Dr. Michael Hartle
Medical Committee Chair
Trunk Stabilization Concepts and Exercises
by Michael A. Hartle, D.C., D.A.C.B.N., C.C.N., C.C.S.P., C.S.C.S., E.M.T.
Part Three of Six
Wohlfahrt D, Jull G, Richardson C. The relationship between dynamic and static function
of abdominal muscles. Aust Physiother 1993; 39(1): 9-13.
This study looked at 38 subjects and divided them into 2 groups, those who were
able to perform more than 51 abdominal crunch exercises and those who can perform
fewer than 51. The subjects were soldiers for whom crunches were a part of their
regular training regimen. They also analyzed the speed at which the subjects performed
the exercises. The soldiers had been trained to perform crunches at a 1 repetition
per 3 seconds cadence, and the researchers noticed that some would perform them
slowly, each rep lasting the full three seconds, while others performed them quickly,
the rep lasting only one second with 2 seconds rest in between. They measured spinal
stabilization ability with a 4-cell pressure sensor that was placed under the lumbar
spine of the study subjects to measure sagittal plane and rotational movements and
with progressive exercises involving movements of the lower extremities while attempting
to maintain stability of the lumbar spine.
The results showed that the greater number of reps the subjects were able to perform
in the crunch test, the greater their spinal stabilization capacity. But the stability
capacity was even more dependent on the speed at which the crunches were performed
in training, i.e., those who performed their crunches faster exhibited poorer stabilization
capacity and those who performed their crunches more slowly exhibited greater stabilization
capacity. This finding is consistent with other studies by this and other groups
that have shown that fast movements improve power at the expense of stability. When
performing crunches quickly, the rectus abdominis dominates the movement. When they
are performed slowly, the abdominal obliques and transverse (and, probably the multifidus)
are utilized. This demonstrates that for stabilization training, it is important
for movements to be performed slowly so that the appropriate muscles can be recruited
in the pattern that maximizes the efficiency of the stabilizing system of the spine.
Hodges PW, Richardson CA. Contraction of the abdominal muscles associated with movement
of the lower limb. Phys Ther 1997; 77:132-144.
In the first study the authors used fine wire and needle EMG to record the activity
in the transverse abdominis, internal oblique, external oblique, multifidus, rectus
abdominis, gluteus medius, tensor fascia lata (TFL), rectus femoris and gluteus
maximus to assess the relative contraction latencies between the trunk stabilizers
and the prime movers of the hip. They had 15 healthy subjects move their right hip
into flexion, abduction and extension and recorded the activity.
With hip flexion, all the trunk muscles except the external oblique contracted to
stabilize before the rectus femoris contracted to move the thigh. The transverse
abdominis was the first muscle to contract in all subjects. With abduction, only
the transverse abdominis and internal oblique contracted to stabilize before the
TFL. With extension, the transverse abdominis, rectus abdominis and internal oblique
contracted before the gluteus maximus. So the transverse abdominis was the only
muscle that contracted proactively to act as a stabilizer of the trunk with all
hip movements. The multifidus contracted proactively to stabilize with all movements
except hip extension. (Murphy)
Hides JA, Richardson CA, Jull GA. Multifidis muscle recovery is not automatic after
resolution of acute, first-episode low back pain. Spine 1996; 21(23):2763-2769.
Study number three looked at chronic low back pain patients and healthy controls
and measured EMG activity in the erector spinae and multifidis when a 2 kg weight
attached to a shoulder harness was dropped from 45 cm to create a sudden, unexpected
They found that the EMG activity of the multifidis that was seen as a response to
a sudden, unexpected load was found to be delayed and smaller in magnitude in the
chronic low back pain patients as compared to healthy controls. This suggests that
these patients do not have good reaction time or recruitment in the multifidis and
so they have to try to compensate for it with the muscles of the lower extremities.
These last two studies demonstrate that the transverse abdominis and multifidis
are important in contracting to stabilize the spine prior to extremity movements.
To be able to do this, they must be able to react very quickly. When sudden forces
are acted upon the body, there is a very small time period in which these muscles
must contract strongly to protect the area where they are located from injury.
The mutlifidus responds to injury by becoming inhibited and wasted. Once the injury
resolves and the pain is gone, the multifidus wasting does not automatically resolve.
This inhibition is demonstrated by the inability to react and contract quickly when
a force or load is acted upon the body. Acute low back pain is usually perceived
to be "self-limiting", however, the rate of recurrence in the first year is up to
80%. The multifidus, with the wasting and inhibition that can occur during acute
injury, may be one of the major factors responsible for the high rate of recurrence.
Ng J, Richardson C. Reliability of electromyographic power spectral analysis of back
muscle endurance in healthy subjects. Arch Phys Med Rehabil 1996;77:259-264.
Biering-Sorensen F. Physical measurements as risk indicators for low-back trouble
over a one-year period. Spine 1984;9: 106-119.
Luoto S, Heliovaara M, Hurri H, Alaranta H. Static back endurance and the risk of
low-back pain. Clin Biomech 10:6;323-324, 1995.
The above three studies reference an important muscle that one must not overlook
in regards to the proper health and function of the spine: multifidus. This muscle,
in some places the size of your pinky finger, contracts and helps stabilize the
spine in concert with the contraction of the transverse abdominis (pulling your
abdominals in). The multifidus is a primary intersegmental stabilizer of the spine.
It has a short reaction time due to its location near the center of rotation of
the vertebrae. It is the primary muscle active during static back extensor endurance
testing (i.e., Sorensen's test), where poor endurance has been found to be able
to predict first time onset of lower back pain (LBP) in healthy individuals and
recurrence rates in those recovering from LBP.
Liebenson C (ed) Spinal Rehabilitation: A Manual of Active Care Procedures. Williams
and Wilkins, Baltimore 1996.
Liebenson discusses what happens to the multifidus with low back pain (LBP). Type
2 fiber atrophy has been found in chronic LBP and disc patients. Moth eaten changes
have been confirmed in type 1 fibers. Muscular atrophy has been found in acute LBP
patients and was greatly improved with stabilization training. Again, confirming
the above studies regarding the wasting of the mutlifidus and its role in LBP.
Next Issue... To Belt or Not to Belt! That is the Question...
Michael A. Hartle,
USA Powerlifting Executive Committee Board Member
Chairman, USA Powerlifting Sports Medicine Committee
Chairman, USA Powerlifting Drug Testing Committee
USAPL Suspension List
For the latest USAPL Suspension List,