When you're pregnant, your body goes through a number of changes, some that are so subtle you may not be aware of them. These changes are important to keep in mind as you develop and engage in your pregnancy exercise program:
- Shifts in your center of gravity: As your uterus pushes your abdomen up and out, your center of gravity may also change, and you may find that you can't balance as well as you used to, which can result in falling down. This is why, as your pregnancy progresses, many healthcare providers urge you to stay away from activities that require excellent balance.
- Joint instability: During pregnancy, your body releases a hormone called relaxin, causing your joints to loosen slightly and allowing the joint in front of the pelvis to widen so that your baby's head can pass through that region during birth. Be cautious with activities that require quick movements or a lot of balance.
- How much heat you generate: Throughout your pregnancy, you're like a little furnace, generating far more heat — and therefore raising your body temperature faster — than you did before you were pregnant. Both you and your baby can suffer if you overheat, so take extra care during these 40 weeks to stay away from situations that can raise your body temperature too high, like exercising outdoors in high heat or in a hot, unvented gym.
IntensityThe intensity of your workout is the effort you put forth as you exercise — hard, moderate, or easy. With some sports, you measure your intensity in miles per hour, revolutions per minute, per-lap time when swimming, and so on, so that you know empirically whether you're working harder or easier than the day before. In other sports, you can't measure intensity directly.
Regardless of what the speedometer is telling you, the important measure of intensity is how hard you think you're working out, based on how you feel (for example, saying, "Whew, that workout was hard" versus "Today's workout felt easy"). A specific tool, called the Borg Rating of Perceived Exertion (RPE) Scale, lets you assign a number to your response. The scale ranges from 6 (no effort at all) to 20 (maximum effort), with 13 being somewhat hard.You want to feel challenged and slightly winded while exercising, so keep your workouts in the 12 to 14 range or at a level that feels moderate to somewhat hard (you can talk while exercising without feeling exceedingly short of breath).
A rating of 12 on the RPE Scale won't always correlate with the same mile-per-hour rate throughout your pregnancy. One day, you may give a 12 rating when you're walking at a pace of 16 minutes per mile. On another day, later in your pregnancy or as a result of not sleeping well, you may give the same 12 rating when walking at a pace of 20 minutes per mile. Even though you're walking more slowly, you may feel that the two efforts are equally hard. And that's what's important — how the workout feels to you, not what the clock or speedometer says.
DurationDuration refers to the amount of time you spend exercising each day. When you're exercising at a 12 to 14 rating on the RPE Scale (see the preceding section) and you don't feel any discomfort or fatigue, you can begin to gradually increase the duration of each workout from 15 or 20 minutes up to 30 minutes or more.
Duration and intensity are super-glued together: You may be able to exercise without discomfort or fatigue for 45 minutes at a level of 12 on the RPE Scale but for only 30 minutes when you're exerting yourself at a level of 14. If, during a workout, you have trouble exercising for a longer duration, scale back your intensity from a 14 to a 12. If you still experience fatigue or discomfort at 12, reduce the duration by 5 or 10 minutes.
FrequencyFrequency refers to how often you work out — that is, how many days per week. Most experts agree that exercising for three to six days per week at a duration of 30 to 60 minutes per workout keeps you in good shape. How many days per week you can comfortably exercise depends on the following:
- How fit you are right now: The fitter you are, the more days per week you can work out without experiencing discomfort or fatigue.
- How your pregnancy is progressing: Is your baby growing normally? Are you gaining weight normally? Do you feel good? If you answer no to any of those three questions, cut back on the number of days you're working out each week.
- The intensity and duration of your workouts: If you're working out at a 14 on the RPE Scale for 45 to 60 minutes, you may find that three or four days per week is a more comfortable frequency than five or six days per week.
You need one day off per week while you're pregnant, even if you're convinced that you can work out seven days per week. You can, however, stretch your muscles seven days per week. And if one of your days is only a strength-training day, seven days is okay. But doing cardiovascular workouts all seven days will cause you to experience too much fatigue. Enjoy that day and the extra time you have as a result of not working out, and you'll be better prepared for the days that you do work out.
TypeThe type of exercise refers to what activity you choose as your workout. Ultimately, you want to choose activities that meet the following criteria:
- You enjoy the activity.
- The activity doesn't put your baby at risk.
- You can still do the activity as your center of gravity changes throughout your pregnancy.
- The activity makes sense as one to do during pregnancy. If you're doing an activity that you can't easily modify, or if your RPE Scale rating is more than 14 and modifying the duration and frequency doesn't lower the intensity, consider changing to a different type of activity.