Some media reports have cited guidelines for exercise during pregnancy and emphasized that it is important to exercise in moderation to avoid exhaustion, dehydration, and overheating. There are numerous guidelines available regarding exercise during pregnancy. The most cited guidelines are those by the American College of Obstetricians and Gynecologists (ACOG) in 2002 which state that in the absence of either medical or obstetric complications, 30 minutes or more of moderate exercise a day on most to all days of the week is recommended for pregnant women.
One problem with the ACOG guidelines is that they do not define moderate exercise. Some have interpreted them to mean that it is exercise that leaves one feeling energized and refreshed but not exhausted. However, this is subjective and the exercise intensity to achieve these feelings can vary greatly from person to person. This has led some to develop more recent guidelines in 2011, which state that increasing the amount of vigorous exercise and physical activity expenditure is an important goal for pregnant women, especially for those who are overweight or obese.
To do this, the researchers who proposed these guidelines (Zavorsky & Longo, 2011) suggested walking 3.2 kilometers per hour (1.98 miles per hour) for 6.4 hours a week or preferably exercising on a stationary bike for 2.7 hours a week. They stated that the best health outcome will come from vigorous exercise at greater than or equal to 60% of the heart rate reserve (HRR). HRR is the difference between the measured maximum heart rate and resting heart rate. The maximum heart rate is the highest heart rate one can achieve without severe problems during exercise. Some measurement devices of exercise intensity will measure the percent of HRR. If unable to access this information easily, the researchers suggested exercising at 70 to 75% of the maximum heart rate.
In short, the problem in Kim Kardashian’s case does not necessarily have anything to do with her exercising most days a week or 7 days a week because that is recommended in the guidelines. One simply needs to use common sense on not exercising in excess, particularly when there are extensive stressors present in one’s life such as divorce proceedings and a busy travel schedule. Higher stress levels increase levels of cortisol (a type of hormone) in the body, which can elevate other chemicals in the body that lead to miscarriage, premature contractions, and premature labor.
Lastly, there are numerous contra-indications to exercise during pregnancy such as lung disease, persistent bleeding, heart disease, and many others. Pregnant women should discuss their exercise regimen with their doctors before proceeding. This is particularly the case since large Danish study several years ago showed that exercise in early pregnancy is associated with an increased risk of miscarriage (Madsen et al., 2007). The authors of that study, however, suggested caution in interpreting the results however because limitations of the study design may have contributed to the association.
Suggested reading: Mayo Clinic Guide to a Healthy Pregnancy
Related blog entry: Anti-depressants in Pregnancy: What are the Risks?
The American College of Obstetricians and Gynecologists. Committee on Obstetric Practice. Exercise during pregnancy and the postpartum period. (2002). Int J Gynaecol Obstet. 99, 171–173.
Madsen M, Jørgensen T, Jensen M, Juhl M, Olsen J, Andersen P, Nybo Andersen A. (2007). Leisure time physical exercise during pregnancy and the risk of miscarriage: a study within the Danish National Birth Cohort. BJOG.114:1419–1426.
Nascimento SL, Surita FG, Cecatti JG. (2012). Physical exercise during pregnancy: a systematic review. Curr Opin Obstet Gynecol. 24(6):387-94.
Zavorsky GS, Longo LD. (2011). Exercise guidelines in pregnancy: new perspectives. Sports Med, 41:345–360.