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I recently completed the Canadian Society of Exercise Physiology’s Pre and Postnatal Exercise Specialization course. I want to share some of the information that was provided to me in hopes it provides some useful information to pregnant women who want to remain or become active over the course of their pregnancy.

Always speak to your health care provider before becoming physically active.

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The Canadian guideline recommends that all women without contraindication should be physically active throughout their entire pregnancy. This includes women who were inactive prior to pregnancy, women who are overweight or obese prior to pregnancy, and women diagnosed with gestational diabetes mellitus.

Pregnant women should accumulate at least 150 minutes/ week of moderate intensity physical activity to achieve meaningful reductions in pregnancy complications. This should be accumulated over a minimum of 3 days/ week through a combination of aerobic and resistance training, however being active everyday is encouraged.

Dose response relationships have been identified between increasing volumes of physical activity with greater reductions in the odds of developing pregnancy complications including gestational diabetes mellitus, preeclampsia, gestational hypertension, prenatal depressive symptoms, and excessive weight gain during pregnancy.

Its important to note, however, women can achieve significant health benefits even if they exercise at a low intensity and/ or below the recommended 150 minutes/ week. Some exercise is always better than none.

Target Heart Rate Zones

Examples of moderate intensity physical activity include brisk walking, swimming laps, and even some household chores like vacuuming. The target heart rate zones are as follows:

There is limited information about the impact of vigorous intensity physical activity and near maximal heart rates, so women are who wish to exercise at this intensity should consult with their obstetric care provider.

Exercise Considerations

Pregnant women should incorporate a variety of aerobic exercise and resistance training to achieve greater benefits. Yoga and gentle stretching is encouraged on top of the 150 minutes/ week. Additionally, pelvic floor muscles training such as Kegel exercises may be performed daily to reduce the odds of urinary incontinence. This type of exercise should be supervised by a pelvic floor specialist or physiotherapist that specializes in pelvic floor health.

Its extremely important that pregnant women drink plenty of water to avoid dehydration. Water is important part of ensuring that the baby has healthy growth and development. Water is vital to help form the placenta and amniotic fluid.

Pregnant women who feel light-headedness, nausea, or feel unwell when they exercise flat on their back should modify their exercise position.

Activities to Avoid

Pregnant women should avoid physical activity in excessive heat (including hot yoga), especially with high humidity. Since pregnant women have enhanced vasodilation of their blood vessels to maintain blood pressure, combined with a greater amount of blood flow to the skin when exercising in the heat can increase the risk of fainting.

Avoiding activities that risk trauma to the belly is recommended. This includes activities with a high risk of contact or falling such as hockey, soccer, downhill skiing, horseback riding, Olympic weightlifting, and riding a non-stationary bike. Scuba diving should also be avoided as there is no known safe depth for the fetus. Also, the fetal lung is too immature to filter out nitrogen which is found in the compressed air tanks used by divers. Moreover, high altitude training (unless born and raised at altitude) is not recommended as the combined impact of exercise, pregnancy, and high altitude above 2500 meters is unknown.

During pregnancy, the hormone Relaxin is released by the placenta into the circulation. This hormone slightly loosens joints and may soften other connective tissue. As a result, there is an increased risk of injury with activities that are jarring, twisting, or involve quick turns. Overstretching should be avoided as this can lead to injury of the muscle(s).

It has long been advised that pregnant women avoid the Valsalva Manoeuvre (straining or holding ones breath), as it might change blood pressure and/ or disrupt blood flow to the uterus and fetus. It also causes undue force on the pelvic floor and abdominal muscles. Avoiding crunches, sit-ups, leg raises, and other similar exercises to prevent further separation of the rectus abdominus is also recommended.

 All pregnant women should immediately stop physical activity and consult with their health care provider if they experience any of the following signs and/ or symptoms:

• Persistent excessive shortness of breath that does not subside with rest
• Severe chest pain
• Regular and painful uterine contractions
• Vaginal bleeding
• Persistent loss of fluid from the vagina
• Persistent dizziness or faintness that does not resolve after rest

Resistance Training

There isn’t a lot of information available regarding the impact on resistance training on health outcomes during pregnancy. However, not engaging in resistance exercises can cause a reduction in maximal strength by 22-24 weeks gestation. Also, there is some research suggesting that resistance training may increase connective tissue strength. This may be a beneficial modality for reducing injury risk.  

Women with resistance training experience can continue exercising at or near their current level of activity, however, modifications may be necessary. Those without experience should start gradually and being with simple exercises.

Using a higher repetition range of less than 70% of one rep max, with 10 or more reps is encouraged. This may decrease joint related stress and reduce injury risk. Sets should be performed to the point of moderate fatigue, but not to failure. Training for a specific muscle group should be performed on non-consecutive days to allow for recovery. When lifting, breath in during the eccentric phase, and breath out during the concentric phase.

Women who are new to resistance training should begin with 1 set per exercise. Intermediate to advanced individuals can perform 2-3+ sets. Emphasis must be placed on proper form and technique.  

All modalities can be utilized – free weights, machines, bands, cables, and body weight movements targeting major muscles groups. For optimal functional ability, varied exercise in all 3 planes of movement should be incorporated.

Finally, heavy lifting has not been examined, and there is no identified upper limit. If you want to engage in heavy lifting or exercise with a heart rate reserve above 80%, first speak to your obstetric care provider.

FITT (Frequency, Intensity, Timing, and Type) Principles

Aerobic

F	3+ days/ week.
I	Moderate intensity. 125-146bpms for women 29 and under. 121-141bpms for women 30 and over. An RPE of 12-14 on the 6-20 Borg Scale. The ability to talk but not sing.
T	150 minutes/ week which may be broken up in the smaller bouts of 20 minutes or less. There are benefits associated with exercise both above and below the recommended 150 minutes/ week.
T	Brisk walking, swimming, household chores, stationary biking, dancing, hiking, low impact aerobics.

Resistance Training

F	Limited available evidence, however, training for specific muscles groups should be performed on non-consecutive days of the week.
I	70% of 1RM, 10 reps performed to a point of moderate fatigue, but not failure. Beginners start with 1 set; experienced lifter can perform 2-3+ sets.
T	5-10 minutes warm up prior to resistance training. 1-2 exercises per major muscle group.
T	Free weights, machines, cables, bands, body weight.

*Independent of exercise experience in resistance training, all pregnant women must emphasize safety and adapt their exercise routine to the stage of pregnancy as some exercises may become more difficult as pregnancy progresses.

*The goal is to gradually achieve the recommended 150 minutes/ week though a combination of aerobic and resistance training.