Everybody seems to want abs and better core strength, but crunches simply don’t do what people are wanting them to do. It’s time to stop wasting time on them. Here’s why, as well as some good core strengthening alternatives:
There is no such thing as localized fat burning, so doing core exercises will not burn fat on your stomach. “But if I have a more muscular core, won’t it look better anyway?” Yes, but:
There’s not enough resistance in a crunch to build any muscle. Anything you can do more than 20 or 30 reps of is going to build you little to no muscle. You’re just developing endurance in the currently existing muscle at that point. The point of added muscle is to give your skeleton greater structural integrity under load. If there’s no load, there’s no need for more muscle. “But if I do crunches I’ll burn calories, which will help me burn fat, right?” Yes, but
Crunches burn very few calories. Crunches have a short range of motion and recruit relatively little muscle tissue, meaning the calories you burn are going to be nominal. For the purpose of burning calories, you would be much better off doing squats, deadlifts, push ups, pull-ups, running… or pretty much anything else. “But I heard that core endurance is good for athletic performance?” Yes, but
You’re training your core wrong. Your core is primarily meant to stabilize your spine and provide a strong foundation from which the rest of your body can generate force. It is not supposed to generate much force itself. This is why the strongest lifts ever done and the greatest force production achieved by humans has been accomplished with the hips and with a stiff, stable core. For example, suppose you try to press a heavy weight overhead but your back buckles and and hyper-extends. You will not be able to press as much weight and will be at risk of injury. If a huge construction crane, capable of lifting thousands of pounds, is mounted on a giant pile of spaghetti, it’s not going to be able generate any force. It’s just going to fall over. Proximal stability enhances distal force.
So what should you do instead? Your core exercises should primarily consist of exercises like planks, side planks, properly executed anti-rotational exercises like the oblique twist, bird dogs or variations of these exercises. Exercises like pushups, single arm farmers carries and dumbbell rows (stiff torso) also require a fair amount of core stabilization. Core exercises should be set up to resist force, not create it.
Now go forth and plank.
Bonus note: Priming your core with exercises like the plank has been shown to increase core stability immediately for up to two hours after doing them. Sprinters who primed their core prior to sprinting were able to sprint faster than they could without core priming. Add sub-maximal core activation into your warm-up prior to compound movements and see if you feel a difference.