WHOOP Pregnancy Study Finds HRV and RHR by Trimester

A West Virginia University study tracked HRV and RHR trends across trimesters using WHOOP.

While recent studies encourage women to continue exercising during pregnancy, there is still a lack of continuous physiological research in the field. A recent study led by West Virginia University School of Medicine sought to change that by monitoring pregnant women with WHOOP. This piece covers safe exercise guidelines and explains how your cardiovascular metrics naturally shift across trimesters.

Ideal exercises during pregnancy

Yes, it is safe and highly beneficial to exercise during pregnancy if you are already active and have clearance from your physician. Staying active supports your cardiovascular health, helps manage physical stress, and prepares your body for delivery. Focus on low-impact activities that maintain your fitness without placing undue stress on your joints or pelvic floor.

• Swimming: Provides full-body cardiovascular training while the water supports your joints and changing center of gravity.
• Stationary cycling: Offers a safe, low-impact way to sustain your cardiovascular baseline without the fall risk of outdoor cycling.
• Strength training: Helps maintain muscle mass and supports your changing posture, provided you prioritize proper form and reduce weight as your pregnancy progresses.

Exercises to avoid during pregnancy

As your body changes, certain movements introduce unnecessary risk. Listen to your body, avoid pushing yourself to maximum exertion, and stop immediately if an exercise causes pain or dizziness. You should generally avoid the following activities:

• Contact sports and fall risks: Activities like outdoor cycling or skiing increase the risk of abdominal trauma or dangerous falls.
• Supine exercises: After your first trimester, avoid exercises that require you to lie flat on your back, as this position can restrict blood flow.
• Extreme heat: Skip hot yoga or exercising in high temperatures, which can elevate your core temperature to unsafe levels.

Pregnancy doesn't have to mean loss of fitness

The study tracked active women to isolate pregnancy as the primary variable, monitoring their HRV and RHR trends through each trimester and postpartum. "By enrolling women who exercise, we made the variable pregnancy as opposed to enrolling pregnant women and then adding exercise," said Dr. Rowan. Preliminary results from all 12 women showed a telling narrative of health and fitness.

During pregnancy, cardiac output increases to pump more blood to the heart. This causes an increase in RHR and a simultaneous decrease in HRV due to shifts in autonomic control. While these physiological changes can make exercise feel more challenging, it does not mean your routine is physically detrimental.

"Many female athletes are concerned about the progress or lack thereof of their fitness journey during pregnancy," said Jenna Wallace, WVU pediatric psychologist and member of the research team. "The data we are gathering can help obstetricians to encourage and guide their pregnant patients and also to provide peace of mind to female athletes who prioritize the well-being of their babies during this important stage of life."

These physiological indicators of health and fitness show how pregnancy and delivery can improve overall health.

Helping pregnant women stay healthy through continuous monitoring

By using a non-invasive tool like WHOOP to monitor heart rate, HRV, Sleep, Recovery, and Strain, researchers can learn an incredible amount about maternal health. These insights reinforce that a healthy pregnancy is not one-size-fits-all, especially regarding exercise. Every woman's body is different, and continuous monitoring helps navigate conflicting medical advice.

Members can track these physiological shifts directly in the WHOOP app using Pregnancy Insights. By logging your pregnancy due date in the Journal, WHOOP provides personalized weekly updates on how your resting heart rate and HRV are trending compared to other pregnant members. This feature offers peace of mind and helps you adjust your daily Strain based on your body's changing needs.

WHOOP is honored to be the wearable device chosen for this study and remains committed to advancing research in women's performance. For more information, you can read the full article from WVA here or read the full paper on the study.

Frequently asked questions about exercise during pregnancy

When should you stop exercising during pregnancy?

Stop exercising and consult your doctor if you experience dizziness, chest pain, fluid leaking, or severe shortness of breath before exertion. Your body signals when it needs rest, and paying attention to your daily metrics can help you understand when to scale back your strain.

How does heart rate change during early pregnancy?

During early pregnancy, your blood volume increases to support the fetus, causing your resting heart rate to rise and your HRV to decrease. These normal physiological shifts explain why your usual workouts may feel more challenging during your first trimester.

Can you start a new exercise routine while pregnant?

If you were inactive before pregnancy, you can still begin a safe, low-impact exercise routine like walking or swimming by starting slowly and gradually increasing your duration. Always consult your healthcare provider before starting any new fitness program.