What Your Core Really Is
Four holds, two comparisons, and what the gap may tell you.
Ask someone to point to their core and most people point at their abs. That is only part of it. The core is in fact more than just that: it is the brace that supports all movement, and a breakdown at this point in the chain radiates everywhere. Over the years of working with and learning from great orthopaedic surgeons, DPTs and other coaches, I have learned how four holds and two comparisons can tell you where you stand, and what you should focus on and support.
Your Core Is Your Whole Trunk
Your core is your whole trunk, also known as the lumbo-pelvic-hip complex (LPHC): the muscles in front, the ones along your sides, the ones running up your spine, and your glutes and hips underneath. They work together like a brace. They help keep your spine steady, and they pass force from your legs to your arms when you lift, swing, or throw. A six-pack has very little to do with it.
Fun fact: according to NASM's corrective exercise textbook, the LPHC has between 29 and 35 muscles that attach to the lumbar spine or pelvis.
One way to picture it is a cylinder with four walls: the front, the back, and the right and left sides. The bottom is your pelvic floor, which is why proper form is important. Each plank in the test below loads one of the walls.
| Wall | The plank that works it, and what that wall does |
|---|---|
| Front | The front plank. The front wall is what keeps your low back from sagging when you stand, carry and lift all day. |
| Sides | The side plank. The side walls are your obliques plus the hip muscles that stop your pelvis dropping every time you take a step. |
| Back | The reverse plank. It loads the muscles either side of your spine along with your glutes, and opens the chest and shoulders while it does it. It also builds endurance in your posterior chain, the muscles along the back of your body that help you stand upright. |
A neutral pelvis acts as the floor. Think belly button to spine during the holds, and you will naturally pull yourself to neutral.
Why the Gaps Matter More Than the Times
So we are not testing how many crunches you can do. We are testing balance and endurance. This is adapted from Dr. Stuart McGill's core endurance tests, which many trainers and physical therapists use.
McGill and two colleagues timed four holds in 75 healthy young adults: a back hold off the end of a bench, a seated lean-back hold, and a side bridge on each side. They published the times and the ratios between them as targets for testing and training. The side bridge is our side plank. The front plank and the reverse plank are modified versions of his other two holds that you can do yourself, with no outside help or equipment. The idea is simple: the times matter, but the comparisons matter more.
Lower back pain and sitting for a long time can affect our body and give us misalignments that can lead to injuries down the line and keep us from moving. That is why you need a strong, stable core.
In one study of 100 university employees, the people who sat for more than half the workday held all four core endurance tests for less time than the people who did not.
One study links weak back endurance to back pain. A 1984 Danish study followed about 900 adults ages 30 to 60 for one year. Men whose back muscles held out longer on a back endurance test were less likely to have a first bout of low back trouble.
Both studies have limits, but they point the same way: longer holds went with less sitting in one, and with fewer first bouts of back trouble for men in the other.
I am a NASM Corrective Exercise Specialist. Whether in sport or just moving around in everyday life, as we age we feel the imbalances in our body add up and cause pain or injury. Keeping a strong and mobile core, especially the hips, is important to prevent those injuries and let us perform better and longer in our lives.
What an Orthopaedic Surgeon Told Me About the Core
I talked with Dr. Felix "Buddy" Savoie, Ray Haddad Professor and Chair of Orthopaedic Surgery at Tulane University.
While I was speaking with him for a future column on the mid back and shoulders, he started with balance and posture, which he called the key to shoulder stability, and went straight to core strength, the legs and the hips. He said a general fitness program is a good way to look after the shoulder.
Later in our talk, he came back to where we started:
"If the back of your shoulder is strong and your hips and core are strong, then you can protect your shoulder."
Dr. Felix "Buddy" SavoieRay Haddad Professor and Chair, Orthopaedic Surgery, Tulane University
Dr. Savoie's statement shows how problems in the core can radiate to other parts of the body.
The Four Holds and How the Test Works
The test is four holds: a front plank, a side plank on each side, and a reverse plank. Hold each one as long as you can and write down the time. Do them in this order. If you cannot do these from your feet, do them from your knees.
Front Plank
Forearms down, elbows under your shoulders. One line from heel to head, chin tucked. Squeeze your glutes, pull your ribs down and brace like you are about to take a punch. Eyes on the floor just ahead, not up. Belly button to spine.
Side Plank
Forearm down, elbow under your shoulder, feet stacked. Head in a straight line, chin tucked. Build the tension first, then lift the hips. Push the down shoulder away from your ear. Keep one line from ear to ankle. Belly button to spine. You hold this one on both sides, left then right.
Reverse Plank
Face up, legs straight, heels down. Hands under your shoulders. Point your fingers toward your feet or away from them, whichever feels better on your wrists and shoulders. Drive your hips to the ceiling and hold them there. Squeeze the glutes hard, open the chest, and do not let the hips sink. Belly button to spine.
When to stop: stop the clock when your hips drop, or when you come down.
Rest: one minute between holds. None after the last one.
The full walkthrough, with a calculator: How to Do Your Own Core Assessment.
This test is coming to Built & Balanced as one of its self-checks. It will walk you through it and do the math for you.
Coach's Note:
- Have a pen and paper with you. While you are resting, take note of what you felt and where.
- Why did you end the test? Was it your shoulders, obliques or hips that gave out first?
- Use this as a way to know your body better, and save the notes for your doctor, coach or physical therapist.
How to Read Your Two Comparisons
Your left side plank against your right side plank.
Aim: within about 5 percentYour front plank against your reverse plank.
Aim: reverse at least matches frontYour two sides. McGill's rule of thumb is that your left and right side planks come out within about 5 percent of each other. Read that as a direction, not a pass line: most healthy adults land further apart. In a 2022 study of 68 healthy adults, the typical person's right and left side holds matched, but the middle half of people ran from about 20 percent shorter to 20 percent longer on one side. So treat the 5 percent as a goal, not a pass or fail. Pain is the fail.
To figure your gap, divide the difference between your two sides by your longer side, then multiply by 100. If your left side held 62 seconds and your right side held 71, that is a 9-second gap, and 9 divided by 71, times 100, is 12.7 percent.
Front and back. Our coaching target is a reverse plank that at least matches your front plank, and then outlasts it. Long term, shoot for 1.5 times as long. Again, the front and reverse planks are modified versions of McGill's assessment. It is just a coaching target.
The two comparisons tell you where to start: your weaker side, or the back of your core. Retest after 4 weeks of consistent effort.
Before You Test
Answer three questions first:
- Has a doctor ever told you to avoid intense exercise?
- Do you get chest pain or unusual dizziness during activity?
- Any current injury this test could make worse?
Yes to any? Sit this one out for now and check with your doctor. This test will be here when you are cleared.
How to Take Your Test
- Do the four holds and write down each time. The walkthrough has a calculator: How to Do Your Own Core Assessment.
- Check your two comparisons: your two sides, then your front against your back.
- Put a retest date on the calendar, 4 weeks out.
Built & Balanced
If you want a plan to build on your numbers, Built & Balanced is my six-week program for busy adults and anyone getting back into training: four workouts a week, about an hour each, in the MaxWell Nutrition app. It comes with MaxWell Nutrition Unlimited.
Your core is your whole trunk: front, sides and back. Four holds and two comparisons show you where yours stands and where to start. The gap is the information. Fix the gap before you chase a longer time. Retest after 4 weeks of consistent effort, and you will have your numbers against your numbers.
Take your test: How to Do Your Own Core Assessment.
Spencer Maxwell Shilstone
Founder of MaxWell Nutrition and Shilstone Performance Systems. Spencer works with teams and individuals to help them reach their performance goals. He has the honor and privilege of working with and building integrative performance programs for members of U.S. Army Special Operations Command. Optimum Performance is his column at MaxWell Nutrition.
