The plank exercise is a static hold that builds core stability by engaging multiple muscle groups simultaneously. For a pregnant person, maintaining core strength supports the spine against the shifting center of gravity and prepares the body for labor. However, the safety of performing the plank changes as pregnancy progresses and the abdominal wall stretches to accommodate the growing fetus.
Core Safety Guidelines by Trimester
During the first trimester, a person can typically continue performing the traditional plank without modification, provided they were doing it prior to pregnancy. The uterus remains low in the pelvis during these initial weeks, minimizing mechanical pressure on the abdominal wall. This allows for continued conditioning of the core muscles while the body undergoes hormonal adjustments.
The beginning of the second trimester, around 14 to 20 weeks, is when the uterus moves up and out of the pelvis, causing the abdomen to protrude. At this stage, the mechanical forces and increased intra-abdominal pressure (IAP) from a traditional plank become a concern. The growing weight places a downward strain on the abdominal wall and pelvic floor, necessitating a change in exercise approach.
By the late second and third trimesters, the full, downward-facing plank is generally discouraged due to the risk of excessive IAP. The body’s center of gravity shifts substantially, making the prone position awkward and difficult to maintain with proper form. Exercises that place direct strain on the midline should be swapped for alternatives performed in a standing, seated, or all-fours position.
Understanding Diastasis Recti
Diastasis recti (DR) is the separation of the two halves of the rectus abdominis muscle along the connective tissue known as the linea alba. This widening occurs naturally in most pregnancies as the uterus expands and hormonal changes soften the connective tissue. Traditional planking in later pregnancy can exacerbate this separation by placing excessive strain on the already thinned linea alba.
Exercises that cause a visible ridge, bulge, or doming along the midline of the abdomen indicate too much pressure for the core to manage. Doming is a clear sign that the integrity of the abdominal wall is compromised and the strain is increasing the separation. Continuing planks or similar exercises when bulging occurs can hinder the abdominal muscles’ ability to regain function postpartum.
To check for DR, a person should lie on their back with knees bent and feet flat on the floor. Place two or three fingers horizontally across the midline of the abdomen at the belly button. Gently lifting the head and shoulders slightly off the floor, as in a mini-crunch, causes the rectus abdominis muscles to contract. If a gap of more than two finger-widths can be felt between the muscle edges, it suggests diastasis recti. Assessing the depth of the separation—how far the fingers sink in—is also important, as a shallow gap is considered less concerning than a deep one.
Safe Modifications for the Plank Exercise
When the traditional plank becomes inappropriate, modifications allow for continued core engagement without straining the linea alba. The wall plank is the most regressed option. Stand facing a wall and place hands shoulder-width apart on the surface, keeping the body in a straight line at an incline. Moving the feet farther away from the wall increases the angle, making the exercise more challenging.
The incline plank offers a greater challenge while still reducing gravitational pressure compared to the floor. This variation involves placing the hands on a sturdy elevated surface, such as a bench or sofa arm, with the body angled down. The higher the surface, the easier the exercise becomes, allowing for progressive intensity as core strength improves.
The knee plank is another common modification for those with adequate strength, though monitoring for doming remains necessary. Assume a standard plank position but rest weight on the knees instead of the feet, maintaining a straight line from head to knees. Focus should be placed on engaging the deep core muscles, maintaining a neutral spine, and immediately stopping if any coning or discomfort is noted.
Core Exercises to Replace Planking
Once the abdomen is significantly larger or if signs of abdominal bulging appear, replacing planking with exercises that target the deep core muscles is recommended. The Bird-Dog exercise is performed on the hands and knees, alternating the extension of one arm and the opposite leg while keeping the torso stable. This movement effectively trains the core and back muscles without placing direct, downward pressure on the abdomen.
The side plank is an effective substitute that engages the oblique muscles and the deep core stabilizers while eliminating direct strain on the linea alba. It can be performed with the knees stacked and bent for a modified version, or with the legs straight for increased difficulty. This exercise is often tolerated later into pregnancy than the front plank.
Pelvic tilts and transverse abdominis (TA) engagement exercises are important for maintaining deep core function. Pelvic tilts involve gently rocking the pelvis back and forth while on hands and knees or standing, which strengthens the TA. TA engagement, sometimes cued as “hugging the baby” or drawing the belly button toward the spine, can be practiced in any position and helps provide internal support for the growing uterus.