Measuring Success: How Much Exercise is Needed During Pregnancy?

EAST LANSING, Mich. — As the medical community uncovers more evidence of the benefits of exercise during pregnancy, a Michigan State University researcher is looking to pinpoint the most reliable and valid ways to assess physical activity in pregnant women.

Determining the accuracy of several popular physical activity measurement tools during pregnancy and postpartum will significantly help researchers studying the health benefits of exercise during those time periods, said Jim Pivarnik of the Department of Kinesiology, who is leading the study.

Jim Pivarnik, professor of kinesiology and epidemiology. Image credit: Michigan State University.

“The health care community has undergone a dramatic change when it comes to pregnancy and exercise,” said Pivarnik, who has been studying the topic for more than two decades. “As more research shows physical activity helps decrease the number of pregnancy-related maladies as well as future chronic disease risk, we need to make sure we use the best measurement tools available.”

While newer research points to the benefits of exercise during pregnancy, the type, intensity and amount of physical activity that is most beneficial is unknown, Pivarnik said. Part of that uncertainty is that physical activity measurement tools used during pregnancy have been imprecise.

“The physiological and anatomical changes associated with pregnancy affect a woman’s overall physical activity behavior, as well as the energy she expends performing specific tasks,” he said. “Therefore, findings regarding physical activity measurements obtained from studies using nonpregnant women may not be applicable to pregnant and postpartum women.”

Helen Knull, newly appointed coach of MSU’s field hockey team, is pregnant with her second child and taking part in the study. She said volunteering for the study was a “no-brainer” for her.

MSU field hockey coach Helen Knull participates recently in a study measuring exercise during pregnancy. Kinesiology graduate student Rebecca Rudey takes measurements. Image credit: G.L. Kohuth.

“I was active throughout my first pregnancy, and it not only helped me feel better physically but from a mental standpoint as well,” she said. “It’s important when women are pregnant that you continue to do some sort of exercise, even if it’s only walking.”

As part of the study, Pivarnik and his team will examine results at three time periods to determine the reliability and validity of several measures: 20 and 32 weeks of pregnancy, and 12 weeks postpartum. During each visit, physical activity will be assessed by three different measures: accelerometry (two ActiGraph accelerometers and one SenseWear Armband accelerometer), an Omron pedometer and the Pregnancy Physical Activity Questionnaire.

In addition, study participants will visit the Department of Kinesiology’s Human Energy Research Laboratory to complete a specific set of physical activities on two occasions, one week apart.

Reliability of the measures will be graded by comparing the energy expended during the first week with the second week in the women’s home environments, and comparing the energy expended during the first laboratory visit with the second laboratory visit.

*Source: Michigan State University.

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