Even when you're at rest, your heart is working hard to pump blood through your body. During pregnancy your extra weight and your baby's oxygen needs make your heart work even harder. Exercise demands even more of your heart because your muscles need plenty of oxygen when they are at work.
As you progress through your 3rd trimester, you'll be asking your heart to work continuously harder. That's all right-your heart can take it, as long as you don't have heart disease. There's no need to curtail your exercise if your heart rate increases; it's normal that if you work hard, your pulse will go up.
"Vigorous" exercise means different things for different people. Vigorous exercise for a sedentary woman may be only a warm-up for a marathoner. What's important is that you avoid pushing yourself too hard; "too hard" means to your own point of discomfort. It's OK if you notice your breathing speeding up as you exercise, but you shouldn't be pushing so hard that you can't talk. Listen to your body. Any kind of movement is good, even if it's slower and less intense than your prepregnancy and early-pregnancy activity.
Originally published in You & Your Baby: Pregnancy.
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