Do This For A Stronger Core
Done correctly, the crunch is an effective exercise for those wanting
to work their abs with minimum stress to the lower back.
Research shows that the crunch — also called the curl-up,
the abdominal curl, or the trunk curl — has a high "challenge-to-compression"
ratio [1].
In other words, it challenges your abs while imposing minimal compressive
load to the spine.
The usual advice is to "pull your belly button in toward your
spine" or "pull your abs in" during the crunch. But
there's a far better way to make the exercise more effective.
In fact, researchers from Omaha's University of Nebraska Medical
Center have found that "pulling the abs in" actually reduces
rectus abdominis activity [2]. Learn
more about the abdominal muscles (pop-up window).
A group of 25 subjects performed the crunch in accordance with
different sets of instructions.
The first set of instructions was intended to emphasize rectus
abdominis activity. The second set of instructions was intended
to emphasize the obliques.
Electromyographic activity was recorded from the upper and lower
rectus and the internal and external oblique abdominis muscles.
A physical target was used to make sure that the trunk was raised
to the same height for all conditions.
The crunch worked rectus abdominis harder when subjects were told
to tighten their stomach muscles, rather than pull them in. Here
are the instructions they were given:
"Push your belly button out by tightening your stomach muscles.
Try to shorten the distance between the bottom of the ribs and
the groin area when you curl up. Focus on drawing your ribcage
down and in while you curl up."
But the same exercise worked the external and internal obliques
more than rectus addominis when these instructions were given:
"Try to suck in your stomach to move your belly button toward
the floor. Keeping your stomach tight, try to flatten your back
against the floor. Focus on keeping your ribcage flared out as
you curl up."
Professor Stuart McGill, an expert in spine function and injury
prevention at the University of Waterloo in Canada, offers the following
tips for those wanting an advanced version of the crunch with minimal
stress to the spine:
• One leg is bent with the knee flexed to 90° while
the other leg remains relaxed on the floor.
• No cervical (upper spine) motion should occur, either
chin poking or chin tucking.
• For anyone experiencing neck discomfort, place the tongue
on the roof of the mouth behind the front teeth, which helps to
promote stabilizing neck muscle patterns.
• Brace the abdominals. This involves tightening the abdominal
muscles as if you're about to take a punch in the gut. When the
brace is performed correctly, the abdominal wall is neither hollowed
in nor pushed out.
• Curl up against the brace, and then breathe deeply in
the "up" curl-up position while maintaining the brace.
Remain in the up position long enough to take a few deep breaths.
This technique will challenge rectus abdominis while minimizing
compressive load to the lumbar spine. Try it the next time you train
your abs. You'll be surprised at how such a simple exercise can
easily be made more challenging and effective.
About The Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
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References
1. Axler, C.T., & McGill, S.M. (1997). Low back loads over
a variety of abdominal exercises: searching for the safest abdominal
challenge. Medicine
and Science in Sports and Exercise, 29, 804-811
2. Karst, G.M., & Willett, G.M. (2004). Effects of specific
exercise instructions on abdominal muscle activity during trunk
curl exercises. Journal
of Orthopaedic and Sports Physical Therapy, 34, 4-12
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