Speaking of the dead bug maybe you'll get into this later but I've seen some prescribe a posterior tilt and lower back sucked into the floor with no space (Robertson, Cressey) but have also seen a more nuetral spine more recently being advocated to emphasize TVA involvement.
Well now you know why this takes me so long! Do I write pages of explanation to try to eliminate all the confusion and in the end simply create more confusion? Or do I say..here's how to do it and here's a brief explanation as to why.
Combining the two things, McGill and the issue of planting the back or just using a neutral I can create all sorts of confusion right now. First of all when McGill talks about the issue of abdominal hollowing what he is trying to do is counter the myth that the transverse abdominus and multifidinus are the "keys" to spinal stability and you can use abdominal hollowing to activate them thus creating a more stable spine during heavy lifting or athletic activities (two COMPLETELY different things, really). He is countering "CHEK" and the "Australians" who preach that stuff. He says (and so do I) you want to use abdominal bracing but abdominal bracing is NOT the same as abdominal hollowing and you need ALL the muscles and you want to INCREASE the distance between the "hoops" of the abdomen not decrease it. So what he means is you don't go around lifting heavy weights or playing football with your gut sucked in. Unless you want to look like a supreme douche like Paul Check weezing your way through a workout (you can't BREATHE properly with you gut sucked in…it inverts your breathing).
Okay so what about "isolating" the TVA (and MF). Yes, many believe some people can preferentially activate it, etc…McGill says he saw no evidence of this. But he doesn't say that abdominal hollowing doesn't contract the TVA because of course it does. The question therefore is can you do that in a way that doesn't use any superficial muscle activity.
For instance, some sources say, during these spinal stabilization tracks, that you must learn to do abdominal hollowing using the TVA, multifidinus and "deep pelvic floor" muscles preferentially and to do that during the dead bug for instance you would place some fingers about an inch medially and inferior to the superior iliac spine and attempt to palpate the TVA and do kegel like contractions to feel it as opposed to using action of the superficial musculature of like the RA and obliques.
As an example, in Conservative Management of Sports Injuries, the author instructs, after getting in the hook lying position and palpating the TVA:
Instruct the athlete to take a deep breath in and then gently let the breath out. Make sure she does not forcefully exhale because this will activate the superficial oblique and rectus abdomonis muscles. At the end of the expiration have the athlete cease breathing and then slowly and gently attempt to draw in the abdomen toward the spine. Once she has successfully accomplished the contraction, have her attempt to resume normal breathing. Often she will lose control of the contraction when she attempts to breathe normally.
Now, the idea is you do it that way and you will preferentially recruit the TVA and the MF. And there is some logic in that except of course it raises all sorts of other questions such as "normal breathing" for an athlete lying on the floor is not the same as normal breathing for an athlete in motion. And McGill would HAVE to have issue with that! He teaches us to develop an "athletic diaphragm" and you do NOT do that with your gut sucked in while relaxing on the floor.
Okay so there is still at least somethign to be said for that but the question is does all of that matter? CAN you isolate it really? I don't know and I DON'T care.
Getting into the MR and EC question and whether the back should be planted that is a sensitive issue and whats more important than the RA and all of that is whether you can do that without pain. They are assuming no active injury. If you do not functional range of motion in the pelvis that allows you to assume that position and do the exercise without pain then you should NOT be doing that.
Like I said before the idea of the dead bug is to train the TVA and all of that. But the reason and Joe brought it up and the reason that MR wrote about it is because it is really good for helping to correct the anterior pelvic tilt. If it were me I would not bothered too much with all the TVA this, RA that, and multifidinis whatever. You say that this week there will be another EMG study showing something and once again proving nothing. What matters to me is do the movements solve the problem. I dont' care if I'm contracting the damn RA or what. It's not like I'm going to be doing dead bugs for any other purpose but corrective..once the "correction" is made I'm not going to be thinking back and wondering about the individual muscles that were used. I'll leave that to guys doing EMG studies or hanging out in seminars debating it.
MR's method of using a flat back and an abdominal hollowing works very well as part of a stategy to correct APT. I think, if I recall the idea was the hollow for the TVA and MF and the flat back for the RA or something like that but I don't remember because I gloss over that stuff. Not out of disrespect for Mike but just because, in my experience anytime someone talks about individual muscles in things like this it leads me to ten million other questions that are really not all that important at the end of the day. DETAILS are the fuel of analysis paralysis.
But regardless tilting the pelvis posteriorly while in the hook lying position is not exactly the biggest feat in the world. But as you straighten the legs and you have tight hip flexors is becomes more and more difficult. The posterior pelvic tilt in a supine postion is both a way of grading the abdominals and a way of exercising them towards correcting anterior pelvic tilt. And "sucking in the gut" is a part of that correction. Remember it's not just the RA it's also obliques that are very important (btw what about tight hip flexors?).
The dead bug track, as it was conceived was just the abdominal hollowing, a neutral spine, and extremity movements. Combining that with posterior pelvic tilt makes for a very good way to correct APT assuming that the APT is part of a postural problem. However, I DON'T think it is necessary to have the back on the floor. Using a rolled up towel underneath the spine is fine if needed. It's the action of doing it that matters.
Are you confused by all of this? Because I've confused myself.
For example my APT is significant but my abs test well and the planks and strength and endurance tests.
I really think Joe is right on with his answer to that. To add to that it is part of the reason why McGill harps on breathing patterns, I think. You know many people can't properly engage their core while breathing heavy. When it comes to lifting (and McGill brings this up as well) it's totally different in terms of breathing. But as Joe said, getting down in a prone position and doing a nice leisurely plank is not really a good test for an actual dynamic athletic environment. It's much better for say, assessing whether you are good to go for deadlfits and things of that nature.
You are assuming also, with the abs, that anterior pelvic tilt is always accompanied by weak and elongated abdominals.
I don't think any of us here should really be trying to "diagnose" you though. All we can do is try to do the right thing and not make things worse. I am actually a little surprised by the idea of a physicaly therapists "diagnosing" a sports hernia because as we have discussed quite thouroughly there is no confidence in even a medical diagnosis of that involving imaging. I've heard lot's of coaches and what not throw around the term sports hernia whenever they hear groin pain and I don't think they have any business doing so.