While you can’t solely isolate your lower abs, you CAN preferentially recruit the fibers of your lower rectus abdominis. You’re best doing this with exercises that involve raising your knees towards you chest, such as knee tucks, leg raises and pikes.
While these lower abs exercises involve hip flexion, you also need to remember that your abs aren’t hip flexors. You’ve got to get that “cock-up” if you want to effectively recruit those lower fibers – posteriorly tilting your pelvis at the top portion of these exercises are arguably THE goal of the exercise.
Meaty hip flexors can look good, but if you’re looking to work your lower abs more effectively then here are six moves you can try.
#1 – Incline Leg Raise in Rack
Try these in a smith machine or rack. These allow you to work more in the top position where the pelvic tilt is emphasised, and less in the bottom position where it’s largely an exercise for your hip flexors. You could do this on a flat bench but it wouldn’t be anywhere near as effective to recruit your lower abdominals.
If you were to do this on the flat the load would actually be reduced at the top as your pelvis posteriorly tilts. Making it pretty useless. By placing you on a decline you’re able to maintain load and tension at the top of the exercise. It also helps emphasise an elongated eccentric contraction.
- Set your bench on to an incline. The higher the incline the harder it’ll be.
- The seat should be flat so as to act as a stopper for going too low.
- Set the bar in the rack or smith machine to enable you to hold at full arms length when laying on the bench. Note: when using the rack the bar should be on the inside of the rack on the hooks, and you should be on the outside to stop the bar falling off.
- Lock yourself in to position holding tightly on the bar and using it to help engage your lats (imagine a straight arm pull-down or pullover).
- Using either a straight-leg raise or knee raise, lift your knees towards your chest.
- Come as high as you can before lowering down under control.
- Rinse and repeat.
#2 – Knee Raise on Hack Squat
Like the previous move this is another frequently forgotten lower abs exercise. I remember reading about these in about 2006, and I think the article was from the 90’s! Strange how often things in fitness come full-circle. Well I’m helping these make a comeback because they’re a great use of the hack squat outside of leg day – and we know how infrequently that comes around for some!
The natural angle of the hack squat makes this an ideal set-up for knee raises. These are much harder than they look. Since range of motion at the bottom is limited anyway, spending more time at the top of the knee raise is a given.
- Lock yourself in to the hack squat using the shoulder pads and handles.
- Bend your knees and let the handles take your weight.
- Raise your knees towards your chest as high as possible.
- You can do these with a slight tap on the floor (without using it to cheat) or like in the video without floor contact.
#3 – Hamstring-Activated Reverse crunch
By activating your hamstrings (and glutes) you reciprocally inhibit your hip flexors. You’ll not shut them off completely, but just enough to stop them taking over in common abs exercises. This is especially important during exercises where your lower abs are being targeted.
By crushing a foam roller in that sweaty gap between your calves and hamstrings, you’ll make reverse crunches a whole lot harder. Do these on a flat to get used to the feeling, then use a decline bench to help further load the top position.
- Crush the foam roller with your hamstrings. If the foam roller slips then try wrapping it in a towel or sweater.
- Hold on to something for stability, like a plate, kettlebell, or disused exercise machine.
- Lift your feet off the floor focusing on lifting your hips off the floor at the top – tilt your pelvis.
- Exhale fully at the top of the movement to contract your abs fully.
#4 – Swiss Ball Knee Tuck to Roll-Out
In THIS study Escamilla et al. (2010) tested 8 abdominal exercises using the Swiss ball. From the conclusion: “The roll-out and pike were the most effective exercises in activating upper and lower rectus abdominis, external and internal obliques, and latissimus dorsi muscles, while minimizing lumbar paraspinals and rectus femoris activity.” The knee tucks weren’t too far behind the pikes either.
Combining these two exercises together is a double-whammy for your overall abs development. I like starting out with the SB roll-out to knee tuck, before progressing on to the SB roll-out to pike (providing your hamstrings will allow it!!). Props to Coach Nick Tumminello for the original idea.
- Make sure you can do both knee raises and full body roll-outs on a Swiss ball first before trying these. It only makes sense since you’re adding both together here.
- Place your hands on the floor then gracefully put your shins on the Swiss ball. You’ll find there’s a bit of a sweet spot for this one.
- Make sure you’re well-balanced before pulling your knees up towards your chest. Return back to the start.
- Follow-up by pushing your hands in to the floor to slide your body back on the ball. The ball will travel up your shins and thighs.
- That’s one full repetition.
#5 – Hamstring-Activated Roll-Out
Although technically these aren’t a “lower” abs exercise, they’re pretty much top of the podium for overall abs development. As if basic ab wheel roll-outs aren’t hard enough, try this hamstring-activated version.
Squeezing a medicine ball in the way shown in the video will activate your hamstrings, and just like the hamstring-activated reverse crunches will help inhibit your hip flexors. The weight of the ball this will also load the bottom position of the roll-out somewhat. If you think roll-outs are a challenge then this is a whole other beast.
- Set yourself up to perform basic roll-outs. Now get ready to step it up…
- Place a medicine ball between your heels and butt, crushing the ball by using your hamstrings.
- Squeeze your butt – imagine trying to crack a walnut between your cheeks.
- Lower yourself down bracing hard in the bottom position. You’ll find it harder to resist spinal extension here. But that’s sort of the point.
- Return back to the start position, pulling your ribs to your pelvis at the top. And don’t give me any of that “spinal flexion is bad” crap.
- That’s one rep. Good luck trying to hit double-digits with this one!
#6 – Smith Rack knee Raise
Your lower abs work to posteriorly tilt your pelvis at the top of these exercises. For example when your knees raise higher than your hip crease in knee raises, or butt comes off the floor during a reverse crunch.
To work your lower abs it’s important to find exercises that allow you to work more in this position. In essence the set-up and your strength levels permit loading this range of motion. Here’s a set-up I like using a smith machine for.
Anecdotally I find most can get greater range of motion here in the top position compared to, for example, hanging knee raises or using a captains chair.
- Set the bar to just above shoulder height.
- Use a barbell pad on the bar for comfort.
- Hook your arms over the padded bar, creating as much stability as possible. Crossing your arms can help.
- Without swinging, raise your knees towards your chest using your elbows as the stopping point. If you can’t work this top range of motion then you won’t be using this exercise to its full effectiveness. Regress to something a little easier if need-be.
There’s nothing special about your abs. Just like any other muscle made of the same thing, they require progressive overload in order to develop. I tend to suggest 8-15 reps for all abdominal training, with the odd foray in to the 20-30 repetition range every once in a while. Set your target rep range, then once you can hit those reps comfortably you can either add weight or add more reps. Feel free to add complexity too, but not at the expense of maximal muscle tension.
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