Transversus Abdominus (TrA) is not just one big muscle,
TrA is made up of 6 separate parts. Upper/Middle/Lower and left & right sides. Different portions of TrA will activate to help stabilise under a rotational load, for example when walking - with trunk rotation. (Allison, GT et al. 2008). If I twist my knees to the right side in a supine position, my right lower TrA will activate and upper and middle left portions will activate and the opposite will happen if the knees twist to the left. Therefore, both sides of TrA should not be activating equally with functional arm and leg movements. When training TrA we should be thinking that due to the rotational activation of the TrA muscle it is important to include alternating leg or arm movements with training of core muscles. This will ensure that a small amount of trunk rotation will occur to help automatically activate the TrA muscle.
It is recommended to begin performing "core" exercises in a position where the body feels comfortable and happy. Neutral spine to perform TrA activations is NOT necessarily the case. The spine should be in a position where you feel as though you can
move without pain and with good control. In some people this may be in prone elbow prop (cobra) position or supine lying with 2 pillows under the head and shoulders. Everyone has a slightly different shaped spine and perform different postures during the day, so why should everyone be set up in the same neutral spine position?
The article referenced below by (Morris, S., Lay, B., Allison G.T. 2012) concludes there is
no justification of training bilateral pre-activation of TrA before movement of the arms and legs. It creates a rigid system which is considered dysfunctional (something which pilates instructors, including me, have been teaching for the past 20 years). It encourages gripping of internal & external obliques and doesn't necessarily activate the TrA. In addition, this gripping can put pressure on the pelvic floor muscles and reduce the basal excursion of the rib cage in diaphragmatic breathing. Which clinically relates to using static planking as an exercise for core strengthening...is it really a good way to train our core?
Another little known fact is that when the legs or arms are put under a small amount of resistance (ie: placing a foot in a resistance band to move against when doing leg slides), it is easier to recruit your TrA muscle than when performing supine core work with legs in the air. Supine core work as an open chain leg exercise is not under load and therefore not a good recruiter of TrA muscle - this once was thought to be a beginner exercise, however, it is now considered a more complicated and advanced position to active TrA. One way to help encourage TrA is by adding some feedback or semi-closed chain/resistance to leg and arm movements, it encourages the core system to be activated without conscious control.
Performing repeated movements (2 x 30 reps) with some light resistance bands as you continue with the movements is ideal for TrA activation (tradition thought was sets of 6-8 reps). TrA exercises should feel as though it is getting easier to complete the task as you continue to do the exercise rather than fatiguing. This may be due to the background stability and neural control of the body improving or activating with more repetitive movements in a comfortable posture.
As an instructor, always watch the shape of the abdominal wall to give you an indication of which muscles are working during activities. Some different shapes of the abdominal wall you may see include:
The Rectus Abdominus dominant muscle will cause a "doming" of the abdominal wall.
If External & Internal obliques are dominant they will cause a "gripping" effect on the rib cage and reduce lateral basal excursion of the ribcage with breathing. There may be lines appearing down both sides of the abdominal wall and a line may appear horizontally just superior to the umbilicus.
If TrA is activating and the more external muscles are relaxed then you will notice a flattening effect mainly from the lower half of the abdominal wall, whilst being able to keep the upper body relaxed and breathe using the diaphragm.
Educating
your clients to focus on particular muscles with each exercise. Eg: show your client a picture of the muscle and explain its function so they understand why it is important to activate.
Placing a hand on the external obliques muscles
This will help the body relax or downtrain the gripping and dominance of the external obliques, allow the client to feel any lateral basal breathing movement and help TrA activate.
Lower thoracic spine rotation stretch
Always think about where the nerves originate before trying to strengthen a particular muscle. The nerves from lower thoracic spine supply the TrA muscle. Exercises like book openings, sit twists and thread the needle encourage breathing and "downtraining" of obliques and help to open up the pathways the thoracic nerves will take on their course to the TrA muscle.
Make sure the client is not in pain
Remember that neutral spine is not always a "happy place" to begin core exercises. Always check if you client feels stronger in prone or supine or sitting or standing postures before starting core work. Some clients will prefer more spinal extension core exercises (eg: cobras) and others will prefer some spinal flexion based core exercises (eg: roll ups).
Stretch out Hip Flexor muscles
Hip Flexor dominance and low back pain tend to be a common problem. It may be difficult for your client to activate core if their hip flexor muscles are gripping on. I often find clinically that a good stretch out of the hip flexors can help to reduce the muscle tension and allow the core muscles to activate.
Activate your pelvic floor muscles and don't think about your TrA muscle or abdominal contractions. The fascial connections of pubococcygeus and TrA have shown to facilitate activation. So if you think about slowing down the flow of urine or lifting up testicles (boys) or lifting up through vagina (girls) it can help kick start a contraction of the TrA muscles and the whole inner core unit.
Repetitive movements of arms and legs
Alternate movement of arms and legs is another solution! No more planking holds or side support holds until your poor client is shaking. We need to bring in alternate arm and leg movements to keep the alternating pattern of TrA activation in addition to reducing the over contraction of the oblique & rectus abdominus muscles to help encourage strengthening of the core muscles.
Keep breathing - do not hold breath and do not forcefully exhale
BREATHE! If you grip on and hold your breath you will definitely be focusing on recruiting the outer abdominal muscles and not necessarily training your TrA muscle. The excessive increase in IAP with the Valsalva Technique has shown to increase strain on the pelvic floor and cause excessive tension in the external obliques and rectus abdominus muscle.
I hope this has helped shed a light on the new trends in activating and strengthening the Transversus Abdominus and core muscles. Remember if you have any feedback or questions about exercise rehabilitation that you would love answered, please write to us or click here:
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References:
- Allison GT et al (2008) Feedforward Responses To Transversus Abdominus Are Directionally Specific and Act ASymmetrically: Implications for Core Stability Theories JOSPT, May 2008 vol 38,5
- Morris S, Lay B and Allison GT (2012) Corset hypothesis rebutted - Transversus abdominus does not co-contract in unison prior to rapid arm movements Clinibiomech. Vol27. 3 p249-254
