The postpartum crunch myth: Are crunches really bad for abdominal separation?
If you've had a baby, you may have been told to avoid crunches, sit-ups and anything that makes your abdominal muscles work too hard.
The concern? That these exercises will pull your abdominal muscles further apart, worsen diastasis recti and place too much pressure on your recovering core .
But what if the relationship between abdominal exercise and abdominal separation is more complicated than we've been led to believe?
Ultrasound research has shown that crunches can actually narrow the gap between the abdominal muscles during the exercise itself. More recently, a small Australian pilot study investigated whether introducing gentle crunches during the early postpartum period could improve abdominal separation compared with deep abdominal activation alone.
The results were promising.
So, should we still be telling every new mother to avoid crunches for the first six weeks after birth?
The answer is more nuanced than a simple yes or no.
Understanding abdominal separation after birth
Abdominal separation, also known as diastasis recti abdominis, is the increased distance between the two rectus abdominis muscles that run vertically along the front of your abdomen.
The connective tissue joining these muscles is called the linea alba. During pregnancy, this tissue stretches to accommodate your growing baby.
After birth, the abdominal wall gradually adapts and recovers. The distance between the muscles often reduces naturally over time.
Abdominal separation is common and does not automatically mean your abdominal muscles are damaged or that you have a weak core.
However, some women experience reduced abdominal strength, difficulty managing load, discomfort or reduced confidence when returning to exercise.
This is why postpartum rehabilitation should look beyond the size of the gap alone. We also want to restore abdominal strength, coordination and the ability to manage the demands of everyday life.
What does ultrasound research tell us about crunches?
Researchers have used real-time ultrasound to investigate how different abdominal exercises affect the distance between the rectus abdominis muscles.
The findings challenge the traditional assumption that crunches necessarily pull the abdominal muscles further apart.
1. Crunches can narrow the gap during exercise
A study by Mota and colleagues investigated the immediate effects of abdominal crunches and abdominal drawing-in exercises during pregnancy and the postpartum period.
The researchers found that crunching generally reduced the inter-recti distance during the movement. In contrast, abdominal drawing-in produced a different response and could increase the measured distance at some locations.
This is an important distinction. The abdominal wall responds differently depending on which muscles are activated and how the movement is performed.
However, a smaller gap during a contraction does not automatically mean better abdominal function, nor does it prove that crunches will permanently close the gap.
It tells us that abdominal exercises have different mechanical effects, and that we should not judge an exercise solely by the assumption that it will pull the muscles apart.
2. Is drawing your stomach in always better?
Traditional postpartum core rehabilitation has often emphasised drawing the belly button towards the spine to activate the transversus abdominis, the deeper abdominal muscle that wraps around the trunk.
This can be a useful exercise, but it is not necessarily the best starting point for every woman or the only way to rehabilitate abdominal separation.
Research by Lee and Hodges examined how the linea alba behaved during curl-ups, including the effect of activating the transversus abdominis.
Their work highlighted that the distance between the muscles is only one part of the picture. The shape and deformation of the linea alba during contraction may also influence how forces are transferred across the abdominal wall.
The takeaway? Abdominal rehabilitation is not simply about closing a gap or learning to draw your stomach in. We also need to consider abdominal wall tension, strength, coordination and function.
The promising Australian study: Crunches in the early postpartum weeks
One of the most interesting studies in this area is a pilot randomised controlled trial by Simpson and Hahne, published in Physiotherapy Canada in 2023.
The researchers compared two approaches to early postpartum abdominal rehabilitation in 44 women with abdominal separation following vaginal birth.
One group performed a brief rectus abdominis crunch, while the other performed isolated transversus abdominis activation.
The findings were encouraging:
The crunch group experienced a greater reduction in the measured abdominal gap at several sites at 6 and 12 weeks postpartum.
No adverse events were reported during the trial.
The results suggested that gentle rectus abdominis activation may be a useful option during early postpartum rehabilitation.
This is particularly relevant because the study investigated an actual early postpartum exercise programme rather than simply measuring the immediate effect of a crunch during ultrasound.
It challenges the blanket assumption that all abdominal flexion must be avoided during the early weeks after a vaginal birth.
However, the results should be interpreted carefully. This was a small pilot study, and follow-up was incomplete. Larger studies are needed to confirm the findings and determine which women are most likely to benefit.
The study also does not establish that early crunches are appropriate following caesarean birth.
What does this mean? Gentle, appropriately prescribed abdominal exercises may be worth considering earlier than traditional advice suggests for some women after vaginal birth. They should not be automatically prescribed to every new mother, regardless of her recovery.
Do crunches actually improve abdominal separation?
A further randomised controlled trial by Gluppe and colleagues, published in the Journal of Physiotherapy in 2023, investigated a 12-week abdominal exercise programme involving head lifts, curl-ups and twisted curl-ups.
The study involved 70 women who were 6–12 months postpartum and had diagnosed diastasis recti.
The researchers found that the exercise programme improved abdominal muscle strength and thickness without worsening the measured abdominal separation.
Together, these studies challenge the idea that crunches are inherently harmful for women with abdominal separation.
However, the studies examined different populations and exercise programmes. The later-postpartum trial cannot establish the safety of beginning crunches in the first days or weeks after birth, while the early pilot trial needs further confirmation.
The emerging evidence supports a more individualised approach, rather than a blanket rule that crunches are always harmful or always beneficial.
Is closing the gap the most important goal?
Not necessarily.
The distance between the abdominal muscles is only one measure of abdominal separation. It does not tell us everything about how your abdominal wall functions.
We also need to consider:
Linea alba tension: How the connective tissue responds when your abdominal muscles contract.
Abdominal strength: Your ability to generate and sustain force.
Coordination: How your abdominal muscles work with breathing and the pelvic floor.
Load management: Your ability to manage the demands of lifting, carrying, exercising and everyday parenting.
Symptoms: Whether you experience abdominal discomfort, pelvic heaviness, vaginal pressure or urinary leakage.
A narrower gap during exercise does not automatically mean better function. Equally, a wider gap during a particular contraction does not automatically mean an exercise is harmful.
Our goal is to restore comfortable function, build strength and help you return confidently to the activities that matter to you.
When can you start abdominal exercises after birth?
The right starting point depends on your birth experience, healing, symptoms and individual capacity. Gentle abdominal activation and more demanding exercises such as crunches should not be treated as interchangeable.
Weeks 0–2: Gentle abdominal connection
After an uncomplicated vaginal birth, gentle abdominal activation may be appropriate during the early postpartum period, alongside comfortable breathing, walking and pelvic floor exercises when suitable.
Australian postnatal exercise guidance from Pelvic Floor First includes abdominal muscle bracing, walking and pelvic floor exercises during the first three weeks after birth.
View Australian postnatal exercise guidance.
Gentle abdominal connection
Begin lying on your back with your knees bent, or lie on your side in a comfortable position.
Breathe in gently, allowing your ribs and abdomen to move naturally.
As you breathe out, gently engage your lower abdominal muscles using a light effort.
Continue breathing normally without forcefully pulling your abdomen in or holding your breath.
Relax your abdominal muscles as you breathe in.
Repeat 5–8 times if comfortable.
The aim is to reconnect with your abdominal wall, not to create a strong contraction or force the abdominal gap together.
Gentle abdominal activation can form part of early recovery, but this does not mean crunches need to be introduced immediately. If you have significant perineal trauma, pain, difficulty relaxing your pelvic floor or complications following birth, seek individual advice before progressing.
Weeks 2–4: Build comfortable movement and control
As your recovery progresses, you may gradually introduce gentle functional movements.
Options may include:
Pelvic tilts.
Heel slides.
Supported sit-to-stands.
Gradually increasing walking.
Continued breathing and abdominal coordination exercises.
Some women may be ready to progress their abdominal exercises earlier than others. However, there is no universally established week at which every woman should begin crunches.
A postpartum abdominal and pelvic floor assessment can help guide exercise selection and progression, particularly if you have symptoms or concerns about your recovery. This is included in our Postpartum Rebalance Osteopathy and Postpartum Pelvic Health appointments.
Weeks 3–6: Progress according to your recovery
As you approach six weeks postpartum, you may gradually increase the challenge of your abdominal and functional exercises if healing is progressing well.
A head lift or small-range curl-up may be considered individually, but it should not be prescribed automatically based on the week alone.
Your clinician may assess your breathing, abdominal wall response, symptoms, movement control and ability to manage load before recommending progression.
Visible doming along the abdominal midline can be useful information, but the absence of doming alone does not guarantee that an exercise is appropriate for everyone.
The same principle applies to pelvic floor symptoms. Pain, heaviness, vaginal pressure or urinary leakage are reasons to modify exercise and seek advice.
The six-week postnatal check is an opportunity to discuss your recovery and plans to return to exercise. It is not an automatic clearance for every type of abdominal exercise.
What about planks, sit-ups and mountain climbers?
These exercises are not necessarily off-limits forever. However, they place different demands on the abdominal wall and pelvic floor and may require more preparation than gentle abdominal activation.
Australian guidance from Pelvic Floor First recommends an abdominal muscle and/or pelvic floor assessment before performing sit-ups, curl-ups, planks, hovers and mountain climbers after birth.
The aim is not to create fear around movement. It is to help you identify an appropriate level of challenge and progressively build towards more demanding exercise as your recovery allows.
What if you had a caesarean birth?
Recovery after a caesarean birth requires additional consideration because your abdominal tissues have undergone surgery as well as the changes of pregnancy.
During the early weeks, prioritise:
Comfortable breathing and gentle mobility.
Short walks as medically appropriate.
Gradual increases in everyday activity.
Wound healing and comfortable transfers in and out of bed.
Progress abdominal activation according to your pain, incision healing and overall recovery. Avoid forceful contractions and movements that cause pulling or discomfort around the incision.
Do not begin scar massage until the wound is fully healed and scar mobilisation is appropriate.
Although the research challenges the blanket prohibition on crunches for abdominal separation, it does not establish that early crunches are appropriate after caesarean surgery.
There is no universal timeline for returning to crunches after a caesarean birth. Your readiness should be guided by healing, symptoms and individual clinical advice. At Empower Osteopathy we also offer Cesarean scar release and education using myofascial cupping, needling, massage and Ghu sha.
The bottom line: Your abdominal muscles need rehabilitation, not fear
The evidence is challenging the old idea that crunches automatically worsen abdominal separation.
Ultrasound studies show that the abdominal gap can narrow during a crunch. An early postpartum pilot study found promising results for gentle crunches compared with isolated deep abdominal activation, while a separate trial found that a later-postpartum curl-up programme improved abdominal strength without worsening separation.
These findings do not mean crunches are the best exercise for everyone or that they should be started immediately after birth. More research is needed, particularly around early postpartum exercise progression.
The goal is to restore abdominal function, build strength progressively and choose exercises that suit your stage of recovery.
You do not need to fear every movement that makes your abdominal muscles work. You do need a sensible progression that considers your birth experience, healing, symptoms and goals.
Postpartum recovery at Empower Osteopathy
At Empower Osteopathy on the Gold Coast, we support women through pregnancy, postpartum recovery and pelvic health with an individualised approach to movement and rehabilitation.
If you are concerned about abdominal separation, unsure which exercises are appropriate or preparing to return to the gym after birth, a postpartum assessment can help you understand your abdominal wall and pelvic floor function and develop a plan suited to your recovery.
Book a postpartum assessment with Empower Osteopathy to discuss your recovery and your return to exercise.
This article is intended for general education and does not replace individual medical advice. Postpartum exercise should be adapted to your birth experience, healing and symptoms.
References
Mota P, Pascoal AG, Carita AI, Bø K. (2015). The Immediate Effects on Inter-rectus Distance of Abdominal Crunch and Drawing-in Exercises During Pregnancy and the Postpartum Period.
Lee D, Hodges PW. (2016). Behavior of the Linea Alba During a Curl-up Task in Diastasis Rectus Abdominis: An Observational Study.
Simpson E, Hahne A. (2023). Effectiveness of Early Postpartum Rectus Abdominis versus Transversus Abdominis Training in Patients with Diastasis of the Rectus Abdominis Muscles: A Pilot Randomized Controlled Trial.
Gluppe SB, Ellström Engh M, Bø K. (2023). Curl-up exercises improve abdominal muscle strength without worsening inter-recti distance in women with diastasis recti abdominis postpartum: a randomised controlled trial.
Pelvic Floor First. Returning to sport or exercise after birth. Australian postnatal exercise guidance.
