During the Army Physical Fitness Test (APFT), soldiers perform push-ups, sit-ups, and a two-mile run to demonstrate that they're physically qualified for duty. In a 2005 study, researchers found that although only 117 soldiers out of more than 1,500 sustained injuries during the test, a whopping 56% of those injuries were caused by sit-ups. This is no surprise to many: everyone from biomechanics experts to celebrity trainers have stopped recommending sit-ups because of their high potential for injury. According to Dr. Stuart McGill, professor of spine biomechanics at the University of Waterloo, sit-ups and crunches place up to 750 pounds (340 kilograms) of compressive force on the spine, which can lead the discs between the vertebrae to bulge and even herniate, pressing on nerves and causing serious back pain. What's more, they're not even that useful: the core muscles are primarily there to stabilize the torso, not flex the spine, so the strength gained from a flexing exercise like the sit-up has very few uses in the real world. That's why trainers and physicians are recommending the plank and other stabilizing exercises to help people build stronger cores.
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Key Facts In This Video
Sit-ups can lead to herniated discs in the spine and cause back pain. 00:13
Here are several alternate core-strengthening exercises. 00:42
If you did hundreds of sit-ups, your discs would break before your spine had a chance to catch up. 02:38