Q: I’m a long distance runner and recently discovered I am pregnant (4-5 weeks). I have continued running but stopped training vigorously (I compete in marathons at a reasonably high level). I have been adhering to a recommendation of keeping my heart rate at 140-150 bpm, but I have found it difficult to move slowly enough to achieve this. My heart rate gets to 160 on hills, even though the effort is easy and I can chat — I used to train at 185-195 bpm on hard training days. How strictly should I follow these guidelines? And what about duration spent exercising at higher rates while pregnant?
A: Congratulations on your pregnancy. What I like best at athletes is that aerobic training is the best thing possible to get you in shape for the aerobic stress of labor and delivery. You know that you would never attempt to run a marathon without training, but it’s always amazing how manywomen don’t train for labor and delivery. There are no strict guidelines on how much you can run during pregnancy. Mary Decker Slaney has written that she did not feel well running after 20 weeks pregnancy, but resumed her strenuous workouts a month or so post partum.
Several issues need to be considered. First of all, central body temperature is important – high core temperatures for long periods of time can cause fetal malformations. So I usually caution the runners to stick to five or so miles at a time, as that is unlikely to raise their core temperatures, whereas 10 miles could pose a problem. I am also concerned about fetal growth – you want to make sure you take in adequate calories to cover your running and give the baby the extra 300 calories or so a day you will need to nourish that child. Your doctr should closely monitor fetal growth, and if the baby starts to lag behind, should ground them. Of course, any pregnancy problems could ground you, too. For example, if you developed a placenta covering the cervix that started to bleed, you have to go to bed rest.
Immediately post partum, you won’t be doing too much running, except for the baby’s needs. But there is no reason you can’t do vigorous walking. Your uterus is a very good guide – if you start bleeding heavily, you need to cut back, and get off your feet more. And what bothered me the most after delivery when I resumed running was breast discomfort, from heavy, lactating breasts. So get the best jog bra you can find, and hopefully, they won’t hold you down too long.
Have a good time, and listen to your body. Lots of tremendous physiologic changes are taking place for you in the next few months. And don’t feel wimpy if you are cutting back a bit.