CrossFit and functional fitness athletes have pretty amazing physiques. They are shredded nearly year-round and are crazy strong. On top of their huge arms, bulging quads and thick backs they also have huge midsections. The abs we commonly see on CrossFitters has become known as turtle shell abs. The name pays homage to the belly of turtles – and immediately draws my attention back to the physique of the Teenage Mutant Ninja Turtles.
What are Turtle Shell Abs?
Turtle shell abs are characterized by a large, protruding rectus abdominis (6-pack muscle). The 6-pack appears to be big and block. Some may even describe the abs as looking 3-D (which is odd because humans are 3-D, but somehow the description makes sense).
The overly-developed rectus abdominis is framed by large obliques. Oblique (over-)development creates a very “blocky” midsection. This creates the illusion of a straight line from the arm pits through the hips.
The blocky midsection is in direct contrast to the V-taper midsection that is associated with classic body building physiques.
Though classic body building loved the V-taper, I find the block-shaped midsection to be a more athletic physique.
In some instances, the term “turtle shell abs” has been used to describe an abnormally distended mid-section as shown below. However, I feel like these are two distinct things.
For that reason, we’ll be talking about the blocky midsection version of turtle shell abs – which I think is what comes to mind for most people
CrossFit Athletes with Turtle Shell Abs
It’s clear that something about CrossFit leads to having huge abs. Pretty much all elite CrossFit athletes have huge rectus abdominis and oblique muscles. This leads to thick midsections that look super athletic and capable of handling high loads.
Read More:
What Mat Fraser & Kristi Eramo say you need in your CrossFit home gym
The equipment you need if you want to do the CrossFit Open at home
Key CrossFit Ab and Core Building Equipment
| Equipment | Uses | Available on |
| ProsourceFit Ab Mat | Crunches, sit ups and leg raises | Amazon |
| Rogue Sandbags | Heavy carries, throws, back extensions | Rogue |
| JDDZ Sports Resistance Bands | Anti-rotation work and obliques | Amazon |
| SKLZ Slidez Glider Discs | Anti-Extension/flexion work, mountain climbers, pikes | Amazon |
| Rogue GH-1 Glute Ham Developer | Lower back/hip strength, GHD situps, back extensions, reverse hypers | Rogue |
I’ve also written about the essential equipment you should have in your CrossFit home gym, according to Mat Fraser and Kristi Eramo. We walk through what Mat and Kristi have and their thoughts on why you need some key pieces of equipment to do CrossFit at home. You can read that article here.
What Causes Turtle Shell Abs?
Genetics
I think it would be amiss if we discuss muscle development and an aesthetic without mentioning genetics.
It’s clear that our genetics will shape the way our bodies look, how much muscle mass we can add and where our muscles are most notable. It’s no different when we talk about how our torsos look.
Some people simply won’t have the ability to grow large rectus abdominis or oblique muscles. Others may have a wide rib cage and thin hips which makes it tough to get the thick midsection associated with turtle shell abs.
If you look at the CrossFit athletes above, they all have a solid 6-8 pack and thick obliques.
Annie Thorisdottir has the most defined obliques. They almost look like fingers or gills coming off her side. Chandler Smith on the other hand doesn’t have huge obliques but has outrageous ab development.
Dan Bailey and Katrin Davidsdottir have a more balanced development of their midline.
Overall though, we can expect that the variation shown is at least in part due to differences in their genetics.
Luckily, a little bit of hard work can usually have an impact on the outcome of our genetics – whether you want to build turtle shell abs or have them and want to get rid of them.
Increased Trunk Muscle Size
It’s kind of obvious but those that have big, blocky abs and obliques have to put in serious work to develop them.
I think people often forget that the muscles of the core are, in fact, muscles. They need to be worked the same way that muscles of the legs or arms do. A progressive training program that involves endurance, hypertrophy, strength and power training is necessary for complete development of the core.
Check out my article here if you’re looking for ways to implement progressive overload to your training.
You have to focus on abdominal hypertrophy in particular to develop turtle shell abs. Straight up, the muscles need to be an adequate size to be visible and fill out the region.
If you look at your “normal” lean guy at a gym their midsection looks significantly different than those that do high volume core work mixed with heavy lifting and carries.
High Volume Core Work + Heavy Lifting
The best way to develop a thick midsection – and by extension: a protected spine, strong back and athletic torso – is via a combination of high-volume core work and heavy strength work.
This combination is why we see Crossfitters with the thick midsections shown above. But you don’t need to be a CrossFit athlete to reap the rewards of this combination of training types.
No doubt, you need to do isolation exercises that target the key muscles of the core. This means reps of leg raises, side planks, front planks, V sit-ups and hanging leg raises. If you want to go full CrossFit and mix in some GHD sit ups then all the power to you (but make sure you’re doing them right so you don’t blow up your back).
On top of that you need to do some serious strength training to get a thick midsection.
A recent study from Norway showed that the activation of the rectus abdominis increases as you perform more back squats repetitions up to 6 reps (van den Tillaar & Saeterbakken, 2018). This is right in the strength training rep range, suggesting strength work will impact the abs.
A review article in the Journal of Strength and Conditioning Research determined that squatting moderate loads is a better way to activate the trunk stabilizers when compared to instability core exercises (Clark et al., 2012).
CrossFit athletes are crazy strong. The best of the best will back squat up to 550 lbs (men) and 370 lbs (women). Here is a full breakdown of how strong the athletes at the 2022 CrossFit Games were.
Click here to learn more about the right sets and reps to achieve your goals.
Anterior Pelvic Tilt + Overdeveloped Erectors
Bad posture can lead to the appearance of turtle shell abs.
Over-developed spinal erectors, tight hip flexors and quads and anterior pelvic tilt cause the abdomen to protrude.
Strong and tight erectors will effectively shorten the distance between the base of the spine and the middle of the spine – basically pulling the back of the pelvis up. This leads the natural arch in the lumbar spine to be exaggerated.
Further, tight anterior thighs and hip flexors pull the front of the pelvis down.
This posture results in an anteriorly rotated pelvis. As a result, the abs seem to stick out and the butt appears raised.
I find this reasoning to be more apparent in female strength athletes. I’m not sure why it’s like that but that’s my observation.
Drug Use
A Google image search of “turtle shell abs” will bring up the below photo of a couple of bodybuilders.
In my opinion, this is something completely different. It seems to me that this distended abdomen look is a result of drug use.
(Though, I’m not suggesting that anyone that looks like this definitely did drugs).
Human growth hormone (HGH) is a performance enhancing drug used in strength sports to increase strength and muscle size. HGH is developed naturally in a gland deep within the brain.
It is produced for normal growth and development, and in response to exercise – strength training in particular. About 75% of natural HGH is secreted when you’re sleeping (Source). Which is part of the reason that sleep is one of the keys to recovery.
If you’re looking for more recovery tips check out my article on recovery tools and post-workout nutrition.
Taking HGH as a performance enhancing drug can lead to muscle and bone growth (Source). It may also lead to increased organ size. HGH can also cause swelling and fluid build-up.
I believe the picture of the bodybuilders above highlights the increased organ size, fluid build-up and swelling that are associated with HGH use.
The Takeaways
At the end of the day, you need to put in the work if you want a thick midsection. In my opinion, turtle shell abs are a great aesthetic – they make you look strong, shredded and athletic.
Performing high volume trunk focused (obliques and rectus abdominis) training coupled with HEAVY strength training is the key to getting thick, turtle shell abs. Following, functional fitness training methodologies should get you well on your way.
Happy lifting.