Not everyone is a “Fertile Myrtle”… the endearing term we OB-GYNs often give to those women who get pregnant in…
Fortunately, we know that exercise in pregnancy is highly beneficial to mom and baby. Barring any complications or contraindications, you should be exercising in pregnancy for best health and outcomes.
But, how hard should you be exercising in pregnancy?
And, more specifically, should you be exercising with higher intensity interval training (HIIT) in pregnancy, or keeping exercise at a low to moderate intensity level for all workouts?
The main thing to consider when exercising in pregnancy are the risk vs. benefits. In pregnancy, we need the benefits to significantly outweigh the risks.
You could argue there’s some inherent risk with any exercise, regardless of how ‘perfectly’ it’s programmed. I would argue, there’s greater risk with not exercising.
That being said, I do believe that women can successfully and safely use higher intensity exercise and metabolic conditioning type work in pregnancy. The only catch is that it must be programmed and planned strategically.
This isn’t just about throwing some treadmill sprints in at the end of a workout. Or, working kettlebell swings, burpees, and jump squats into a circuit because they get your heart rate up.
We need to work differently to support your body and your baby. So, how do we do that?
Is there a specific heart rate you should not be exceeding while exercising in pregnancy?
Truth be told, with the data we have available to us now, there are no hard and fast heart rate guidelines. Heart rate limits used to be imposed, but now they are rarely used.
While you can absolutely track your heart rate using a monitor throughout workouts, and it’s pretty interesting to do so, you don’t need to worry about keeping your heart rate below the previously recommended 140 beats per minute, if you feel comfortable raising it higher than that.
Rate of Perceived Exertion (RPE) is a better means of monitoring your exercise intensity.
During your higher intensity intervals, you’ll likely want to keep your work time rate to a 7/10.
1 = lying on the couch
10 = sweating profusely, can’t talk, completely out of breath
This means that you can absolutely work at a challenging rate, a “somewhat hard to hard” level. You won’t want it to feel very hard or very, very hard, though.
You’ll be a bit breathless, can speak, but will feel like your breathing rate and heart rate are increased.
Keep in mind, during pregnancy it’s normal to feel more breathless upon exertion, so this rate is relative to how you are feeling NOW, not what you used to do when not pregnant.
Body temperature is something you’ll want to be aware of during higher intensity exercise. There is concern that high body temperatures could cause birth defects, especially in the first trimester.
It’s generally recommended to keep your body temperature under 100 degrees Fahrenheit or 38 degrees Celsius.
Be cautious of exercising in extremely hot or humid climates; stick to indoor exercise if you do live in an area that qualifies and are doing higher intensity work.
Make sure you are well hydrated during exercise. Keep your fluid intake between 500ml – 1L (~16-32 oz.) during workouts to remain well hydrated.
You can certainly be sweating during exercise, but I wouldn’t recommend working to the point where you’re pouring sweat, especially if you’re in an air-conditioned gym.
Higher intensity interval training may not be the most optimal form of exercise to include in your first trimester.
This is due to a variety of reasons, including the concern of overheating, potential sickness, nausea, fatigue, reduced caloric intake due to food aversions, and just the general feeling of caution many women tend to experience while in their first trimester.
For my clients, I recommend sticking to a more traditional strength training type program during the first trimester, especially when a woman isn’t feeling quite herself for weeks at a time or is just getting into exercising consistently.
The second trimester tends to be a good time to introduce more metabolic conditioning. Many women tend to start feeling more like themselves, fatigue could be lessening, and they have a bit more energy in workouts.
If you were not exercising consistently in the first trimester, give yourself a good month of consistent strength training workouts at this time before adding much in the way of metabolic conditioning.
You can definitely continue along through the third trimester with the higher intensity intervals.
Keep in mind how your breathing and your body feel, though. You might start to feel more out of breath—simply adjust the intensity appropriately. Remember, the rate of perceived exertion is how you’re feeling now, not how you were feeling last month.
Notice how you feel in the core and pelvic floor with the growing belly. If you have pelvic pain or pressure, or back pain adjust the exercises you’re using or simply slow down.
You’ll likely want to back off or reduce the time you spend doing interval work as you get further into the last four to six weeks of pregnancy, as fatigue might ramp back up.
High impact and plyometric type exercises should generally be avoided in pregnancy, especially as you become further along in pregnancy. (Yes, this includes running!)
Here’s why: the downward pressure on the pelvic floor from the increasing size and weight of the uterus, placenta, fetus and normal weight gain of pregnancy can be difficult enough for the pelvic organs (bladder, uterus, rectum) to endure.
Plus, we have hormonal considerations to factor in, such as the increasing levels of relaxin that is working to make the soft tissues of the body more lax to help with labour and delivery.
These factors do not need to be compounded by the additional stress of running, jump squats, and burpees. The good news? You don’t need these exercises to stay fit or to challenge your fitness level.
You can use higher intensity interval training as a stand-alone workout, or at the end of your workout. You could perform your interval training between one and three times per week.
Keep the duration of your intervals between 5 to 20 minutes of combined work and rest.
Rep ranges can be from 10 to 15 and timed intervals from 15 to 30 seconds. Be sure to take adequate rest time between exercises and sets.
Rest time between exercises could be up to 30 seconds (or more if you need it!). The rest time between sets should allow you to recover fully before starting your next set so you feel strong and ready to work at the higher intensity again. You can use 1:1, 1:2, or 1:3 ratios for your work:rest time.
For example, if your work time is 1 minute rest for 1 to 3 minutes between sets.
Really, just take as much time as you need to feel recovered and ready to work again. Don’t rush. Allow the heart rate to come down to a more normal level before bringing it back up again.
With my ladies, I use supersets, tri-sets, and quad-sets to work in metabolic conditioning.
1A. Hip thrust: 30 seconds
1B. Incline treadmill walking: 30 seconds
This is typically the best way to get into and out of hip thrusts during pregnancy:
2A. Bodyweight squat: 15 reps
2B. Inverted row: 15 reps
1A. Battle ropes: 15 to 20 seconds
1B. One-Arm dumbbell chest press: 10 to 15 reps
1C. Dumbbell/kettlebell sumo deadlift: 10 reps
Note: You’ll likely want to swap the deadlift for a different bridging or hinging movement once you’re further into your second trimester or into the third trimester depending on how the core is functioning.
2A. Sled push walking (handles high) or sled pulling: 20 to 30 seconds
2B. Inverted row: 10 to 15 reps (see the video above)
2C. Hip Thrust: 10 to 15 reps (see the video above)
If you are pushing the sled use the high handles and stay as upright as possible. This is how you can pull the sled, if it feels more comfortable to have the belly not facing the ground (from 25 seconds on):
1A. Sled push walking (handles high) or sled pulling: 20 to 30 seconds
1B. Seated Cable Row: 10 to 15 reps
1C. Bodyweight Squat: 10 to 15 reps (see video above)
1D. Side plank: 10 to 20 seconds each side
You can take side plank from the knees or feet, as demoed in this video:
2A) Battle Ropes: 15 to 20 seconds
2B) Incline DB chest press: 10 to 15 reps
2C) Reverse Lunges: 8 to 10 reps
2D) Inverted Row: 10 to 15 reps (see video above)
You can do reverse lunges with your bodyweight or add dumbbells:
As always, really pay attention to how you feel in your body during this type of training. If you feel strong, can breathe well, and don’t feel discomfort, you’re good to keep going. If you feel discomfort at all, dizziness, or like you’re working beyond a 7/10, it’s best to rest.
There are so many myths about exercising during and after pregnancy, it can be hard to know if you’re doing the “right” thing. Our education materials are carefully vetted by OB/GYNs, PhDs, Registered Dietitians, Women’s Health Physiotherapists, and Pre and Postnatal Exercise Experts, and we have put together this FREE handbook where you’ll learn: