. But what are these recommendations based on?
Firstly, for those who don’t exercise, the heavier you are during pregnancy, the heavier your newborn is likely to weigh. Even your body weight before pregnancy can influence your newborn’s weight. This means the heavier you are, the more likely your child is to be born overweight. This has negative health implications for your newborn, as being overweight or obese as a child increases their chance fivefold of becoming obese as an adult. This relationship, interestingly, does not seem to exist in those who exercise regularly, which means even if you are overweight, you can benefit from exercise.

However, it is not all doom and gloom! Light resistance training combined with an eight-minute, light cardiovascular warm-up and cool-down just three times per week during the second and third trimester is enough to attenuate these effects. And I’m not exaggerating when I say light – I mean arm and leg circles with some basic exercises like biceps and hamstring curls.

A study with newborns and their mothers showed resistance exercise did not affect the type of delivery at birth or the childbirth time, with no adverse effect on the baby’s overall health.

Even those who exercised regularly (2-3 sessions per week) had highly favourable birth outcomes compared to medium (1-2 sessions per week), low (0-1 session per week), and no exercise groups when mainly performing resistance training.

Don’t like lifting weights? Well, moderate aerobic exercise just three times per week throughout pregnancy is enough to reduce the rate of caesarean birth by approximately 7%. Further, very light exercise has been shown to reduce the odds of having a large newborn by 31% without increasing the risk of having a small newborn.

So it seems combining both aerobic and resistance exercise gives you the best chance of improving your and your baby’s health. This has been shown to have better birth outcomes than performing aerobic or resistance training in isolation.

Exercise, mothers’ health and pregnancy outcomes

Exercise is about more than just the baby’s health. We must also take into consideration the mother’s health, as a healthy mother will increase the chances of a healthy baby not just at birth, but likely through childhood. Postnatal depression can be a problem some mothers face after giving birth.

It seems physical exercise can help you cope with fatigue by increasing the feeling of emotional comfort, while relaxation techniques can help battle anxiety and depression. Quality of life is also improved in pregnant women when performing any form of exercise, even yoga.

This extends past a positive outlook on life. Exercise also changes the way you perceive yourself. Many women report feeling negative about their bodies during pregnancy. But exercise has been shown to improve the way women perceive their health and even reduce the amount of weight gained during pregnancy.

How much is too much?

The amount of exercise you should perform comes down to how active you usually are. For sedentary mothers, light aerobic and resistance training is enough to provide positive benefits for you and your baby.

For those who are seriously into health, fitness, or competitive sport, your ceiling for exercise during pregnancy is much higher without any adverse effects to your unborn child. But remember, this is not a time to be trying to set new PBs.

When well-trained pregnant women (three of these women were among the five best in the world for their respective endurance sports, while others were either physically active on average for the past 12 years or competed at a national level) were split into a high or medium-volume training group, no adverse risks were found to the mother or child when compared to a non-exercising group. High training volume was 8.5 hours per week whereas medium volume was six hours a week of combined resistance and aerobic training. Interestingly, these women completed 1.5 hours per week of aerobic interval training at heart rates between 170-180 BPM. According to the Canadian pregnancy guidelines, vigorous exercising heart rate should be between 142-162 BPM for women 30+ and 147-169 BPM for women under 29.

It seems if you are well-conditioned before pregnancy, performing your normal exercise routine with high-intensity aerobic training at relatively high heart rates may have no adverse effects on childbirth. However, seek advice from a professional before embarking on such a program.

Aerobic exercise guidelines

These heart rate guidelines are taken from the Canadian guidelines for physical activity for pregnancy:
Age: <29
Light intensity: 102-124 BPM
Moderate intensity: 125-146 BPM
High intensity: 147-169 BPM
Age: >30
Light intensity: 101-120 BPM
Moderate intensity: 121-141 BPM
High intensity: 142-162 BPM

What if you don’t normally exercise?

Maybe your daily routine doesn’t involve much exercise but trying to conceive or being pregnant has inspired you to start. Better late than never!
There is very strong evidence backing exercise while pregnant, even if you were sedentary beforehand. When previously sedentary women performed light cardiovascular and resistance training exercises during the second and third trimesters, the newborn’s birth size was not affected.

It seems previously sedentary women can also partake in a vigorous exercise program (one-hour sessions with heart rates up to 150-156 BPM) without any negative effects to the unborn child. However, I would advise this should be a gradual increase in exercise intensity and not a day one workout. Consult with your health professional before deciding to increase the intensity of your training.

How do you know when to stop?

These are the warning signs to stop exercising immediately while pregnant:

  • Dizziness
  • Shortness of breath before exercise
  • Headache
  • Chest pain
  • Muscle weakness
  • Calf pain or swelling
  • Preterm labour
  • Reduced foetal movement
  • Amniotic fluid leakage
  • Vaginal bleeding
  • Can you still play sports while pregnant?

    This is going to depend on the sport and what physical activity you participated in prior to being pregnant. For example, contact sports, skydiving, horse riding, skiing, high altitude hiking, and scuba diving are activities to avoid when pregnant.

    Elite-level athletes have competed in their sport while pregnant with no ill effects. For example, Serena Williams won the Australian Open two weeks after finding out she was pregnant. Kerri Walsh Jennings won her third gold medal in beach volleyball at the London Olympics. Alysia Montano, with one of the biggest baby bumps of all, ran the 800m in the US National Track & Field championships.

    Based on these examples and the research presented, it seems high-level exercise may not be as dangerous as was once thought – it all depends on what you are used to doing for physical activity (if you are a sedentary woman expecting a baby, then starting a full-time training regime for a track event is not a good idea)!

    Other considerations

    Unfortunately, where you live in the world can have an impact on what you should and shouldn’t do. So here are a couple of safety precautions from the Canadian guidelines for physical activity during pregnancy:

  • Avoid exercising in excessive heat, especially with high humidity.
  • Avoid exercise at high altitudes (>2500m) especially if you live below this. If you live >2500m, consult your OBGYN or health professional.
  • Is it safe to lift weights while pregnant?

    Based on the research presented above, it is very safe to lift weights while you are pregnant. But here are some practical recommendations so you can get the most out of your training while avoiding any negative outcomes:
    Practical recommendations
    First, make sure you get medical clearance from your physician to ensure you don’t have any complications that could potentially be exacerbated by physical activity.

    If you are already a super fit mum-to-be, the current guidelines suggest continuing with your normal exercise routine, even if it is high volume and intensity, as it poses no adverse risks to yourself or your unborn baby. So get after it! 
    However, the goal of exercise during pregnancy should be to maintain a reasonable level of fitness, not optimise it. Here are the general and more specific guidelines for resistance training and pregnancy promoted by researcher Brad Schoenfeld:

  • 3x a week of full-body training.
  • Intensity less than 70% 1RM to reduce the risk of injury from increased joint looseness and control.
  • Static exercises (like planks) are not to be performed until you can no longer hold the position.
  • Avoid the Valsalva manoeuvre (creating abdominal tension while holding your breath). Breathe in during the lowering phase, and out during the upwards phase.
  • Control the repetition speed. Count 2-3 seconds lowering the weight and 2-3 seconds raising the weight.
  • Exercise after meals to avoid hypoglycemia (low blood sugar).
  • The Canadian guidelines for physical activity during pregnancy also recommend:

  • Accumulating 150 minutes of moderate-intensity exercise each week.
  • Three days per week minimum, but being active every day is recommended.
  • Combine both aerobic and resistance training.
  • Adding yoga and gentle stretching may also provide added benefits.
  • Kegel exercises can be performed daily – strengthening the pelvic floor through kegel exercises is important to prevent urinary incontinence which can impair quality of life while pregnant.
  • It’s important to note that if you want to participate in organised group fitness classes, you may be required to complete a physical activity readiness form like the PARmed-X for pregnancy with a healthcare professional. This will ensure you are deemed medically fit to participate in your favourite sessions.

    A semester-by-semester guide

    First semester

    No exercise modifications are necessary in the first trimester. Continue your training program as usual. However, take cautionary measures to reduce the risk of hyperthermia by wearing loose-fitting clothes and making sure your training environment is cool.

    Generally, avoid ballistic exercises such as jumps and the Olympic lifts.

    Second and third trimesters

    The second and third trimester is where significant weight gain around the midsection occurs, which means you need to modify how you exercise.

    Firstly, avoid the position lying on your back as it can obstruct blood flow from the uterus.

    Secondly, avoid forward hip flexion (e.g. Romanian deadlift or bent-over row) as the added midsection weight can make these movements uncomfortable and increase stress on the lower back. These movements can also cause dizziness.

    Finally, avoid overhead movements – replace them with isolated exercises such as lateral raises.

    Summing up

    No longer do we need to think of pregnancy as a time to avoid doing any physical activity or strenuous exercise. Just like exercise being great for your health when not pregnant, it is great for you and your baby’s health when pregnant. So time to start hitting the weights and some cardio (safely, of course)!

    James de Lacey

    James de Lacey

    James was the Head Strength & Conditioning Coach for the Romanian Rugby Union. He has previously worked in America’s professional rugby competition Major League Rugby with Austin Elite and the NZ Women’s National Rugby League Team. He is a published author and has completed a MSc in Sport & Exercise Science from AUT, Auckland, NZ.

    More content by James

    References

    1. D. Massey, J.J. Schwind, D.C. Andrews and M.W. Maneval. An Analysis of the Job of Strength and Conditioning Coach for Football at the Division II Level. Journal of Strength & Conditioning Research. 23 (9). 2009.
    2. Szedlak,M.J. Smith, M. C. Day and I.A. Greenless.Effective behaviours of strength and conditioning coaches as perceived by athletes. International Journal of Sports Science and Coaching. 10 (5). 2015.
    3. N. Radcliffe, P. Comfort and T. Fawcett. The Perception of Psychology and the Frequency of Psychological Strategies Used by Strength and Conditioning Practitioners. Journal of Strength and Conditioning Research. 27 (4).  2013.
    4. Kerr. Legacy. Constable: London UK, 2013.
    5. Triplett and G. Haff. Essentials of StrengthTraining and Conditioning. Fourth edition. Champaign, IL: Human Kinetics, 2016.

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