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Crunches weaken your core, mess with your alignment and set you up for back pain and pelvic floor dysfunction.

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You've probably included the crunch in your exercise regimen at some point, maybe even currently. They've been a staple at the gym for years, but I cringe every time I see someone doing them, especially women. It's about time everyone knew the truth about crunches and why they aren't the exercise for you.

1. Crunches load your spine at an equivalent of 340 kilograms of compressive force. This is over and above the maximum recommended by the U.S. National Institute for Occupational Safety and Health. For an exercise that was supposed to help eliminate back pain by strengthening the core, crunches have only worsened the back-pain epidemic.

2. When performing a crunch, the work is being done by the superficial muscles in the abdomen and the hip flexors, which shorten and tighten with each repetition. But here's the thing: These muscles are already short and tight thanks to all the sitting we do in our daily lives, so it makes no sense to further shorten and tighten them. Crunches only weaken your core, mess with your alignment and set you up for back pain and pelvic floor dysfunction such as incontinence and, for women, pelvic organ prolapse, which is the descent and eventual protrusion of an organ into and out of the vagina.

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3. Crunches do not make your tummy flat. Next time you are at the gym, watch people doing crunches and pay attention to their abdomen – you will notice the tummy pooches outward, which is the opposite of the so-called purpose of this exercise. You will also notice that the shoulders round, the head tucks forward, the butt tucks under and the breath is often held. This is disastrous to the core and pelvic floor and only serves to exacerbate the terrible posture we live in all day.

4. Crunches cause downward pressure on the pelvic floor and outward pressure on the abdominal wall, which can contribute to a condition known as diastasis recti (a separation of the outermost abdominal muscles) in both men and women. That's right – men can get it, too.

5. Research has shown that as many as 52 per cent of women with pelvic floor dysfunction have diastasis recti. This stat is alarming, especially given that women can have diastasis recti after pregnancy but have no idea. So when they start doing

crunches in an attempt to lose their mummy tummy, they make their existing diastasis worse by putting outward pressure on the weakened abdominal wall. The pressure also bears down on the pelvic floor and puts them at greater risk of chronic back pain, incontinence and pelvic organ prolapse.

6. When you do a crunch, the pressure inside the abdominal cavity increases and, in a dysfunctional core, the ability to manage this increase in pressure is hindered. This results in the internal organs being pushed down. Pelvic floor physiotherapist Julia Di Paolo of PhysioExcellence in Toronto has seen a consistent increase in prolapse and believes it is caused in large part by our increasingly sedentary lifestyles, the rise of challenging exercise programs such as CrossFit and boot camps, and the lack of awareness about core exercise in pregnancy and postpartum recovery. "Crunches are a part of every 'hard-core' exercise program out there and are often one of the first exercises a new mom will choose in an attempt to get her body back," Di Paolo says. "New moms, and most people who sit for a living – which is most of us – do not have the core strength or stability to withstand the demands of most mainstream fitness programs and they end up in my office with a condition that will dramatically affect their quality of life and which activities they can do."

So instead of crunching your way to oblivion, I urge you to take a step back. If it's a flat tummy you are after, begin with optimizing your alignment during everyday activities such as sitting and walking – position your ribs over your pelvis, keep your tailbone untucked and balance your weight over your feet rather than the forefoot. Move more, sit less and exercise your pelvic floor in isolation to start, then progress to dynamic movements such as bridges, squats and lunges. Choose exercises that restore your body instead of break it down.

Kim Vopni, known as The Fitness Doula, is a certified pre/postnatal fitness consultant, co-founder of Bellies Inc. and owner of Pelvienne Wellness Inc.

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