In 2011, Vispute and colleagues published a trial in the Journal of Strength and Conditioning Research that should have ended an argument. Twenty-four sedentary adults did seven different abdominal exercises, two sets of ten reps each, five days a week for six weeks. Diet was held stable. At the end, researchers measured abdominal subcutaneous fat, waist circumference and body fat percentage.
Nothing moved. Not the belly fat, not the waist measurement, not the body fat percentage. Abdominal muscle endurance improved. That was the entire result.
Spot reduction does not work, and no amount of core work will reveal muscle that is sitting under a layer of fat. If your goal is visible abs, that is a body composition project involving total calorie intake, and core training is close to irrelevant to it. Once you accept that, core training becomes far more useful, because you can judge it on what it actually delivers.
what it does deliver
The strongest case for core training is back pain and function. A 2023 network meta-analysis in Frontiers in Public Health compared exercise types for chronic low back pain and found core stability training outperformed general aerobic and stretching work on pain and function. Effect sizes in this literature are moderate, not dramatic, and the studies are heterogeneous enough that anyone claiming certainty is overselling. But the direction is consistent across reviews.
The second case is transfer. Your trunk is what transmits force between your hips and your shoulders. A squat, a deadlift, a kettlebell swing and a loaded carry all fail at the midsection before they fail anywhere else, once the load gets high enough. Trunk stiffness is not glamorous but it is the difference between a heavy carry that feels solid and one that folds you sideways.
the sit-up problem
Stuart McGill’s spine biomechanics work at the University of Waterloo is where the anti-sit-up position comes from, and it is worth stating precisely rather than as a slogan. A full sit-up produces lumbar compression in the range of 3,000 newtons and above, which puts it near the 3,400 N action limit that NIOSH uses for occupational lifting. It gets there through repeated flexion of the lumbar spine under load, which is the mechanism most likely to aggravate disc issues in people who already have them.
A plank produces a comparable level of abdominal muscle activation with substantially less spine compression, because the spine stays neutral. That is the argument, and it is a good one.
Where I disagree with how this gets repeated: sit-ups are not dangerous for everyone. A healthy 30-year-old with no back history doing twenty sit-ups is not damaging herself. The case against them is about cost-benefit. You can get the same muscular stimulus with less spinal load, so why choose the version with more? That is different from saying they injure people. Military fitness tests have had recruits doing thousands of sit-ups for decades, and the outcome is mostly sore abs.
a program that fits in eight minutes
The trunk is built for endurance, not one-rep maxes. That means holds and controlled reps, done more often, rather than heavy grinding sets. Three times a week is enough.
| Exercise | Target | Prescription |
|---|---|---|
| Front plank | Anterior trunk | 3 x 20 to 30 seconds |
| Side plank, each side | Lateral trunk, obliques | 3 x 15 to 25 seconds |
| Bird dog | Rotational control, extensors | 3 x 6 to 8 per side, 5 second holds |
| Dead bug | Anti-extension with limb movement | 3 x 8 per side |
| Suitcase carry | Lateral stability under load | 2 x 30 meters per hand |
Those hold times will look short if you have seen the five-minute plank videos. That is deliberate. McGill’s own recommendation is short holds repeated, roughly ten seconds, because form degrades fast and a sagging plank held for three minutes is training your hips to sink, not your abs to brace. If you can hold a plank for two minutes with a flat back, the answer is not three minutes. It is a harder variation: feet elevated, one arm off the floor, or a weight plate on your upper back.
how to tell if you are actually bracing
Most people doing planks are hanging off their shoulder joints and lumbar ligaments. The test: lie on your back, put a hand under your lower back, and press your ribs toward your pelvis until the gap closes without pushing through your feet. That sensation of the abdominal wall tightening all the way around, including the sides, is the brace. In a plank it should feel like someone is about to punch you in the stomach.
If you cannot feel it, your plank is a hold, not an exercise. Shorten the hold until you can maintain the brace the whole time.
the loaded carry is underrated
If I had to pick one movement for a trunk that works, it would be the suitcase carry. Pick up a heavy dumbbell in one hand, stand tall, walk 30 meters without leaning. Your obliques on the opposite side are working hard to keep you upright, your grip gets trained, your posture gets trained, and there is no floor work involved.
Start with something you can carry 30 meters without your torso tipping. Half your body weight in one hand is a reasonable long-term target and most people are nowhere near it. The version people get wrong is leaning away from the weight to counterbalance, which removes the entire point.
breathing, which almost nobody addresses
Holding your breath through a plank is common and it is a problem, because a trunk that can only brace while breath-holding is a trunk that cannot brace during anything that lasts longer than a few seconds. Practice breathing shallowly into your upper ribs while keeping the abdominal wall tight. It feels awkward for about a week and then it becomes automatic, and it carries directly into every loaded lift you do.
If you have an existing back condition, disc diagnosis or ongoing pain, this is a conversation for a physical therapist who can watch you move, not for an article. General core work helps many back pain populations on average, and averages are not a substitute for someone looking at your specific case.