Intense Exercise and Pregnancy

Benefits of Exercise

In general, exercise is an essential element of a healthy lifestyle and is encouraged during pregnancy as a component of optimal health. Women who frequently engaged in high-intensity aerobic activity or who were physically active before pregnancy can continue these activities during and after pregnancy. Studies show many benefits: it reduces the risk of excessive weight gain, preterm birth, low birth weight, risk of C-section and developing diabetes and high blood pressure during pregnancy. Additionally, physical activity can also help with the aches and pains of pregnancy and reduce the risk of postpartum depression. Concerns that physical activity may cause miscarriage, preterm delivery or growth problems have not been proven for women with uncomplicated pregnancies.

While exercise during pregnancy is associated with minimal risks, some changes to your routine may be necessary because of normal body changes during pregnancy. Consult with your healthcare provider to determine if/how you need to adjust your exercise routine. This is even more important for women who have pre-existing health conditions.

Level and Duration of Activity

It’s important to listen to your body during pregnancy. Every pregnancy and every pregnant woman is different. The body goes through many changes during pregnancy: blood volume increases, your heart pumps harder, heart rate increases and aerobic capacity (fitness level) decreases. Additionally, many women experience nausea and fatigue throughout their pregnancy making it difficult to maintain prior exercise levels, not to mention proper nutrition and hydration. Listen to your body and don’t push it past its limits.

It’s difficult to compare vigorous/strenuous exercise between individuals. Jogging 10 miles may seem like a piece of cake for a marathon runner but could be extremely difficult for an Olympic lifter. For this reason, ‘vigorous’ activity is most frequently defined as up to 85% of capacity. While maximum effort is difficult to measure, capacity is often described in terms of maternal heart rate.

Another way to check your intensity level is the “talk test.” If you’re breathing hard but can still have a conversation easily—but you can’t sing—that’s moderate intensity. An activity would be considered vigorous if you can only say a few words before pausing for a breath.

If you were in the habit of doing vigorous-intensity exercise or were physically active before your pregnancy, vigorous exercise appears to be ok for most healthy women. However, there is limited information on individuals who exceed the accepted 85% capacity and an upper level of ‘safe’ exercise intensity hasn’t been established.

In general, it is recommended to exercise 30-60 minutes 3-4 times a week to up to daily.

What to Consider When Exercising

• Stick with what your body is used to. If you are used to long-distance running, pregnancy is not the time to turn into a power lifter and vice versa.
• Stay hydrated. Drink plenty of fluids before, during and after exercising.
• Avoid overheating. Even if you are used to exercising in 90-degree heat with 70% humidity, you may have to look for an alternative method such as air-conditioned gyms. Don’t use steam rooms, hot tubs, and saunas.
• Avoid exercises that call for you to lie flat on your back in the second and third trimester of your pregnancy because this allows less blood flow to your womb.
• Don’t engage in sports where you could fall or get injured, or sports where you might get hit by a fast ball.
• Reduce weight load. There is limited data on the effects of resistance training (e.g. weightlifting) on pregnancy. There is a concern that holding your breath during heavy lifts can possibly result in baby’s heart rate slowing down. Because of this, you may have to reduce the resistance load.
• Allow enough time for your body to recover after each training session.
• Make sure you have enough caloric intake. If you regularly participate in vigorous-intensity exercise, you will likely have to adjust your caloric intake to allow for appropriate weight gain for your pregnancy.
• Continue to fuel your body. Prolonged high-intensity exercise can result in low blood sugar. Make sure you fuel your body if you plan on exercising over 45 minutes.
• Check with your healthcare provider before continuing any supplements such as pre-workout protein shakes. Also, see our MotherToBaby blog on this topic.
• Stop exercising if you feel dizzy, have a headache, develop chest pain, have calf pain or swelling, have muscle cramps, or you experience vaginal bleeding, leakage of fluid, contractions or shortness of breath before exertion. Call your healthcare provider with any concerns.

Postpartum and Breastfeeding

In general, exercise can be resumed gradually after delivery as soon as it is medically safe – consult with your healthcare provider on when they may be. This may depend on mode of delivery (c-section vs. vaginal birth) and any additional health problems or complications. When exercise can be resumed varies among women, with some being able to start exercising within days after delivery.

Regular exercise has not been shown to affect breast milk production or quality and hasn’t been shown to affect baby’s growth either. It is extremely important to remain hydrated during breastfeeding, especially when regularly exercising. All women who are breastfeeding should also focus on the correct amount of caloric intake which may vary depending on level of activity.

Bottom line is, we are all different athletes and will all have different needs during pregnancy and the postpartum period. There is no ‘one-size-fits-all’ recipe for vigorous exercising during pregnancy. The best things you can do are to consult with your healthcare provider frequently and listen to your body. For more information, see our MotherToBaby Fact Sheet on exercising. You can also find some information on which foods/drinks to limit/avoid, the appropriate amount of weight to gain, and the recommended amount of exercise here.

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