The primary mechanical action of the rectus abdominis isn’t debated. It brings the rib cage and pelvis CLOSER together, invoking a position called spinal or trunk flexion. I have actually searched to find one single photo of one famous fitness personality who has ever once performed a plank with a flexed trunk instead of an extended spine. I’m still searching.
Every infomercial creator, every workout video series, every time, the way they personally perform “abs” or the way they coach “abs” is almost exclusively with an extended spine. When they are in a plank, the back looks like the letter “u”. When they are lying on their backs for leg raise or some such movement, there’s a visible space under the section of the back between the hips and shoulder blades. These positions are not the action of the abs. This isn’t my opinion. Look up the defined action of the rectus abdominis in any legitimate textbook or, heck, even on Wikipedia.
“They get results, so it can’t be THAT bad,” you may be thinking. Well, there are three logical fallacies embedded in that thought -
One: that thought is assuming something without considering the PERCENT effective outcome for highly marketed fitness programs. One thousand testimonials (if they are even real and not paid-for fakes) doesn’t rise to statistical significance if there were one million buyers/users. At the big box clubs, the stats are that at least one out of ten people doing something wrong will still succeed in the short term by accident. So, if a famous program has a hit rate of one in a thousand (1,000 out of 1,000,000 users), they are demonstrably sabotaging even people who would’ve succeeded just by moving their bodies more.
Two: connected to the first is something called sample/survivor bias. We see people who survived bad methodology and we incorrectly attribute success to that defective program. We don’t get to see all the injured people. Or, if we consider the injured people, we lay the blame at their feet for “using bad form.” Yet, as I just stated, the way core exercises are popularly taught is bad form. The spine is supposed to flex when loading abs. Technically, the success testimonials are probably people who didn’t follow the instructions well. And the injured people likely did execute the program as instructed.
Three: if you lookup forums for injuries from popular fitness videos, you’ll find there are numerically far more people on these than all of the showcased success stories combined. And of course this is the case, because, as I stated, the primary mechanical action of the rectus abdominis is not a controversial topic among people educated on exercise science and physiology.
For advanced movement practitioners, we are correcting this in people all the time. Even for high level athletes I coach, abs are excessively long and hip flexors/low back are excessively short. It’s a pandemic. And even newbie trainers and coaches who pay attention can see this propensity. The origin of psoas major (a hip flexor) is the lumbar spine. As people work hip flexion while the back is hyperextended, the risk of pain, irritation and injury go up. The way even decent coaches teach sprinting, jumping, squat and other structural lifts amplifies this imbalance. The vast majority of exercise tweaks and injuries could’ve been avoided if popular voices in the fitness world understood neutral ranges, sequential activation, and non-debated muscle action.
Any fool can throw together a series of movements which get people to sweat. Taking years to obsess about biomechanics and how to prevent or troubleshoot orthopedic issues is a whole other domain of expertise. And, unfortunately, it doesn’t look like any of the famous fitness personalities took that time to develop professionally before cobbling together a well-marketed workout series.