Abdominal Bracing and Hollowing
Abdominal bracing is simply tensing (contracting) the abs as if you are about to be hit in the stomach (you don't have to do this will full force). Bracing the abs will automatically pull in the stomach slightly, but abdominal bracing does not involve pulling in or pushing out the abs. Abdominal bracing activates all the layers of abdominal muscles along with muscles deep in the lower back.
Abdominal hollowing is drawing in the lower area of the stomach toward the spine. This activates the deep abs but requires very little activation of the superficial abs muscles.
Both abdominal bracing and hollowing are both used to increase spinal stiffness to help stabilize and protect the spine.
In a study that compared the effects of bracing and hollowing on spinal stiffness, it was shown that abdominal bracing is significantly more effective than drawing in the abs in increasing spinal stiffness (the study used people without lower back pain). Abdominal hollowing did significantly increase spinal stiffness over rest.
Bracing the abs feels more natural than abdominal hollowing and is usually done automatically before movements of the arms or legs, lifting, etc.
To compare the effects of bracing and hollowing, wrap your hands around your waist then brace your abs. Next, simply draw in your abdomen towards your spine. When you brace your abs you will feel your front, sides, and back firm up. Stand upright, brace your core and tilt torso forward from the hip joints then return to upright position, then try drawing your stomach in toward the spine and doing the same. You will probably find it is easier to keep your back firm when bracing.
Bracing the abs before lifting helps protect your lower back.
Benefits of Abdominal Hollowing
Though bracing increases spinal stiffness more so than hollowing, abdominal hollowing may have its benefits.
During movement of the arm or legs or bending forward from the hip joints, the core muscles work together to stabilize the spine The muscles usually automatically contract just before the movement begins or very shortly after. The deepest abdominal muscle (transversus abdominis) contracts first.
Some studies have shown that in people with lower back pain, the contraction of transversus abdominis (TVA) is delayed (this delay may be a cause or result of lower back pain). A delayed contraction of TVA may result in lack of spinal stability, which increases risk of back pain. Some physical therapists use abdominal hollowing to help restore normal functioning of the deep abs. Drawing in the abs towards the spine recruits the deep abs without much recruitment of the outer layers.
The deepest abdominal muscle (transversus abdominis) supports the internal organs as well as works with the rest of the core to stabilize the spine.Abdominal Hollowing Exercise: targets the TVA
Lie on Back, knees bent, feet flat on floor.
Place hand on lower abs.
Inhale slowly and deeply.
Slowly exhale, pulling your lowers abs inward and upward toward your spine.
Repeat 5 times.
You can also exercise the TVA while sitting, standing, or lying down, simply by pulling in your stomach and holding the contraction.
Bracing the Abs Exercise strengthens Abs - can be done standing, sitting, lying
Place your hands around your waists.
Tense your stomach as if you were about to be punched in it.
Increase the contraction so that you feel your sides stiffen.
Hold contraction for 10 seconds.
Repeat 5 times.
The Plank (shown on the back exercises page) is an excellent exercise for strengthening the TVA.
Bracing (or hollowing if recommended by your physical therapist) the abs increase the effectiveness of core strengthening/stability exercises. Go to Lower Back Exercises.
In summary, abdominal bracing and abdominal hollowing both increase spinal stiffness over rest but bracing has been shown to be significantly more effective than hollowing. Abdominal hollowing recruits the deep abs with little involvement of the superficial layers and may be useful for retraining the deep abs in some people who have had back pain.