Pregnancy and Running

Contributed by Dr. Steven T. Devor – Director of Performance Physiology for MIT and OhioHealth, and Associate Professor of Exercise Physiology, Department of Human Sciences, and Department of Physiology and Cell Biology, The Ohio State University

For many decades the medical recommendation regarding exercise during pregnancy was that women should exercise very little, or perhaps not at all. As with many things though, research has informed and reshaped our thinking and now the American College of Obstetricians and Gynecologists routinely advises that expectant mothers who were previously active should continue on with their exercise programs. As I will discuss, caution is advised. However, as long as prudent precautions are observed and taken, continuing to run while pregnant for women that ran regularly before pregnancy is acceptable and even recommended.

Following a full release from your physician to proceed with your training, your weekly running mileage will be determined in large measure by how much you were doing before. For example, if you regularly ran five or more miles a day, you can keep logging those miles, albeit at a gradually slowing pace. However, if you ran at an eight-minute per mile pace before you were pregnant, you may discover that an 11-minute per mile pace during pregnancy, especially during the third trimester, is just as challenging. Your body will tell you when it is necessary to slow down. The important thing is to listen to your own body and the signals it is sending you. And do not push through pain or exhaustion. Again, now more than ever, listen to your body.

Maintaining your running program during pregnancy is not just about you as an expectant mother. Increasingly large amounts of research clearly indicate that aerobic exercise performed during pregnancy improves the health of the baby. And, not to be overlooked, maintenance of an aerobic exercise program helps to minimize back pain, lessens excessive and unhealthy weight gain, improves sleep quality for the expectant mother, and reduces delivery time and complications. Evidence of this comes from a recent published research study that reported women who maintained their running during pregnancy tended to have fewer pregnancy-associated physical discomforts, gained approximately 8 pounds less than those that stopped exercising, and they did not sustain more running related injuries. Additionally the authors reported that the women had easier, shorter, less complicated deliveries that required less medical intervention. Be mindful though, caution and a reduced per mile running pace are the essential elements.

There is without question a tremendous amount of information available on running during pregnancy, but very little of that information offers specifics on how exactly to continue your run training through pregnancy. One reason is due to the fact that there are many important variables that come into play during pregnancy that prevent women from following a traditional half or full marathon training plan. Trying to follow the same training plan you did before becoming pregnant may result in expectant mothers making poor decisions in order to get in a training run at any cost. If you have your medical release, proceed. But proceed with caution and with the knowledge that your training and performance goals will likely be different.

In a number of ways you have now have two finish lines ahead of you as an expectant mother; the race you are training for, and the birth of your baby. And at times, those two finish lines may conflict with one another and cause you and your baby unneeded stress. My advice is to always let the healthy birth of your baby drive your run training decisions. Train with the mentality that embraces where you currently are in life. You are an expectant mother who wishes to maintain her running and potentially complete a race. Resist the temptation to train for the long-term goal of where you eventually want to be once you have delivered your baby. That time will come. Training and performance goals must be necessarily adjusted during pregnancy.

As you progress from month to month during your pregnancy, your running speed per mile will certainly need to slow, and even at these slower paces your training will become more challenging. Simply put, to run at the same pre-pregnancy pace per mile your heart now has to increase the number of beats per minute to deliver oxygen to not only your working skeletal muscles, but also to your developing baby. This fact alone will necessitate a slower pace per mile when you are training. Many women report that it can be frustrating to run at a slower pace than they are accustomed to, but it is not uncommon for your fitness to be maintained as the physical effort that is required to run during pregnancy is increased.

A certain percentage of women continue to run very hard with high intensity while pregnant. In my opinion as an exercise physiologist, pregnancy is not the time to push your body to high levels of physical exertion. Your body is working hard to create life. Focus on the fact that you are able to maintain your fitness, and celebrate the fact that you are moving and being healthy. Your training plan needs to be flexible, consistent, and done at a level that is safe for both of you. Pushing your body to achieve hard running efforts increases the likelihood for injuries, especially in your hips, knees, and ankles, as certain hormones are now being released that cause your joints to be more lax. The increased joint laxity will ultimately help your pelvis relax for the birth of your child.

My advice is to not focus as much on heart rate training during pregnancy. Instead focus increasingly on your perceived exertion while running. That is to say accomplish your run based more upon on how it feels instead of a number of heart beats per minute or a heart rate zone from your monitor. Reconsider your goals and direct your efforts increasingly toward running regularly and consistently, as opposed to being linear like a typical half or full marathon training plan. This new training plan may be set up to embrace running 5 to 6 days per week for 40 to 90 minutes, without so much concern for actual mileage. All of these runs should be accomplished at an easy to moderate effort. Focus on your breathing, being able to breathe comfortably, without struggling for air. Overexertion, or training at to high of a heart rate, may lead to a dangerous reduction in blood flow to the baby.

Additionally, and importantly, your running stride and gait pattern will have to change when pregnant. Your altered stride pattern is due to a shifting center of gravity, and this becomes more pronounced as you move from the first trimester to the third trimester. Be aware of your altered stride pattern, and be especially careful when on less than solid ground. Given the shifted center of gravity your pregnant body now has to adjust to, training outside in the winter when pregnant can be particularly hazardous.

The treadmill provides a predictable and safe terrain and still permits you to achieve a quality workout. Nearly all experienced runners can become overly concerned with comparing the quality of training inside versus outside. Remember, at this time your training plan and running needs to be focused on consistency and achieving a solid workout, not necessarily on a certain pace or in certain environmental conditions. By permitting yourself to have adjusted and flexible goals each day and overall, you will not be setting yourself up for a potential disappointment. Stay focused on completing your goal race and maintaining your fitness. Celebrate the fact that you are doing something very healthy for both you and your unborn baby. By continuing to run during your pregnancy you are creating many health benefits for both of you.

As an exercise physiologist, let me summarize with the following general guidelines to assist in maintaining a safe and healthy environment for you and your baby while running and exercising during pregnancy:

  • Any woman that desires to run or exercise during pregnancy should first get her physician to release her to do so. Certain medical conditions, such as preterm rupture of membranes, pregnancy-induced hypertension, preterm labor, persistent second- or third-trimester bleeding, poor fetal growth, incompetent cervix, or multiple-birth pregnancy, will likely require modifying or avoiding exercise.
  • Hydration is absolutely critical when exercising during pregnancy. Drink plenty of water before, during, and after exercising, particularly in very hot or humid weather or when using a treadmill inside. An increase in core body temperatures due to dehydration in early pregnancy can cause fetal defects, and dehydration in late pregnancy is associated with premature labor.
  • Before every single run always make the time to include a gentle warm-up before your training really commences. Getting yourself going slowly will result in a much better training session overall.
  • Dress in comfortable clothes that wick sweat and keep you cool. Be certain your shoes are not worn down and that they have adequate cushioning and support for your feet and Achilles tendon. A very well fitted sports bra is essential during pregnancy.
  • Stop running or exercising immediately if you experience symptoms such as chest pains, vaginal bleeding or uterine contractions, or if your membranes rupture.
  • Eating a whole food, nutrient dense, largely plant-based diet that includes healthy fats is more important than ever when pregnant. Between your running and pregnancy, your daily caloric intake will need to increase.
  • Avoid exercises where you are placed on your back after the first trimester or whenever you feel dizzy, lightheaded or nauseated. The increased weight of your uterus applies additional pressure on the vein that is responsible for returning blood from your lower body back to the heart.


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