Pregnant Mamas, Make Your Exercise Count!

January 12th, 2010

“Light Resistance Exercise During Pregnancy Does Not Affect Type of Delivery”.

This is the headline that came across my desk from Medscape  about a study published in the American Journal of Obstetrics & Gynecology. I have to admit my first reaction was shock, then outrage. For years we perinatal fitness instructors and other proponents of exercise have been trying to stress the importance of prenatal fitness to pregnant women. Our arguments stem from research done by obstetricians and researchers such as James Clapp, III, MD and Ann Cowlin, Dance and Movement Specialist. In their decades of research, they have found that regular, moderate intensity exercise, tends to shorten labor, increase the effectiveness of pushing, reduce the need for pain medications and interventions. The aforementioned study was in direct opposition from what I know and believe to be true anecdotally from my own perinatal fitness clients. But rather than just rant, I went and read the study to see how the researchers generated their data and how they reached their conclusions.

Study Design

In this particular study Spanish researchers took healthy yet sedentary pregnant women of low to medium moms2socioeconomic status in Madrid Spain and looked to see if having them do a limited amount of low intensity exercise impacted their deliveries. The women were all aged 25-35 years old with uncomplicated singleton pregnancies. The women in the study group began exercising at the beginning of the second trimester and continued for approximately 26 weeks. Their exercise regimen consisted of 8 minutes of warm up, approximately 20 minutes of toning and light resistance exercise and 8 minutes of cool down stretching performed 3 times a week. Exercise specialists monitored the exercise sessions to be sure that each lady’s heart rate remained at 80% of maximum output or less.  The researchers found that, in this study, there was no difference between rates of natural deliveries, instrumented deliveries or Cesarean deliveries even when potential confounding variables were controlled. While the researchers concluded that prenatal exercise is good for both mother and baby and did not complicate pregnancy, cause preterm labor or reduce the incidence of natural delivery, it did not alter the type of delivery a woman had.

Where They Went Wrong

Not intense enough exercise

After reading the study I completely understood why the Spanish researchers saw no impact of exercise on delivery. According to their journal article, they did not have the women engage in moderate intensity activity. Clapp, Cowlin and others have all found that pregnant women reap the most benefit from prenatal exercise when they engage in low impact moderate activity exercise.  Moderate intensity is defined as a rate of exertion in the range of 12-14 on a scale of 1-20 on Borg’s Rate of Perceived Exertion Scale. Exercising in the range of 12-14 enables a woman to be able to talk, but increases her cardiovascular effort contributing to endurance training.

Many exercise professionals, myself included, don’t use heart rate to monitor exercise intensity in pregnant women.  The physiologic changes of pregnancy inherently make a woman’s baseline heart rate go up. The American College of Obstetricians and Gynecologists used to recommend that pregnant women not increase their heart rates above 140 beats per minute (bpm), but for many pregnant women they reached 140 bpm just walking across the room! That is why the Borg’s Scale has replaced heart rate monitoring in many clinical exercise settings.

Not Enough Exercise

In this study, the women only exercised approximately 36 minutes per session and increased their heart rates for about 20 minutes per session. To develop any sort of strength or endurance conditioning, the American College of Sports Medicine recommends 20-30 minutes of exercise at targeted intensity 3-5 times per week. A combination of brisk walking, swimming or prenatal aerobics classes with strength training using free weights (usually not more than about 5 lbs) or exercise bands or tubing to accrue the 30-45 minutes of intense activity works well. I typically warm my clients up for 10-15 minutes before and cool them down for 10-15 minutes following the work out.

PregnantwomanonballTypes of Exercises

The study did not indicate what types of exercises were performed, but given they used light resistance bands, I am thinking some sort of strength training. Hopefully they included some sort of cardiovascular exercise such as brisk walking, swimming or aerobic movement. The strength training should have focused on maintaining muscle tone, muscle strength (especially upper body) and providing strength and support to the skeleton. Pregnancy creates forward movement of the neck and shoulders (a round shouldered upper body posture with a “stork neck”) while also creating lordosis (sway back) in the low back. CORE strengthening will help strengthen and stabilize the spine and skeleton and reduce the risk of pain or injury to the neck, shoulders, hips and back. Pelvic floor strengthening (Kegels and other exercises) should also be incorporated into the program to help prevent the development of urinary stress incontinence, tearing and or the need for an episiotomy during delivery and organ prolapse after delivery.

My Take

Prenatal exercise stills remains controversial in some obstetric circles, yet all the data to date support the idea that regular prenatal exercise is good for both mother and baby. Amongst birth professionals there still remains controversy as to what type and how much exercise is best. I have found that even with previously sedentary mamas-to-be, if they start exercising early in their second trimester and continue until they are ready to deliver (or as close as is comfortable), they are able to increase their cardiovascular endurance and muscle strength and tone just as if they would in the non-pregnant state. This conditioning enables the ladies that I train to have less pain and discomfort, to utilize less pain medication during labor and delivery, to spontaneously go into labor rather than needing to be induced, to have shorter labors (I’m seeing about 6-8 hours) and to more effectively push. These ladies don’t need “instrumentation” during delivery and I see a lower rate of cesarean sections.

One my call my results “anecdotal” and this is correct because my clients are not organized in to controlled study groups. But if my small prenatal fitness training population is any indication, women who engage in low impact moderate intensity exercise (in the range of 12-14 on Borg’s Rate of Perceived Exertion) for 20-30 minutes 3-5 times a week, will be more likely to experience less pain and discomfort during pregnancy, shorter labors, fewer complications during labor and delivery and a shorter recovery.

Mamas on Bedrest, Don’t despair! You too have an exercise option. Bedrest Fitness is a set of exercises designed specifically for pregnant women on prescribed bed rest. The exercises are simple but effective and easily done while in bed. Do part or all of the DVD, depending on your provider’s instructions.  Order your copy of Bedrest Fitness Here

I would love to hear the experiences of other birth professionals, perinatal fitness instructors and women who have exercised throughout their pregnancies. Please add your comments below and encourage other professionals and mamas to do the same!

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