As researchers studied more subjects who were upright and, importantly, alive, their understanding of human strength began to change. “If you really want to understand anatomy and how muscles function, you need to understand what they do while the human body is on two feet moving through gravity,” McCall said. When I asked if he could pinpoint the beginning of the end of the sit-up, he directed me to the work of Stuart McGill, a Canadian biomechanics researcher and arguably, he said, the person most responsible for the sit-up’s demise.
McGill, a professor emeritus at the University of Waterloo, in Ontario, and the author of the book Back Mechanic, didn’t begin his academic career with a particular interest in the sit-up; his work focused on the spine. But throughout the 1990s and 2000s, he led research that changed the way fitness experts thought about exercise. His findings showed that sit-ups and crunches weren’t just mediocre strength-building moves; they were actually hurting lots of people. “If you bend the spine forward over and over again when not under load, not much happens to the spine,” McGill told me. He gave the example of belly dancers, whose movements he has studied: They flex their spines repetitively without high incidence of injury. “The problem occurs when you flex over and over again with load from higher muscle activation or external objects held in the hands.”
If you’ve ever been told to lift with your legs, this is why. When a person’s spine curves and strains in order to move weight through space—like when a bunch of third graders flail through a set of sit-ups—the movement stresses their spinal disks. The more often you ask your spine to flex in those circumstances, the riskier it is. This is how people who spend their working lives moving inventory around a warehouse or stacking bushels of produce onto trucks end up with back pain later in life, even if they can’t point to any acute back injuries suffered along the way. McGill found that the most reliable way to avoid this kind of chronic problem is to brace your core when you pick up something heavy. That means tensing key muscles in order to protect your spine’s structural integrity, and to help shift the effort to your hips and legs. Not coincidentally, weight lifters follow this advice when they safely execute a dead lift. Perfect form is not always possible for workers dealing with irregular loads and crowded spaces, but intentional exercise is all about form. Getting it right and activating the intended muscles is the whole point. »