by Dr M. C. Siff

Introductory Note

For newcomers, these P&Ps are Propositions, not facts or dogmatic proclamations. They are intended to stimulate interaction among users working in different fields, to re-examine traditional concepts, foster distance education, question our beliefs and suggest new lines of research or approaches to training. We look forward to responses from anyone who has views or relevant information on the topics.

Puzzle & Paradox 92

The debate about whether or not it is possible to separately exercise the upper and lower abdominal erector muscles may not have been definitively settled yet.

There is still considerable debate about whether or not it is possible to exercise separately the upper and lower portions of the recti abdominis muscles, especially since the recti constitute a single band of muscle between origin and insertion. Numerous books and fitness professionals refer to crunches and situps for the 'upper abs' (with the pivot being the distal rectus attachment on the pelvis), and pelvic curl or leg pushes into the air for the 'lower abs' (with the pivot being the proximal rectus attachment on the lowest ribs and spine).

EMG studies show that both the 'upper' and 'lower' abs show considerable electrical activity during both of these types of exercise, so that some authorities dismiss the idea of separate isolation exercise of the upper and lower abs.

Yet, a TV programme some years ago showed a belly dancer using her highly skilled abdominal musculature to roll a few quarters (US 25c pieces) up, down, diagonally and sideways across the belly. She concluded her unusual display by successfully folding a dollar bill placed on her belly. From this vaudeville display, it would certainly appear that it is possible to activate different parts of the abdominal musculature in skilled sequences. This might then suggest to the skeptic that it may be meaningful to talk about separate exercise of the upper and lower regions of the abs.

Of course, we must note that the effectiveness of most non-explosive exercises depends primarily on the amount of concentrated focus and voluntarily produced goal-directed muscle tension, so that one's visualization of the exercise would appear to have a profound effect on the pattern of activation of any muscle. This also depends on the patterns of breathing and breath-cessation used during the exercise.

Some authorities state that, since the different regions of the abdominals are separately innervated, one should certainly be able to activate upper and lower regions of the abs separately.

However, in saying that the lower abs are separately innervated we have to be cautious in misapplying this information. All of the rectus abdominis and the obliques are innervated by branches of the thoracic nerves T6 or T7 - T12, as is transversus (by the ventral rami and L1). This would tend to imply that the lower abs and lower obliques(?!) should be activated by stimulation of T6/7 - T8/9 and the upper abs and upper obliques (if these exist!) by the remaining thoracic nerves. In addition, an examination of their nervous innervation would also suggest that there should be separate activation of upper and lower transversus.

This clearly confounds the entire issue of trunk action and situps for the supposedly different parts of the trunk muscles. We can only resolve the issue if we stop talking about upper and lower abs etc and analyze in terms of a graduated activation of all of the trunk muscles progressing from the extreme top to the extreme bottom (as defined by the appropriate nerves) - much in the way that a caterpillar moves.

This would appear to offer a far more accurate and logical biomechanical approach, since the current view of upper vs lower abs would imply that there should be a somewhat jerky discontinuity somewhere during a full crunch. The entire action of trunk flexion is smooth, well-controlled and continuous, so this observation supports my view that there is a smooth continuum of activation of the entire abdominal (and erector spinae) group.

If one wishes to simplify, then it would be crudely accurate to talk of upper, mid and lower abs, but this still tends to mask the fact that there is really a continuum of muscle activation involving all of the trunk muscles, each exhibiting a different level of involvement, depending on the type and pattern of movement.

This means that it is highly unlikely that you will be able to totally isolate the 'lower abs', since there is always accompanying involvement of many other stabilizing and mobilizing muscles.

This, of course, has not answered the other issue which we raised earlier. If there is differential innervation of the obliques and transversus, must we then conclude that we should recognize upper and lower portions of these muscles, too? We have to bear in mind, even though essentially the same nerves are involved in activating the abdominal musculature, that different movement patterns have to be used to activate the different muscles.

Does this not imply then that one single exercise should be able to exercise all of the trunk muscles? Another point - if one sits up, then both the absand the obliques have to become involved in flexion, as a consequence of basic biomechanics - but what about transversus which is more strongly activated by coughing and forceful expulsion of air from the lungs (or by initiation of walking)?

Give your views on the concept of upper vs lower exercise of the abdominal musculature, including the obliques. Quote any relevant references or personal findings to corroborate your reply.

Dr Mel C Siff
School of Mechanical Engineering
University of the Witwatersrand
WITS 2050 South Africa
[email protected]

For more information email us at [email protected]