Staying Fit While Pregnant – Adapting to This New Body

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Over the years of working in the fitness industry I have developed a great appreciation for the human body, and how it is able to adapt, strengthen, and repair itself unknowingly to its user. Now that I am pregnant, my admiration for the human body (specifically the female body) has grown even further, because of the dramatic transformation the body undergoes to accommodate a growing baby.

I am 22 weeks along (over halfway in this 40 week journey) and my body continues to change and adapt to its new role as home to our little nugget. There are the obvious physical changes that can be seen (ie my growing belly), but the physiological changes that are affecting my fitness level are what fascinate me most.

Much of my week involves working out, either on my own, or leading a HIIT or spin class, so early into my pregnancy one of the more noticeable changes was my plummeting cardiovascular endurance level. There are a number of factors that come in to play in this shift. One interesting reason for my loss in cardio stamina is that within the first couple weeks of being pregnant my hormones had already signaled my body to relax the blood vessels to make room for the increased amount of blood (about double the volume) my body will be producing. Much of this additional blood will help support the hard working uterus and placenta.¹ But this blood volume increase happens gradually over the nine months. As a result, for much of my pregnancy my heart has had to work extra hard and beat faster to pump my blood through these dilated blood vessels. At rest my heartbeat is 18-20% faster than pre-pregnancy!¹ So you can image the struggle my cardiovascular system has endured when exercising. It literally has been an exhausting process to circulate my oxygenated blood to my muscles then back to the heart! Now that my pregnancy has progressed my blood volume has risen to better match the dilated vessels. However, my cardiac output (the volume of blood pumped by the heart per minute) will continue to increase until the 8th month to “ensure adequate blood supply to all body tissues.”²

Exercising throughout this pregnancy has been a major factor in sustaining a higher level of cardio endurance. Because of exercise my “plasma volume, red cell volume, and total blood volume … are at least 10-15% higher” compared to women who do not exercise during pregnancy.¹ This extra blood helps fill those dilated blood vessels and deliver more oxygen to muscles. In addition, working out while pregnant has also enhanced my “respiratory system by improving oxygen transport and uptake,”¹ making my body even more efficient compared to my non-exercising pregnant counterparts.

Although my cardio has been suffering, I am grateful to still feel strong. I find it amusing that some people treat me as if my strength miraculously disappeared when I became pregnant, and I can no longer lift even a 10 lbs dumbbell! Well I can still lift weights, and thankfully I am encouraged to keep up with strength training during pregnancy. However, my “joints have become less stable under the influence of the hormone relaxin,”² therefore I can only maintain my strength with no major increases to my weightload. Instead I now focus on low weight, high repetition lifting to achieve muscle fatigue.¹ It will be important to continue my strength training as my belly grows and I become even heavier. The added pressure on my joints and back will likely cause me discomfort, so a strong body will be key to maintaining good posture and minimizing pain.

Weight gain is the most obvious affect during pregnancy. Again this is something the body does naturally to support the life of a new baby. At first gain weight was a hard idea for me to handle, I was proud of my strong body and worried of the changes in my appearance. The first 4 months were tough because I did not look pregnant, I just looked and felt “thicker.” Now that I am almost 5 months I have embraced my new shape and wear my new maternity jeans with pride!

Something else has changed in me that I did not expect. A new maternal mentally has kicked in, where it is no longer just about me, but about the health of our baby. That means embracing the changes to my life and my body (including my fitness level and weight gain), and appreciate the absolutely amazing process that is happening inside of me!

I love to exercise, and it is wonderful I can continue to stay strong and active throughout my pregnancy. Stay tuned for next week’s blog where I will discuss the many benefits of exercising while pregnant.

I am also excited to announce that I will be leading an 8 week Prenatal Fitness Class at 10am on Sundays starting February 21! Please email me for more information and to register! All fitness levels welcome!


1. Gwen Hyatt, MS and Catherine Cram, MS (2003) Prenatal & Postpartum Exercise Design
2. Peggie Williamson, MS, CHES, CPT, CFT (2011) Exercise for Special Populations

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