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Exercising when pregnant can be a safe and healthy activity, but you need to be aware of the appropriate heart rate and exertion limits that apply. The main reason for limits is that a marked change in fetal heart rate or temperature during or after exercise can cause fetal distress and may result in a lower birthweight or a less healthy birth outcome. Issues such as a lack of oxygen or overheating of the fetus are of serious concern so care must be taken not to over-exert yourself when exercising.
Studies have shown that fetal heart rate remains normal as long as the maternal heart rate stayed at or below 140bpm, which is a moderate exercise intensity level. When exercise intensity increased to 180bpm fetal heart decreased significantly in 20% of the participants, and this should be avoided.
Heart rate is the most effective way to monitor the intensity of your exercise. It is best measured with a heart rate monitor, but can be taken with a timer and your wrist or neck pulse.
The typical exercise range for a normal person is 65%-85% of their maximum heart rate. However, for pregnant exercisers ACOG guidelines recommend an upper limit of 140bpm, or approximately 70% of maximum. This limit is best measured with a heart rate monitor and investing in a monitor is a wise idea. Good heart rate monitors can be purchased from local sports stores, and reliable brands like the Polar A1 or A3
If you don't have a heart rate monitor then another good way to measure your exercise intensity is by using a scale called Perceived Rate of Exertion (PRE). PRE is a self-evaluated scale that runs from 5-10 and has certain physical signs associated with each level. The scale runs like this:
|
PRE Score |
Rating |
Physical Signs |
|
5 |
Light |
Light sweat on the brow, light breathing |
|
6 |
Easy |
Easy breathing, could chat away merrily! |
|
7 |
Moderate |
Puffing slightly but comfortable, can still hold a conversation |
|
8 |
Challenging |
Challenging work level, sweating, need to take pause between sentences |
|
9 |
Tough |
Hard breathing, difficult to talk, muscles burning |
|
10 |
Maximum! |
Full pace, gasping! |
To achieve a safe exertion level when exercising your PRE should not exceed 7 on the above scale. Interestingly, PRE underestimates heart rate in pregnant women, so if you do use this method be sure to be very cautious about your exertion levels when exercising. If in doubt take it slightly easier, or look to use a heart rate monitor!
Once you have finished your exercise be sure to take a good 5-10mins of gradually decreasing intensity exercise to cool down. A stretch is also a nice way to finish off the cool down period.
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