Prenatal yoga is intended to ease the discomforts of pregnancy and increase strength and stamina. It's not a good idea to start anything new or strenuous during pregnancy if you are not already conditioned for heavy exercise. Yet for already physically active women it is generally acceptable to continue a moderate routine if there are no contraindications to exercise during pregnancy. Heat dissipation is a concern however. Hot, humid environments present a significant risk to any exerciser, and the risk is heightened during pregnancy. Even for experienced hot yoga practitioners, the typical hot yoga environment requires careful consideration of the safety of the mother and child.
Regular as opposed to intermittent exercise is recommended during pregnancy for both mental and physical benefits you'll receive. The appropriate type and mode of exercise is dependent on your physical activity prior to exercise, your fitness level, and avoiding situations that put you, the fetus, or both at risk. Risks during the first, second and third trimesters vary. As you consider doing hot yoga practice during pregnancy, three concerns emerge; heat dissipation, dehydration, and biomechanical issues. Heat dissipation and dehydration are primary considerations during the first trimester. Biomechanical issues manifest in later months of pregnancy.
Hot yoga typically is done in room temperatures of 90 to 105 degrees and at 60 to 70 percent humidity. That equates to a heat index -- or temperatures that feel like -- they range from 100 degrees to 149 degrees. Thermoregulation, or cooling the body, is challenging in hot environments even for elite athletes. Sports events are often canceled or postponed when temperatures reach 83 degrees in some climates. If there is no convection provided through a breeze or fans, high humidity prevents evaporation. If the air temperature is higher than your body temperature, your body temperature will continue to rise.
Finally, specific yoga poses inherent in a vigorous practice such as hot yoga that require lying on the belly or extreme balance challenges warrant avoidance or modifications.
The body regulates heat through sweating. Sweating to regulate body temperature can present a secondary problem for pregnant exercisers. In addition to elevating your core temperature, fluid losses could pose a threat. Evaporation of sweat is required for it to cool the body. In hot humid environments that is not possible. If the sweat is wiped away with a towel, as would be a natural response, the body temperature will continue to rise and the additional sweat that is produced will promote greater fluid losses. Fluid losses of as little as 2 percent of your body mass will impair your ability to exercise. More importantly to you as an exercising mother, fluid losses increase your heart rate and decrease blood volume, potentially causing fetal stress.
Joint laxity caused by the hormones can cause instability and change your body's ability to withstand forces it normally tolerates. The hot yoga environment enhances flexibility and potential risk is greater in the pregnant woman who pushes beyond her usual flexibility limits. The hormone increases progressively during the pregnancy making joints more vulnerable in later stages of pregnancy.
Anyone who exercises in the heat needs to acclimatize to it gradually. Brief periods of exposure and low intensity levels allow a body to get used to heat stress. Hot yoga participation should be postponed until after the third month of pregnancy, however, because of the risk of overheating during that period. Increasing cool fluid intake can help you avoid overheating and dehydration if environmental conditions are not too severe. You do have an enhanced ability to dissipate heat as your pregnancy progresses. This is due to both increased blood flow to the skin and to increase tidal volume, which allows you to lose heat through exhalation. Knowing and remaining within your flexibility limits will reduce problems from joint laxity.
Exercise during pregnancy helps to decrease backaches, constipation, bloating, and swelling and helps to improve or maintain your endurance, stamina, and energy. It will improve your mood and enhance your sleep. The successful outcome of pregnancy is based on your health and on the health of your baby. Eliminate or reduce potential risks to you and your fetus now for a healthy pregnancy and baby. Discuss the appropriateness of any exercise with your doctor before you participate.
- “ACSM’s Guidelines for Exercise Testing and Prescription”; ACSM; 2006
- “ACE Advanced Health & Fitness Specialist Manual”; Cedric Bryant and Daniel Green; 2009
- “Exercise in Pregnancy”; Raul Artal Mittlemark, et al.; 1991
- "Physiology of Sport and Exercise"; Jack Wilmore, et al.; 2008