Exercise will never go out of style, but fitness trends are constantly evolving. Take the sit-up: Hailed for decades as the best way to sculpt six-pack abs, the famous floor move is now in the hot seat, with some fitness experts calling it baseless and even dangerous.
Related: The 4-Week Plank Challenge
"People believe sit-ups are the magical route to developing a six-pack, but they're not a quick fix for several reasons," says Nadia Murdock, a certified fitness trainer at 24 Hour Fitness in New Jersey.
Nutrition Is Key for Flat Abs
"Genetics play a role, so if you tend to carry more weight in your stomach, it's going to be a lot harder to sculpt your abs," Murdock says. A clean and calorie-controlled diet is also key. And keep in mind that you won't burn belly fat by endlessly crunching your midsection; only a full-body cardio workout will accomplish that.
Sit-ups have also been blamed by Harvard Medical School and the American Council on Exercise, among others, for lower-back pain and disc damage. One study published in the Journal of Strength and Conditioning Research even deemed them a time suck that yields little results. Even the Navy banned the move from its biannual physical fitness test in 2015.
How the Sit-Up Fell From Grace
So what happened to the sit-up, once considered the workout du jour, thanks to classic videos like "Abs of Steel" and Cindy Crawford's "Shape Your Body"? For starters, there's been a disconnect between what happens in the gym and in the laboratory.
Stuart McGill, Ph.D., a world-famous back expert whose team was the first to measure the mechanics of the sit-up, has doubted the move for decades. "We initially had difficulty publishing our research on the dangers of sit-ups because it was heresy," said the professor of spine biomechanics at the University of Waterloo in Ontario, Canada. "People just wanted a six-pack."
According to McGill, whose research prompted the U.S. military to drop the sit-up, the floor move creates an effect called fatigue loading. "If you bent a thin tree branch, it wouldn't break," he says. "But if you bent a thick, strong branch, it would crack."
Your midsection is like the strong branch. That's because your knees, legs, shoulders and hips are designed to bend back and forth — muscles of the spine, core and torso are not.
Experts Question the Sit-Up's Effectiveness
Trendy abdominal machines were in part designed to relieve the pain associated with sit-ups and facilitate movement with less effort, according to Cris Dobrosielski, spokesperson for the American Council on Exercise and owner of Monumental Results in San Diego. However, the get-ripped-quick contraptions that sold on infomercials (remember the Ab Lounge and Ab Rocket?) were no better, and likely worse, for the back.
Toward the early 2000s, in part due to McGill's work, fitness trainers began addressing the safety of the sit-up and moving toward functional fitness, the idea that exercise should train muscles used in real-life, daily activities.
"People still wanted to look good, but there was also an emphasis on moving better," says Dobrosielski. "Crunching at the waist isn't very functional." Still, educating the public that sit-ups aren't ideal was a work in progress.
Today, planking and squats are generally considered optimal ways to tone the mid-section while simultaneously strengthening other parts of the body as a whole. If you love floor work, check out the McGill curl-up (named for world-renowned spinal researcher Stuart McGill), a move designed to define the entire core while protecting the back and preventing pain.
What Do YOU Think?
What is your favorite core exercise? Do you do a variation on a crunch or sit-up? What healthy eating habits do you follow in order to keep belly fat at bay?