If you spend time on social media, you know plank challenges are all the rage.  Have you ever considered what exactly the plank does for the core?  You know it makes it stronger when you do it correctly, but planks also stabilize all the core muscles.  Core stability is important not only for a great looking mid-section, but also for hip mobility.  Via connective tissue, the diaphragm directly links into the psoas, pelvic floor, quadratus lumborum, obliques, and other muscles that influence hip mobility.

Each joint has either a stable or mobile functionality.  In the case of the core, it should provide stability because it keeps you upright all day.  Your hips, on the other hand, should be mobile in order for you to walk, run, squat on the toilet, etc.

Think of your core as an egg.  The top dome is your diaphragm.  The bottom (upside down) dome is your pelvic floor.  Those two domes need to sit precisely in alignment for the whole core to stabilize properly.  If the ribs move, the diaphragm changes position.  If the pelvis moves out of alignment, the pelvic floor changes it’s normal resting position.

Your core may be out of alignment without you realizing it.  A very common postural distortion called anterior pelvic tilt results in a weak, misaligned core (or badly shaped egg.)  Core stability is reduced when you are in an anterior pelvic tilt.  Notice in the anterior pelvic tilt that the lower back curve is increased, the pelvis tips forward, the belly bulges out, the ribs flare out, and the head juts forward to offset the weight shift when the center of gravity moves forward.

anterior pelvic tilt picture

Photo source: alexmedearis.com

In many cases, muscles will not allow range of motion because the brain is trying to protect the body.  The brain senses an instability and limits mobility to reduce the chances of injury.  If your core is unstable due to anterior pelvic tilt or other reason, your brain may respond by trying to get that extra stability from your hips and thereby stealing hip mobility.

Let’s look at an example.  In the picture below, you see my client performing a hip internal rotation assessment.  The before picture reveals limited internal rotation range of motion.

Internal rotation range of motionThe after picture was taken after simply doing a few side planks.  The side plank stabilized his core and allowed his hip to move more freely.

My colleague, Dean Somerset, explains this phenomenon well,
“The reduction in hip internal rotation is merely a symptom of something else not working properly. Because of this, we could stretch it as much as we like and never see any difference. As a result, we have a generation of people focused on the kinesiology of “stretch the tight” without asking the best question possible: why is it tight in the first place? Muscles don’t just get tight on their own, they’re told to be tight.

Stretching plays a role to help reduce neural drive to a muscle and overcome the protective mechanisms causing a muscle to be tense. However, it doesn’t address the cause of the muscle being tense in the first place.

If the muscle is tense because it’s protecting a perceived instability, compensating for another area of the body that isn’t generating enough tension to stabilize an area, or is guarding against a perceived threat, it will maintain tension until any or all of these 3 scenarios are remedied.

Because of this, a simple stabilizing movement such as a side plank can have a massive impetus to promote stability, co-contraction from multiple segments, and reduce the perceived threat to injury due to the up-regulation of other muscles that contribute to the motion.”

I had my client do a 10-second side plank, rest for 5 seconds, and repeat for a total of three reps.  These short intervals reduce core fatigue and allow for better alignment as opposed to a 30-second side plank.

Side Plank

By improving your core stability, you can improve range of motion and mobility in your hips.  Hooray!  Another reason to work on your core!  But seriously, crunches do not improve core stability.  It’s the exercises where your trunk/core has to be strong and hold it’s position, like planks, dead bugs, wall press abs, farmer’s carries, and Pallof Press.

So, there you have it!  Core stability improves hip mobility.  Watch this video on how to check yourself for anterior pelvic tilt and start correcting that posture because that will go a long way for improving your core stability.  Also, consider reducing the amount of stretching you’re doing for your hips and increasing the core stability exercises.