Contrary to what you may read in most fitness magazines, the conventional sit-up is quite possibly the most overrated exercise ever created for the core. That’s a big statement to begin a fitness article with, I know, but researchers from the Department of Kinesiology at the Pennsylvania State University have set out to prove exactly why this is the case. They tested whether larger, compound exercises like the plank were better for you in your quest for a six-pack compared to smaller, isolation exercises like the standard sit-up. The results may have you rethinking your core training routine ready for the summer.
First, large compound exercises like the plank and all its variations mainly engage what’s known as the ‘proximal limb’ muscles as well as the ‘primary trunk’ muscles of the core. ‘Proximal limb’ muscles are mainly the shoulders (deltoids) and gluteals, and the ‘primary trunk’ muscles are those of the stomach and lumbar spine (back). Smaller, more isolated movements like the sit-up only really engage the ‘primary trunk’ muscles. In the past there hadn’t been much research to determine which is better for engaging the muscles of the core, compound exercises or isolation exercises, and this is exactly what the American sports scientists wanted to find out.
After recruiting 20 athletes, scientists had them complete a series of core exercises while each was connected to surface electromyography (EMG) electrodes. This then measured the muscle activation in the core as they performed both compound movements and isolate movements. The results revealed activation of the abdominal and lumbar muscles were higher during the compound movements. Specifically, the compound ‘Plank with Reach’ exercise showed a 20% greater activation in the rectus abdominis muscle compared to the isolation standard ‘crunch’. On top of this, anterior deltoid, erector spinae, and gluteus maximus activities were two times greater. This was supported by results that showed the compound ‘side plank’ increased external oblique activity by 25% compared to the isolation ‘side crunch’ movement.
What this means is that according to Pennsylvania State University research, your core training should mainly consist of compound exercises like the plank. That’s not to say isolation movements aren’t without their benefits, but it does mean that a core routine that is heavily based around crunches and sit-up variations might need to be redesigned. So what else should you do if you can’t rely on sit-ups?
First, as is obvious from the aforementioned study, try including more planks in your routine. It will engage the muscles of the core more – and won’t give you a bad back from doing thousands of sit-ups. If you find they’re becoming too easy, why not try making them unstable planks? A topic that’s been researched a lot in strength and conditioning circles in recent years is this concept of unstable surface training. While research published by the National Strength and Conditioning Association acknowledge its “application is still very limited”, and gyms the world over are filled with personal trainers performing impressive but arguably useless circus-like exercises with swiss balls, unstable surface training has been shown to increase core muscle activity. For this reason, try performing your planks with TRX equipment or on a swiss ball or medicine ball – essentially anything unstable that will shock the abs into working over a different range of motion.
Finally, to throw a ‘curve ball’ into the mix, research published in the Complementary Therapies in Medicine Journal used surface electromyographic technology to measure muscle activation in the upper rectus abdominis and lower rectus abdominis during eleven yoga poses. Specifically, these were: Halfway lift, Forward fold, Downward-facing dog, Upward-facing dog, High plank, Low plank, Chair, Mountain with arms down, Mountain with arms up, Warrior 1 (both sides). What they found was, the high plank, low plank and downward-facing dog poses are particularly effective for strengthening the external oblique muscles.
So there you have it, the fitness industry’s big fat six-pack myth. I must point out that even with all the plank variations in the world, your nutrition and diet really determines how to get a six-pack since it’s this that lowers your body fat enough for your abs to appear visible. But that is a whole other article – for now I hope this one shows you how sit-ups aren’t the great stomach exercise many people think they are.