What is the Core?
What is commonly referred to as your abdomen, core, trunk, or mid-section is a regularly stressed focal point in the world of fitness and health. Many people think about their “six-pack” when it comes to their core, however, these are only the muscles on the front of your core while there are other muscles that wrap around your trunk in a 360-degree circle.
The transverse abdominis muscle fibers run horizontally from your front and wrap around your sides to your back while a set of oblique muscles run, you guessed it, obliquely around your sides as well. Your back muscles surrounding your spine are also part of your core.
All of these muscles combine to form a cylinder similar to those belts that you see people wear while squatting especially heavy at the gym. There are a couple of other muscles that form the top (diaphragm) and bottom (pelvic diaphragm) of the core. The top muscle separates your lungs from your abdomen while the bottom muscles form a sling that's your pelvic floor.
Abdominal Bracing vs Hollowing?
There are two schools of thought when it comes to using your core. Abdominal hollowing is when one draws in the front muscles of the core, activating the side muscles (transverse abdominis and oblique muscles). Abdominal bracing is the contraction of ALL the core muscles forming a "brace" around the entire trunk.
Both of these techniques stabilize your trunk, but do so in different ways. What's the difference and why does it matter? Read on to find out.
Why Does Core Stability Matter?
Before we dive into different methods of core activation let's first discuss why and where core stability matters.
It is thought that some areas of your body are designed to be more mobile (move more) while other areas of the body are supposed to be more stable (move less). Your low back and core is an area that is designed to be more stable while the surrounding areas (mid-back and hips) are supposed to be mobile. It is also thought that your brain is wanting to achieve stability in your low back since this leads to better biomechanics as well as protecting your spine and spinal cord especially during strenuous activity and exercise.
A poorly functioning core is often correlated with low back pain as poor stability in the low back can lead to aberrant motion in the spinal structures. This is why core strengthening has been a key in many low back pain rehabilitation protocols for more than two decades.
But core stability can also lead to better strength and performance in sport. One study in 2016 looked at the effect of abdominal bracing. The authors found that the training program significantly increased isometric trunk extension and hip extension strength, intra-abdominal pressure, and maximal lifting power (Tayashiki et. al., 2016).
By having a properly stable trunk, the task of transferring force from the lower limbs through the trunk becomes easier during movements such as a squat. Check out this article on how to improve your squat (hint: your core is a vital part of the equation).
If the core, which is primarily how stability is supposed to be achieved in the trunk, is not functioning to its best ability, it is believed that the brain will recruit other muscles (low back muscles, glutes, and hamstrings) to achieve this stability. This over-recruitment, however, is not necessarily good as there will be occasional instances where mobility is required in the low back and hamstrings, and if you don't have it, it may make you more susceptible to throwing out your back as well (check out the article about that).
This is a good reason to see a healthcare provider such as me, your Kirkland chiropractor who specializes in improving mobility, stability, and helping you gain the control to go between both.
Comparison of Hollowing and Bracing: What does the research say?
Let's first look at abdominal hollowing. A study in 2016 found that expiration combined with core contraction (hollowing) did promote spinal stability (Ishida et. al.). Hollowing has been long taught in some areas of sport and for good reason; it does improve some spinal stability. But the same study also found that it performed similarly to bracing. This sentiment is also found in another study (Kahlaee et. al.) where the authors found that abdominal hollowing made no difference in core muscle activity levels in those with chronic low back pain, whereas it was able to help reduce spinal extensor activity in pain-free controls.
But is it the best option to create stability?
A study in 2007 looked at the differences in lumbar compression and stability between hollowing and bracing. The best method would result in the most stability while having the least amount of compression which leads to a healthier and safer back. They found the amount of compression did not differ significantly, however, the amount of stability with bracing as opposed to hollowing was 32% greater (Grenier & McGill).
Another study in 2014 concluded, "Performing bracing exercises rather than hollowing exercises is more effective for activating the abdominal muscles." (Koh et. al.).
Does that mean that hollowing is completely no good? Not completely. My friend, Bellevue personal trainer, Hammad Haqqani states:
"Some clients are so dominant in their low back muscles that it's hard to teach them bracing or even to get them to do a plank without using a lot of their low back extensors and hurting. Hollowing can often be easier to teach which helps them gain stability in the core which is better than none when starting out a training program." That is a good point, but we both agree that bracing is more ideal when lifting heavy weights.
Another good reason for bracing is that it helps increase intra-abdominal pressure.
Intra-Abdominal Pressure
Intra-abdominal pressure (IAP) is a key component of abdominal bracing. Like it sounds, it is the amount of pressure within our abdomen. When we contract all of our muscles in the core and brace, we increase IAP, which increases the amount of stability. This pressure acts like a cushion on the front of our lower spine, helping to keep it stable.
Watching this video is a good demonstration of how increased IAP has a great effect on the stability of your core.
The Coke can is a good representation of your core. As already mentioned, there is musculature that forms a cylinder around your entire trunk as well as muscles that form a “lid” and a “bottom” to the core.
When the Coke can is empty (decreased IAP) the hydraulic press can easily smash it at around 75 kg of pressure. When the Coke can is full (increased IAP) it takes 360 kg of pressure to crush it! If you're trying to transfer power from your legs to your arms in sport, a solid core will prevent power leaks and aberrant motion in the lumbar spine.
Another way to increase IAP is also how we breathe. Proper breathing involves using the diaphragm muscle to "belly breathe" instead of "chest breathe." When belly breathing properly, the diaphragm muscle contracts and moves downward. This acts as a plunger and draws air into the lungs while simultaneously compressing the space in the abdomen. Since the pressure in the abdomen is being increased, the belly expands outward when we breathe in.
One way to practice this breathing is simply laying on your back with one hand on your chest and one hand on your belly trying to keep your top hand still and to move your bottom hand up and down with your breath.
Proper Bracing Tips
Now comes the tough part, pairing the breathing and bracing together. First, here’s a couple of tips on contracting all of your core muscles:
Lay flat on your back with your knees up and your feet flat on the ground
Using your fingers, press into both sides of your side and front core muscles
Clear your throat or cough and you should feel the muscles around your whole core contract
Now that you have felt those muscles, practice contracting and relaxing those muscles voluntarily
Once you have that down, try to pair that with belly breathing. One should be able to contract all of their core muscles through the entire inhale and exhale still utilizing their belly breathing technique. This would technically be an eccentric contraction of the abdominal muscles during inhale and then a concentric contraction during exhale.
How Can I help?
Proper core bracing and activation is easier said than done. If you need help getting your core to activate correctly don't hesitate to contact or visit our office to experience the difference of a Kirkland chiropractor who is there to guide you on your journey to wellness.
Thanks for reading and happy bracing!
References
Koh, H. W., Cho, S. H., & Kim, C. Y. (2014). Comparison of the Effects of Hollowing and Bracing Exercises on Cross-sectional Areas of Abdominal Muscles in Middle-aged Women. Journal of physical therapy science, 26(2), 295–299.
Ishida H, Suehiro T, Kurozumi C, Watanabe S. Comparison between the effectiveness of expiration and abdominal bracing maneuvers in maintaining spinal stability following sudden trunk loading. Journal Of Electromyography And Kinesiology: Official Journal Of The International Society Of Electrophysiological Kinesiology. 2016;26:125-129.
Kahlaee AH, Ghamkhar L, Arab AM. Effect of the Abdominal Hollowing and Bracing Maneuvers on Activity Pattern of the Lumbopelvic Muscles During Prone Hip Extension in Subjects With or Without Chronic Low Back Pain: A Preliminary Study. Journal Of Manipulative And Physiological Therapeutics. 2017;40(2):106-117.
Tayashiki K, Maeo S, Usui S, Miyamoto N, Kanehisa H. Effect of abdominal bracing training on strength and power of trunk and lower limb muscles. European Journal Of Applied Physiology. 2016;116(9):1703-1713. d
Grenier, S. G., & McGill, S. M. (2007). Quantification of lumbar stability by using 2 different abdominal activation strategies. Archives of physical medicine and rehabilitation, 88(1), 54-62.