Pregnancy brings with it physical changes galore. Some of them (a growing belly) are obvious. Others—a changing brain, an influx of hormones—are not. And even more of them? They’re exciting. For one, some research finds that both pregnant and postpartum women benefit from a slight increase in VO2 max, thanks to a significant rise in blood volume. That may make a difference when you exercise during pregnancy.
VO2 max is a measure of the maximum amount of oxygen that your body can utilize during exercise; it’s often used by endurance athletes as one measurement of overall fitness, explains Samantha DuFlo, P.T., D.P.T., a certified running coach and owner and founder of Indigo Physiotherapy in Baltimore. To fuel muscle contraction, your muscles basically use a unit of energy called ATP (adenosine triphosphate) through a process called aerobic respiration, and oxygen is transported through the body on blood cells.
In pregnancy, as that blood volume significantly increases, it gives your body more of an opportunity to transport oxygen, thereby facilitating VO2 max, DuFlo explains. This change even mimics the effects of blood doping, explains Stacy T. Sims, Ph.D., co-founder of CSO E.R.W., in which greater blood volume allows more oxygen to be carried to the muscles. “Coupled with cardiovascular adaptations to the increased demands of circulation to nourish the growing fetus, the overall physiological profile appears as if the woman can fly.”
Additionally? Estrogen, which is particularly important and present in high levels during pregnancy, can facilitate the development of muscle mass, she says. “More efficient muscle mass and development may also contribute to VO2 max.”
But here’s the thing: Most pregnant athletes don’t notice a remarkable difference in VO2 max (womp). And you can thank pregnancy’s other effects (read: nausea, fatigue, bigger boobs, or shortness of breath) for that.
But what research does show us is that the effects are likely there—and could last for weeks and even months postpartum. The benefits of exercise in pregnancy (even postpartum once you’re ready) are great. But before you exercise during pregnancy or postpartum, you want to be cleared by your healthcare provider, reminds Kecia Gaither, M.D., M.P.H., director of perinatal services at NYC Health + Hospitals/Lincoln.
Once you are? Here’s how to take advantage of small changes in VO2 max while not overdoing it with a baby on the way or as a new mom.
A higher VO2 max can boost distance-running performance and speed, but if you go into a pregnancy or the postpartum timeframe with too-high expectations, you’re setting yourself up for challenges, physically and mentally, with both running and motherhood, says Melissa Majumdar, R.D., a dietitian, runner, and mom based in Atlanta, GA. After all, you could wind up overdoing it, getting injured, or eventually even sidelining yourself. During pregnancy and new motherhood, there are things (like sleep deprivation or physical discomfort) that play into how much and how hard you’re able to work.
A better approach? “See any opportunity to train or to run as a blessing and an opportunity to have much needed time to yourself,” suggests Majumdar. Going into a workout with this kind of approach can help you not only take things one step at a time (key!) but also tune into your body, listen to it, and get the most out of every workout (which might be something different every time).
“During pregnancy, your body will tell you what you can tolerate,” adds Sims. “Do not think of this time as a progressive improvement, but as maintenance of fitness; the boost of cardiopulmonary adaptations are there to improve blood flow to the fetus and to keep the mom healthy.”
Also worth noting: If you’re pregnant, you have a whole new center of gravity due to your expanded tummy and spinal curvature, notes Dr. Gaither. Moving around throughout the nine months of pregnancy, your body might get used to this or it might find ways to compensate for the changes. Postpartum, your body slowly starts to return to its pre-pregnancy state and with that, everything from your gait and your center of gravity to the hormones running through your body change. Going slow and allowing yourself to adjust to your new body no matter what stage you’re at is important.
Change How You Move
Movement during pregnancy is hugely beneficial (because it helps regulate estrogen levels and process excess hormones, exercise can even help quell issues such as nausea during pregnancy, says DuFlo). Once you’re cleared to exercise postpartum, moving in the right ways can help you heal from birth and feel stronger in the process (not to mention the mental high). But if you find yourself unable to get back to or continue high-impact exercise such as running, know that there are other ways to take advantage of a higher VO2 max—namely through non-impact sports such as spinning or swimming, says DuFlo.
Postpartum, hold off on high-intensity and high weight-bearing loads until your pelvic floor muscles are strong again (a minimum of six weeks time), suggests Sims.
Fuel Yourself Appropriately
The demands of pregnancy and new motherhood are great—and they call for extra nutrition. If you’re pregnant with one baby think in terms of about 300 extra calories per day in the second and third trimesters. (If you’re pregnant with twins, think in terms of about 600 extra calories a day.)
Postpartum, if you’re breastfeeding, you need to make sure you’re eating enough to support yourself, your baby, and your workouts (if you are indeed back to working out). Try to eat about 500 calories more a day if you’re breastfeeding, suggests Majumdar—and know that this number rises if you’re back to working out. If you’re not fueling yourself appropriately, you won’t be able to get the most out of your days or your workouts, she notes.
Start to notice drops in your energy levels or differences in breast milk production? Those can be signs you’re not taking in enough food, she notes.
On top of focusing on easy, nutrient-dense foods—energy bars, avocado, nut butter, the likes—as a rule of thumb, make sure you’re feeding yourself when you’re feeding your baby, suggests Majumdar.
And remember: Fueling yourself with sleep matters, too. “Finding your individual groove with sleep, recovery, and fueling will allow a woman to hold onto her performance-boosting pregnancy adaptations,” says Sims.
Consult with a Pelvic Floor Physical Therapist
A physical therapist who focuses on the pelvic floor muscles can be hugely beneficial in both pregnancy and postpartum. “Hormones during pregnancy as well as the physical trauma of birth—even if uneventful—can cause pelvic floor weakness, core weakness, and other pelvic floor dysfunction,” explains DuFlo. “Running is an impact sport, so the muscles of the pelvic floor need to be able to sustain the impact of landing and the pressure created in the abdomen to prevent pelvic floor injury.” Pelvic floor physical therapy is also often included in general postpartum care in other countries. Working with one (you can find one here) can help you rehab, preventatively strengthen muscles, and prevent injury.