The question of maintaining or building muscle during pregnancy is common, especially for those with an established fitness routine. While the body’s priority shifts to supporting a developing fetus, strength maintenance is generally a safe and encouraged goal for most individuals. Modest muscle gain, or hypertrophy, is technically possible, though the degree depends heavily on pre-pregnancy fitness level and the stage of gestation. The focus of any training program during this period must shift away from maximal performance toward functional strength and safety, informed by the body’s profound physiological changes.
Physiological Hurdles to Hypertrophy
The internal environment of pregnancy presents unique challenges that make achieving significant muscle hypertrophy difficult. A major hurdle is the effect of the hormone relaxin, which increases early in the first trimester. Relaxin works to loosen ligaments and connective tissues throughout the body, most notably in the pelvis, in preparation for childbirth. This increased joint laxity means joints are less stable, necessitating a shift away from heavy, maximal lifts toward lighter loads and movements that emphasize stability. The risk of injury is heightened when attempting to produce high levels of force, as the connective tissue attaching muscle to bone is more elastic than usual.
The body also undergoes a profound metabolic shift where energy is primarily channeled toward fetal growth and maternal support tissues. This physiological reprogramming means that sustaining the energy surplus required for maternal muscle building is challenging. Mechanical load, which is one of the primary drivers of muscle growth, must often be reduced due to joint instability. The ultimate goal of strength training during pregnancy therefore shifts from maximizing muscle mass to maintaining current functional strength.
Mandatory Safety Adjustments for Strength Training
Maintaining a consistent strength routine during pregnancy requires specific modifications to ensure the safety of both the parent and the fetus. A primary concern is the supine position, which should be avoided after the first trimester (approximately 20 weeks). As the uterus grows, lying flat can compress the inferior vena cava, a major vein that returns blood to the heart. This compression can lead to Supine Hypotensive Syndrome, resulting in symptoms like dizziness, low blood pressure, or nausea, and potentially reducing blood flow to the placenta. To safely perform exercises that involve the back, such as chest presses, the torso should be propped up using an incline bench or wedges.
Another important modification involves managing intra-abdominal pressure by avoiding the Valsalva maneuver (holding one’s breath during exertion). Bearing down while lifting can place excessive pressure on the pelvic floor and abdominal wall. Instead, exhalation should be coordinated with the effort portion of the lift, such as breathing out while standing up from a squat.
Exercise intensity should be monitored using the Rate of Perceived Exertion (RPE) scale, aiming for a moderate level, typically no higher than a 6 to 7 out of 10. This RPE scale is the preferred method over outdated heart rate maximum guidelines, as it accounts for the individual’s daily variations in energy and fatigue.
Any exercise session should stop immediately if warning signs appear:
- Vaginal bleeding
- Fluid leakage
- Persistent pain
- Sudden dizziness
- Shortness of breath
Consulting a physician before starting or continuing any exercise routine during pregnancy is the first and most important step.
Fueling Muscle Maintenance and Growth
Supporting muscle tissue development and maintenance during pregnancy relies heavily on specific nutritional intake. Protein is the building block for all tissues, and the requirement increases significantly to support maternal muscle repair and fetal development. Most pregnant individuals should aim for a minimum of 60 grams of protein daily, with some recommendations suggesting up to 100 grams, depending on pre-pregnancy weight and physical activity level. This protein is used to create the baby’s cells, hormones, and organs, as well as to increase maternal blood volume. Consuming nutrient-dense sources like lean meats, dairy, eggs, and legumes ensures a complete profile of essential amino acids.
Adequate caloric intake is necessary to prevent the body from breaking down muscle tissue for energy. Starting in the second trimester, the body requires an additional caloric surplus, often around 300 calories per day, to meet the demands of fetal growth and increased metabolism. Timing the intake of protein and carbohydrates around workouts can help optimize muscle recovery and energy levels. Proper hydration is a continuous requirement, as increased blood volume and metabolic processes raise the body’s demand for water, which is particularly important during exercise.