Fitness and strength coaches use the term abdominal bracing to describe a very specific way of contracting the core musculature to provide adequate levels of stiffness and stability to the spine during lifts performed in a gym.
Several exercise disciplines use the term abdominal brace in a number of ways and via the use of different muscles to achieve outcomes specific to their activities. For example, in Pilates, the way the abdominals are contracted are different to how a gymnastics coach would encourage the core to be used by the athlete.
The various ways of engaging the core should be viewed through the lens of what the outcome is – what level of stability is required for the activity? Most of the confusions that exist in the fitness industry has to do with the specific ways of teaching core control - which might be entirely appropriate in one setting, such as rehabilitation or Pilates, but may not provide the support and core control encountered and required during heavy resistance training exercises, such as squats and deadlifts.
When we understand that different modes of exercise have different spinal loading demands and patterns of use, we realized that the controversy is that exist in the fitness industry are often because we're trying to use one way of engaging the core in a different situation, where it may no longer be a sufficient type of core control.
During resistance training, certain movements place a very high demands on spine control. Some of these loads are compressive, some are shearing, and some are rotary. Depending on the demands of the specific exercise, various groups of muscles will be up or downplayed (with the exception of the quadratic lumborum, which seems to be highly active in all challenges to the spine).
A number of abdominal bracing techniques have been studied in the scientific literature, both using computational models of spine stability, porcine spines (which serve as nice models of the human spine) and also electrical measurements of muscle activity in the trunk.
Spine stability appears to be enhanced by adopting an abdominal brace, which sees all the muscles of the trunk engaged, without external change to the circumference of the abdomen -not pushing out, not drawing in, simply tightening and flexing the core musculature. The best way to think about this is as if you are preparing to be punched in the stomach, so you tighten up the front, side and back muscles that comprise the core.
Studies investigating this specific way of bracing the abdomen show very high levels of spine stability for exercises that impose high compressive, shear and rotary forces to the spine. By adopting an abdominal brace and keeping the spine in its neutral curvature, we see that the spine has its highest level of protection against sustaining an injury.
The next step is to engage the core muscles in this manner while maintaining continuous breathing, such that the abdominal recruitment occurs at an unconscious level.
Performing front planks, side planks and bird dogs while maintaining constant tension in the abdominals and a normal breathing cycle are all recommended ways of training the abdominal brace to become unconscious.
The two final considerations are how hard do we tense the muscle and should we hold our breath while lifting.
Firstly, the level of recruitment of the abdominal muscles during bracing. The level of tension used when creating an abdominal brace during lifting should not be maximal. It has even been proposed to be around 70% of maximum, so it's a moderate to hard tensing of the abdominal musculature, but not so maximal that it causes you to hold your breath and prevent any movement whatsoever.
Secondly, the use of breath holding has been used in weightlifting for many decades. This is known as a Valsalva maneuver, where you exert force against the closed throat (known in gym circles as the ‘breath that never happened’). The reason for adopting a Valsalva maneuver during resistance training is to increase intra-abdominal pressure and generate high levels of support for the spine. If you are performing a 1 repetition maximum lift, then a Valsalva maneuver can be adopted. For everyone else, it is recommended to use a constant breathing cycle or exhaling through pursed lips on the concentric and inhaling through the nose on the eccentric. This is a wiser approach, as it better maintains blood flow to the brain and normalizes blood pressure.
There has been a lot of confusion about abdominal bracing and how to best perform this in the gym. The purpose of an abdominal brace is to recruit the core musculature in such a way that it provides support for the spine in all the various ways the spine can be challenged in the gym, through all the diverse and various exercise movement patterns.
The version of the abdominal brace that research supports as providing the highest degree of stability is where you tense all the muscles of the abdominal wall, like you are preparing to receive a punch to the abdomen - this recruits the anterior, lateral, posterior and all the deep core muscles to provide stability for every type of load challenge to the spine. Remember to breathe consistently throughout the movements or exhale through purse lips during the hardest lifting part and inhale through the nose during the lengthening portion.
Finally, other methods for core control used in other disciplines (such as drawing in to engage the deep core) are not recommended to be used in the weights room, where the imposition of loads to the spine are significantly higher than those encountered in rehab or Pilates settings.
Reference:
Grenier SG, McGill SM. Quantification of lumbar stability by using 2 different abdominal activation strategies. Arch Phys Med Rehabil. 2007 Jan;88(1):54-62. doi: 10.1016/j.apmr.2006.10.014. PMID: 17207676.
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