Abdominal Exercises: Are You Doing Too Many Reps?

image of Cathe and Cedie working their abs

Have you ever watched people in an exercise class doing abdominal exercises on a mat? Oftentimes, they’re madly crunching their abs in a fevered attempt to do as many reps as they can in some allotted time. The focus is on volume rather than increasing the time the abs are under tension or the resistance they’re forced to work against. It’s common to see this approach being used – but is it really the best way to build abs?

How Your Abdominal Muscles are Arranged

First, let’s look at the anatomy of your abs, the muscles you’re trying to make more defined. You have your superficial rectus abdominis muscles, a long, flat muscle that extends vertically from your ribs to your pubic bone. You also have two external obliques that lie superficially on each side of the rectus abdominis. Underneath the external obliques lie the internal oblique muscles. The internal and external obliques work together to rotate your trunk and flex your spine to one side or the other.

At a deeper level, you have the deep transversus abdominis muscle layer, the layer we often ignore when we train. The transversus abdominis has the job of helping to hold your internal organs in place and stabilizing your spine. Strengthening this muscle will help hold your tummy in and improve your posture. It’s a muscle that’s too important to disregard!

So, how should you work these muscles? A balanced workout will target all of these muscles and do it in a way that’s not harmful to your back. Most people do a predominance of abdominal exercises that involve spinal flexion, like basic crunches, reverse crunches, and their variations. The problem is these exercises cause repeated flexion of the spine. That’s not healthy, especially if you have a history of back problems.

A balanced workout would include a modest number of spinal flexion exercises and, then, only if you have a healthy back, as well as few rotation exercises to target the obliques. The rest would be stability exercises, such as planks and plank variations and back extension exercises, like the classic Superman movement and bird dog extensions. We often neglect the muscles in the back, but when we work the abs, we need to balance things out by working the opposing muscles.

What about Reps?

Here’s where most people get it wrong. Your ab muscles are like other muscles on your body. They hypertrophy when you work them against resistance and use progressive overload. If you’re trying to get abdominal definition, you have to make the superficial muscles in your abs, mostly the rectus abdominis, larger and more defined AND reduce the tummy fat that covers your ab muscles.

There’s a common misconception that doing hundreds of crunches will make the ab muscles more defined AND lead to loss of belly fat. The truth is that this approach is not effective for either. If you train any other muscles this way, little resistance and lots of reps, you increase muscle endurance but will do little to increase the size of the muscles. Plus, working small muscle groups, like the abs, with high reps doesn’t burn much body fat either.

So, the high-rep approach to training your abs, lots of crunches, won’t help you reach your goal. In fact, it might hurt your back. A better approach is to do 10 to 15 reps when you do crunches, and slow down the movement down, so you’re holding the muscles under tension longer. Contract your abs and use a slow, controlled motion to move through each repetition. Hold the crunch for one to two seconds at the top of the movement before returning to the starting position. When you see people doing 30 or 40 crunches at a time, they’re usually using sloppy form and lots of momentum. Neither will help you achieve your goal and both increase the risk of injury.

Once you can easily to 10 to 12 reps, make the exercise more challenging. One way to do this is to hold a weight plate or a dumbbell across your chest as you do each rep. Start with a low weight and gradually increase the weight over time, just as you use progressive overload when you train other muscles. Another approach to increase the challenge without doing high reps is to do ab crunches on a decline bench. Your upper body will have further to travel when you crunch and this will force the muscles to work harder.

What about Stability Abdominal Exercises?

You can challenge your abs more with stability exercises, like planks in several ways. One is to simply hold the plank position longer. However, once you can hold a plank for 60 seconds, try some harder plank variations. How about bird dog planks, Chaturanga planks, or walking planks to add more challenge?  Don’t forget about your obliques. Side planks hit the obliques, but you can challenge yourself more by doing a side plank with a leg raise, rotating side planks, or side planks with a crunch. There are tons of plank variations to choose from. So, don’t let your ab routine become boring or ineffective by doing only standard planks.

Abdominal Exercises Aren’t Enough

If your goal is to get ab definition, low rep abdominal exercises against resistance will hypertrophy the muscles, but you have to unveil those firm ab muscles and that means reducing your body fat content enough for them to show. Most experts say you need to get a little below 20% body fat for abdominal definition to show. Otherwise, those fit and firm ab muscles are cloaked in a layer of fat. So, a total ab workout involves more than just ab, core, and back exercises. Even the best of these exercises won’t burn a lot of fat. That’s where cardio comes in. This doesn’t mean you have to do 40 or 50 minutes of repetitive cardio, like jogging or cycling. High-intensity interval training is also a fat burner and takes less time. You can accomplish in a 20-minute session what it might take 40 minutes to achieve with moderate-intensity cardio. And, don’t forget about working large muscles groups with compound exercises, like deadlifts and squats. These exercises work your core too and because you’re using multiple, large muscle groups, they’re good for burning fat.

The Bottom Line

So, ditch the mentality that you have to do hundreds of crunches or hundreds of any exercise to get defined abs. Focus on adding resistance or keeping your ab muscles under tension longer by slowing down the tempo at which you do crunches. Finally, don’t depend too much on abdominal exercises to give you a six-pack, you have to get your body fat down as well.



Anders, Mark. “New Study Puts the Crunch on Abdominal Exercises.” ACE Fitness Matters Magazine, 5/14/2001.
ACE Fitness. “American Council on Exercise (ACE)-sponsored Study Reveals Best and Worst Abdominal Exercises”


Related Articles:

Are Planks Better Than Crunches for Abdominal Development?

Ab Training: Can the Quest to Get Defined Abdominals Lead to Back Pain?

Abdominal Training: How Often Should You Train Your Abs?

5 Ways to Make Planks Harder

Are You Making These 4 Abdominal Crunch Mistakes?


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