The lower abdominal area is a common area of concern for many which leads to many questions for me as the personal trainer! The most common question I get is “What exercises should I do to define my lower abs?”. What I gather from this question is my client is also asking me “What exercises activate the lower abs?”
This question has been quite the debate among fitness experts and enthusiasts alike for quite some time. In this article I will tell you what the research has to say!
This is what we do know for fact however:
- You can’t “isolate” the lower abs . . . or even the upper abs! What I mean is you can’t completely shut one off and isolate the other.
- Aesthetically, body fat percentage trumps all core exercise you do. If your body fat is too high, your abs will never show; especially the lower abs which is where most people lose fat last.
- If your body fat levels are low enough to have clear cut core definition, your lower abs “muscle gains” from doing exercises that may preferentially target the lower abs likely would be minute.
These three things are foundationally most important and will trump everything else within this article. Don’t leave yet though, if you combine these three things with what research has to say, then you may be on your way to outstanding lower ab definition!
Anatomy of the Rectus Abdominis
When most people talk about building their abs, they are talking about their rectus abdominis muscle whether they know it or not!
The rectus abdominis is the superficial “six pack abs” muscle we all deeply covet. Generally, it stretches from the pubic bone, and stops at the sternum.
Research on Preferentially Activating the Lower Abs
There are actually quite a few studies showing that you can preferentially engage the lower abs versus the upper abs depending on your exercise choice.
What they have found is generally, exercises with a posterior pelvic tilt (think opposite of low back arch) provide better lower abs activation when compared to exercises such as a sit up or curl up which provide better upper abs activation.
On the other hand though, one well known study by Dr. Stuart McGill found conflicting evidence, saying that you can’t preferentially activate the lower abs or upper abs. According to Dr. Stuart McGill, there were issues with normalization in previous studies stating:
“ Without normalization (ie, expressing the EMG signal as a percentage of the maximum activity that muscle can generate), different muscles can not be quantitatively compared. For example, concluding that the lower abdominals have less EMG activity than the upper abdominals when the signals are not normalized may not be due to the ability to preferentially recruit.”
In his study though, he did find very small differences in upper rectus abdominis activation versus lower rectus abdominis activation. The difference was so small though that there was no practical value to clinical use.
In a separate study conducted by Bret Contreras, he found that you can preferentially activate the lower abs versus the upper abs. He also made sure to normalize his EMG data.
Further, Bret Contreras also made a comment about Dr. McGill’s criticisms on previous studies saying:
“I know some professors who are adamant that he’s incorrect on the matter.”.
The Verdict on Engaging the Lower Abs
As stated earlier in this article, this isn’t a simple yes or no answer. Overall though, the answer seems to be leaning towards yes, you can preferentially engage the lower abs versus the upper abs with the right exercise selection and some practice.
Exercises with a posterior pelvic tilt provide better lower ab activation when compared to exercises such as a sit up or curl up which provide better upper ab activation.
Examples of a few ab exercises that will preferentially engage the lower abs are leg raise exercises or reverse crunches and its variations.
Exercises to Engage the Lower Abs
Reverse Crunches
Reverse crunches are a great exercise to engage the lower abs because of the posterior pelvic tilt added when done properly!
To do reverse crunches, lay on your back with your hands behind your head and legs up, bent at a 90 degree angle at the knees. From here, curl up bringing your knees and head towards each other, and then return back down to complete one rep. Three sets of anywhere from 10-15 reps is a great starting place!
Seated Leg Raises
Next up are seated leg raises. This variation of leg raises is a good starting place in terms of the challenge and ability to learn proper form for lower ab activation.
Start seated at the edge of a chair with your legs extended. From here, bring your knees towards your chest, hold for a brief pause, and return to the starting position. Three sets of anywhere from 10-15 reps is a good starting place for the seated leg raise.
Importance of Exercise Selection to Activate the Lower Abs
Before wrapping this article up I do feel it’s important to specify that spinal flexion exercises are the best choice for building the rectus abdominis.
Spinal flexion is the anatomical name for forward bending. Therefore, think exercises like crunches, leg raises, bicycle crunches, etc., when thinking about building “six pack abs”.
Exercises that would not be good for building six pack abs would be planks, side planks, shoulder taps, etc.
This doesn’t mean you shouldn’t do these exercises however! Core exercises involving an isometric hold are very important to building core strength and stability. This opens up room for an entirely new conversation though that I won’t cover here!
Have you had trouble with your lower ab definition? Did exercises that preferentially activate the lower abs help?
Sources:
1.) McGill, SM & Lehman, GJ 2001, Quantification of the Differences in Electromyographic Activity Magnitude Between the Upper and Lower Portions of the Rectus Abdominis Muscle During Selected Trunk Exercises, Viewed 28 September 2020, <https://academic.oup.com/ptj/article/81/5/1096/2857594>
2.) Contreras, Bret. “ABC (Ask Bret Contreras) – Is It Possible To Isolate The Upper Or Lower Abs?.” bretcontreras, Bret Contreras, 18 November 2010, https://bretcontreras.com/abc-ask-bret-contreras-is-it-possible-to-isolate-the-upper-o-lower-abs/.
