I can't tell you how many times a client has grabbed the skin around her belly button, pinched it, and said something like "I don't think my core will ever come back together." Usually she's a mom, a few months or a few years postpartum, and somebody on the internet told her she has a "mommy pooch" she just needs to crunch away. That's not what's happening, and crunching it away is honestly bad advice. What she's describing has a real name — diastasis recti — and real research behind how to test for it and what to actually do about it.
I already wrote about pelvic floor health and how it connects to core training, and I touched on diastasis recti briefly in that one. This post is the deep dive I promised. No bro science, no Instagram myths — just what the physical therapy and exercise science literature actually says about testing yourself and training around this safely.
What's Actually Happening In There
Your two rectus abdominis muscles — what people call the "six-pack" — run parallel down the front of your stomach, connected down the middle by a band of connective tissue called the linea alba. During pregnancy, your growing uterus stretches that connective tissue to make room. For most women, it widens some amount, and that's completely normal — it's not a muscle tear, and it's not something you did wrong. Diastasis recti is simply when that midline gap stays wider than it should months after delivery, which can leave your core feeling weaker and show up as that "pooch" that doesn't respond to regular ab work.
Here's the thing I want you to understand before we go any further: this is a connective tissue and pressure-management issue, not a "your abs are too weak" issue. That distinction changes everything about how you should train it.
How to Actually Test Yourself at Home
You don't need a trainer or a doctor's office to get a reasonable first read on this. Lie on your back, knees bent, feet flat on the floor. Lift your head and shoulders slightly off the ground like the very start of a crunch, just enough to engage your abs. Place your fingertips at your belly button, pressing gently into your midline, and feel for a gap. Then check a couple inches above and below your belly button too, because the gap isn't always uniform.
A one-to-two finger-width gap is considered within the normal range for most women. Wider than that, or if you feel a noticeable depth to the gap (your fingers sink in) or a dome/bulge pushing up along your midline when you engage your core, that's worth paying attention to.
Now, how much should you trust that test? A 2016 systematic review in Manual Therapy by van de Water and Benjamin looked specifically at this. They found finger-width palpation has solid consistency when the same person checks it the same way over time (reliability scores of 0.73-0.77), but it's noticeably less consistent when two different people are the ones doing the testing. Translation: this self-check is genuinely useful for tracking your own progress over weeks and months, but don't panic over a half-finger difference between how you measured it and how your sister or your doctor measured it. Stay consistent with your own method and track the trend.
The Exercises the Research Actually Supports
A 2023 randomized controlled trial published in the Korean Journal of Family Medicine gives us one of the clearest pictures we have. Researchers put postpartum women through an 8-week progressive program — they called it the Split Tummy Exercise Program — and compared it to women doing standard postpartum walking and general movement. The structure mattered as much as the exercises themselves: weeks 1-4 were isometric ab bracing, gentle limb movements while holding that brace, nothing fancy. Weeks 5-6 added pelvic tilts and bridging. Only in weeks 7-8 did they progress to crunches, planks, and rotational work like Russian twists.
The results: the exercise group closed their gap by 6.17mm on average — a 27% reduction — compared to a non-significant 1.66mm in the control group. That's a real, measurable difference, and it came from a program that earned its way up to harder movements instead of jumping straight to crunches on day one.
What the Research Says About Crunches (And Why It's More Nuanced Than You Think)
This is the part that surprises people, including me the first time I read it. A 2015 study in the Journal of Orthopaedic & Sports Physical Therapy used ultrasound to measure what actually happens to the gap during two different exercises: the classic abdominal crunch and the gentler "drawing-in" maneuver (pulling your belly button in toward your spine). Across nearly all the women and time points they measured, the crunch produced a significant narrowing of the gap in the moment — sometimes a lot more narrowing than the drawing-in exercise did.
I'm not telling you to go do crunches tomorrow. What this tells us is that the old blanket rule — "never do a crunch again if you have diastasis recti" — oversimplifies things. The real risk factor isn't the crunch itself, it's what your midline does under pressure. If you see or feel that dome/bulge pushing up along your linea alba when you engage, that's your pressure-management system failing under that load, and that's the signal to back off and rebuild your foundation first — which is exactly why the successful program above started with isometric bracing for four weeks before touching a crunch.
The Takeaway
Diastasis recti is physiology, not a personal failure, and it's not something crunches alone will fix or flare up in some permanent way. The research actually supports a pretty simple progression: learn to brace and manage your intra-abdominal pressure first, build that for several weeks, and only then start layering in more demanding flexion work like crunches and planks, watching the whole time for doming along your midline as your stop sign. Test yourself the same way every time so you're tracking real change, not measurement noise. And don't expect overnight results — the best controlled research we have shows meaningful, real improvement over 8 weeks of consistent, progressive work, not a weekend fix.
References
- Benjamin, D. R., van de Water, A. T. M., & Peiris, C. L. (2014). Effects of exercise on diastasis of the rectus abdominis muscle in the antenatal and postnatal periods: a systematic review. Physiotherapy, 100(1), 1-8.
- Mota, P., Pascoal, A. G., Carita, A. I., & Bø, K. (2015). The Immediate Effects on Inter-rectus Distance of Abdominal Crunch and Drawing-in Exercises During Pregnancy and the Postpartum Period. Journal of Orthopaedic & Sports Physical Therapy, 45(10), 781-788.
- van de Water, A. T. M., & Benjamin, D. R. (2016). Measurement methods to assess diastasis of the rectus abdominis muscle (DRAM): A systematic review of their measurement properties and meta-analytic reliability generalisation. Manual Therapy, 21, 41-53.
- Shohaimi, N. A. I. M., et al. (2023). Split Tummy Exercise Program for Reducing Diastasis Recti in Postpartum Primigravidae: A Randomized Controlled Trial. Korean Journal of Family Medicine, 44(2), 102-108.
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