Restoring core strength after birth: a safe progression for the first months

Postnatal recovery · Updated July 2026 · All articles

Restoring core strength after birth is one of the most talked about but most misunderstood aspects of postnatal recovery. Social media is full of "bounce back" ab workouts that are, frankly, the wrong starting point. The postnatal core is a system that has been significantly changed by pregnancy, not just weakened. Getting it back takes a thoughtful progression, and that progression starts much earlier, and goes much slower, than most people expect.

Why the postnatal core is different from just "being weak"

During pregnancy, the abdominal muscles are progressively stretched outwards as the uterus grows. The linea alba, the strip of connective tissue that runs vertically down the centre of the abdomen and joins the two sides of the rectus abdominis (the "six pack" muscle), is placed under significant tension. In many people, this leads to diastasis recti: a widening of the gap between the two sides of the rectus, where the connective tissue at the midline has stretched and thinned.

Some degree of widening at the midline is normal in pregnancy, and a gap alone is not the whole story. What matters for function is whether the linea alba can generate tension when needed, that is, whether the connective tissue has enough integrity to transmit force effectively. A person with a measurable gap but good linea alba tension may have better core function than a person with no gap but poor tissue quality.

Additionally, the pelvic floor has been under sustained load during pregnancy and may have been stretched or strained during a vaginal birth. The pelvic floor and the deep abdominal muscles work together as part of the core pressure management system. If the pelvic floor is not functioning well, attempting to strengthen the superficial abdominal muscles in isolation can create problems rather than solve them.

The difference between core stability and "six pack" training

The core is not just the visible abdominal muscles on the front of the body. It is a cylindrical system made up of the diaphragm at the top, the pelvic floor at the bottom, the transverse abdominis wrapping around the sides, and the multifidus muscles at the back. This system works together to manage pressure within the abdominal cavity and provide a stable base for the limbs to work from.

Traditional "core exercises" such as sit-ups, crunches, and v-sits target the rectus abdominis, the most superficial layer. These exercises generate high intra-abdominal pressure and are not appropriate in the early postnatal period because that pressure is directed downwards into the pelvic floor and outwards through the midline, both of which are still healing. Starting here before the deeper system is working well is like trying to build the top floor of a house before the foundation is solid.

What not to do in the early weeks

For the first six to eight weeks after birth, avoid sit-ups, crunches, oblique twists, full planks, and any exercise that causes visible doming or coning at the midline of the abdomen (where the skin pushes outward in a ridge during the effort). Also avoid heavy lifting that involves straining and breath holding, high-impact exercises such as running or jumping, and anything that causes pelvic floor symptoms such as leaking, heaviness, or pressure in the perineal area. These are signs that the load is too great for the system at that stage.

After a caesarean section, additional caution is needed in the early weeks because the abdominal wall has been cut through layers that need healing time. No exercises that create tension across the wound or direct abdominal loading should be done until the wound is fully healed and you have been cleared by your care team.

Stage one: diaphragmatic breathing

The starting point for postnatal core rehabilitation is diaphragmatic breathing, also called belly breathing. This is not complicated, and it can be started as soon as you feel ready in the early days after birth, including after a caesarean once the initial pain levels allow it.

Lie on your back with your knees bent and your feet flat on the floor. Place one hand on your chest and one on your lower abdomen. As you breathe in through your nose, allow your lower abdomen to rise gently against your hand, your ribcage to expand, and your pelvic floor to gently descend and soften. As you breathe out through your mouth or nose, your abdomen falls, your ribcage narrows, and your pelvic floor gently lifts. Allow this to happen naturally rather than forcing it.

This breathing pattern reconnects you with the natural movement relationship between the diaphragm and the pelvic floor, which is the basis of good core function. It also gently activates the deep abdominal muscles without creating excessive pressure.

Stage two: transverse abdominis activation

Once diaphragmatic breathing feels natural, usually within the first one to two weeks, you can add a gentle activation of the transverse abdominis (TA), the deep corset-like muscle that wraps around the trunk. In the same lying position as above, as you breathe out, gently draw your lower abdomen inward and upward, as if you are lightly pulling your hip bones together or drawing your lower belly away from the waistband of your underwear. The contraction should be subtle, not a strong bracing or sucking in. Hold for a breath or two and then release fully on the next inhale.

This is not the same as pulling your stomach in tightly. The effort is moderate, perhaps 20 to 30 percent of your maximum contraction rather than gripping hard. Combine this with a coordinated pelvic floor lift and hold during the breath out, releasing fully on the inhale.

Stage three: adding limb loading

Once you can activate the deep core with consistent breathing coordination and without symptoms, you can begin to challenge the system by adding gentle limb movements while maintaining that activation. A common starting progression is heel slides (lying on your back, slowly sliding one heel along the floor while breathing and maintaining gentle TA activation) followed by leg lifts with knees bent, progressing to marching movements.

Throughout all of these, watch for signs of doming or coning at the midline, any feeling of pressure or heaviness in the pelvic floor, breath holding, or compensatory tension in the neck or shoulders. Any of these signs indicate the load is too great and you should return to the previous stage.

Side-lying exercises and seated exercises that engage the obliques and deep stabilisers without direct spinal flexion can be introduced at a similar time. They are generally better tolerated than supine exercises as the posture requires less from the pelvic floor.

How to check for diastasis yourself

You can do a simple self-check to see whether you have a significant diastasis recti. Lie on your back with your knees bent. Place your fingertips horizontally across the midline of your abdomen, just above your navel. Slowly lift your head off the floor, as though beginning a crunch, without pulling on your neck. Feel along the midline for a gap between the two ridges of muscle on either side. Note how wide the gap is (in finger widths) and how deep your fingers sink before meeting firm tissue.

A gap of two finger widths or less with firm tissue underneath is generally considered within normal range. A wider gap, or one where your fingers sink deeply without meeting resistance, suggests the linea alba tension is reduced. However, a home self-check is imprecise, and if you have concerns a physiotherapist can give a much more accurate assessment using palpation or ultrasound.

It is also worth knowing that a measurable gap does not mean you should stop exercising. It means you should exercise in ways that support rather than worsen the linea alba tension, which is exactly the progression described in this article.

Progressing beyond 8 to 12 weeks

After eight to twelve weeks, assuming you are progressing well and have no significant symptoms, you can begin to introduce more challenging exercises: supported squats and deadlift patterns, standing core work, and eventually exercises in more demanding positions. Return to full planks, loaded exercises, and high-impact activity should ideally follow an assessment by a women's health physiotherapist who can confirm the core and pelvic floor are coping with the load.

The goal is a core that is strong, coordinated, and able to manage real-world load, not one that looks good in a mirror but is creating pressure symptoms. These are not competing objectives, but the sequence matters: function first, then strength.

When to see a women's health physiotherapist

A physiotherapy assessment is valuable for anyone postnatally who wants guidance on core rehabilitation, and is particularly important if you have been told you have diastasis recti or if you notice doming at the midline during exercise; if you have pelvic floor symptoms such as bladder leakage, a feeling of heaviness or prolapse, or discomfort; if you had a caesarean and want guidance specific to wound healing and layer-by-layer recovery; if core exercises cause pain; or if you are planning to return to higher-intensity exercise and want to know what is appropriate and when.

In many areas you can self-refer to NHS physiotherapy. Your GP or midwife can also refer you. The wait for NHS physio varies by area, and some people choose to see a private women's health physiotherapist. Either route is worthwhile.

Frequently asked questions

Can I do sit-ups after birth?

Sit-ups and crunches are not recommended in the early postnatal period. They create high intra-abdominal pressure that can worsen diastasis recti and place excessive load on a pelvic floor that is not yet ready. A graduated progression starting with breathing and deep activation is safer and more effective.

What is the linea alba and why does it matter?

The linea alba is the connective tissue that runs vertically down the centre of the abdomen, connecting the two sides of the rectus abdominis muscle. During pregnancy it stretches to accommodate the growing uterus. After birth, it needs to regain tension for the core to function properly.

How do I check for diastasis recti at home?

Lie on your back with knees bent. Place your fingertips horizontally across your midline just above the navel. Lift your head slightly off the floor. If you feel a gap of more than two finger-widths, or if your fingers sink deeply rather than meeting firm tissue, this suggests diastasis. A physiotherapist can assess this more precisely.

What is the transverse abdominis?

The transverse abdominis (TA) is the deepest layer of the abdominal muscles. It wraps around the trunk like a corset and is the primary stability muscle of the core. Reconnecting with it is the foundation of postnatal core rehabilitation.

When can I start planks after birth?

Full planks involve high core and pelvic floor load and are not appropriate in the early postnatal period. Most guidelines suggest waiting until at least 12 weeks and ideally after assessment by a women's health physiotherapist to confirm the pelvic floor and linea alba can tolerate the load.

When should I see a women's health physiotherapist about my core?

A physiotherapy assessment is recommended if you have been told you have diastasis recti, if you have pelvic floor symptoms such as leaking or heaviness, if you had a c-section, if core exercises cause discomfort, or if you want to return to high-intensity exercise and are not sure what is appropriate.

This article is for general information only. Always speak to your midwife, GP, or health visitor if you have concerns about your physical recovery after birth.