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From: [log in to unmask] <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 20 April 2000 12:55
Subject: BELTS & LIFTING


>Here are a few interesting articles on belt use and stabilisation of the
>spine.  Note that none of these studies involved any specific focus on the
>possible role played by TA (transversus Abdominis) in trunk stabilisation,
>but showed that increased Intra-abdominal Pressure (IAP) and activation of
>the back muscles suffices to achieve stabilisation under conditions of
loaded
>lifting.
>
>Note that one of the articles shows that belt wearing does not decrease
>activity of the trunk muscles while lifting, as is often claimed by those
who
>oppose belt wearing.  Instead, the EMG activity of all 12 trunk muscles
>increases significantly in all three directions due to the increased IAP.
>
>Another article showed that the activity of the oblique abdominal muscles
>when lifting decreased after isometric abdominal training, thereby
suggesting
>that the typical type of slow abdominal exercise like "crunches" may have
>
>Another noteworthy observation is that maximum activity of the abdominal
>muscles appears long before the peak of the IAP, and that this lag between
>the two peaks may compromise lifting safety. On the other hand, if the IAP
>were to peak before the abdominal muscles, an inadequate "pressure wall"
>might exist to contain the increased pressure.  This finding might lend
>further weight to the recommendation that one should not exceed about 70%
of
>one's maximum breath holding capability during heavy lifting (Vorobyev A
>"Textbook on Weightlifting"  1978).
>
>------------------------
>
>Miyamoto K et al   Effects of abdominal belts on intra-abdominal pressure,
>intra-muscular pressure  in the erector spinae muscles and myoelectrical
>activities of trunk muscles.   Clin Biomech (Bristol, Avon) 1999 Feb;
>14(2):79-87
>
>Intra-muscular pressure of the erector spinae muscles increases
significantly
>by wearing an abdominal belt during Valsalva maneuvers and during maximum
>isometric  lifting exertions, while maximum isometric lifting capacity and
>peak intra-abdominal pressure are not affected. Electrical activity of
rectus
>abdominis increases significantly by wearing an abdominal belt during
>Valsalva maneouvres (after full inspiration) and during isometric leg
>lifting.
>
>It is concluded that wearing abdominal belts raises intra-muscular pressure
>of the erector spinae muscles and appears to stiffen the trunk. Assuming
that
>increased intra-muscular pressure of the erector spinae muscles stabilizes
>the lumbar  spine, wearing abdominal belts may contribute to the
>stabilization during lifting exertions.
>-------------------------------
>
>Cholewicki J et al    Lumbar spine stability can be augmented with an
>abdominal belt and/or  increased intra-abdominal pressure.   Eur Spine J
>1999;8(5):388-95
>
>The belt and raised IAP (Intra-abdominal pressure) increased trunk
stiffness
>in all directions, but the results in extension lacked statistical
>significance. In flexion, trunk stiffness increased by 21% and 42% due to
40%
>and 80% IAP levels respectively; in lateral bending, trunk stiffness
>increased by 16% and 30%. The belt added between 9% and 57% to the trunk
stiff
>ness depending on the IAP level and the direction of exertion. In all three
>directions, the EMG activity of all 12 trunk muscles increased
significantly
>due to the elevated IAP.
>
>The belt had no positive or negative effect on the activity of any of the
>muscles, with the exception of the thoracic erector spinae in extension and
>the lumbar erector spinae in flexion, whose activities decreased. The
results
>indicate that both wearing an abdominal belt and raised IAP can each
>independently, or in combination, increase lumbar spine stability. However,
>the benefits of the belt must be interpreted with caution in the context of
>the decreased activation of a few trunk extensor muscles.
>----------------------------------------------
>
>Cresswell A, Blake P & Thorstensson A   The effect of an abdominal muscle
>training program on intra-abdominal pressure. Scand J Rehabil Med 1994 Jun;
>26(2):79-86
>
>The effect of 10 weeks' specific abdominal strength training (resisted
trunk
>rotations) on intra-abdominal pressure was investigated in 10 healthy
males.
>Isometric rotational force, trunk flexor and extensor torque and
>intra-abdominal pressure were measured as well as intra-abdominal pressure
>responses to Valsalva manoeuvres, maximal pulsed pressures, drop jumps and
>trunk perturbations.
>
>Rotational strength increased 29.7% after training without significant
change
>in intra-abdominal pressure. The isometric flexor strength did not change,
>while the extensor strength increased 11.0%. Valsalva and pulsed pressures
>increased 11.6 and 9.2%, respectively. The rate of intra-abdominal pressure
>development during pulsed pressures, drop jumps and trunk perturbations
>increased after training. The level of intra-abdominal pressure during the
>latter two tasks remained unchanged.
>
>It is  concluded that an increase in strength of the trunk rotators with
>training improves the ability to generate  higher levels of voluntarily
>induced intra-abdominal pressure and increases the rate of intra-abdominal
>pressure development during functional situations.
>
>-------------------------------------
>
>Hemborg B et al     Intraabdominal pressure and trunk muscle activity
during
>lifting--effect of abdominal muscle training in healthy subjects.  Scand J
>Rehabil Med 1983;15(4):183-96
>
>Twenty healthy young men went through intense isometric training of the
>abdominal muscles for five weeks. Before and after training the subjects
were
>put through a standardized test programme, measuring the strength of
>abdominal and back muscles, and a series of lifts, 10, 25, and 40 kg, leg
>lifts and back lifts. The intraabdominal pressure (IAP), and the EMG
activity
>of the oblique abdominal muscles, and of the erector spinae muscle were
>recorded.
>
>It was found  that:
>
>1.  The strength of the trunk flexors increased markedly after abdominal
>training. The activity of the oblique abdominal muscles when lifting
>decreased after abdominal training, i.e. motor unit recruitment was not
>improved.
>
>2.  The IAP at lifting was not affected by abdominal training.
>
>3.  The activity of the oblique abdominal muscles was of no decisive
>importance to the IAP.
>
>4.  The strength of the back muscles increased, but the activity of the
back
>muscles at lifts was not affected by abdominal training. In back lifts
there
>was no detectable activity of the back muscles during the beginning of the
>lifting and during a great part of the lowering.
>
>5.  In back lifts the maximum activity of the abdominal muscles appeared
long
>before the peak of the IAP, which may be of  importance with regard to the
>development of inguinal hernia.
>-------------------------------------------
>
>Cholewicki J, Juluru K & McGill S   Intra-abdominal pressure mechanism for
>stabilizing the lumbar spine.
>J Biomech 1999 Jan;32(1):13-7
>
>Two distinct mechanisms for stabilising the spine were simulated separately
>and in combination. One was antagonistic flexor-extensor muscle
coactivation
>and the second was abdominal muscle activation along with generation of
IAP.
>
>Both mechanisms were effective in stabilizing the model of a lumbar spine.
>Both  mechanisms were also effective in providing mechanical stability to
the
>spine model when activated simultaneously. The breath-holding IAP mechanism
>for stabilizing the lumbar spine appears preferable in tasks that demand
>trunk extensor moment such as lifting or jumping. This mechanism can
increase
>spine stability without the additional coactivation of the erector spinae
>muscles of the back.
>-----------------------------------------
>
>Dr Mel C Siff
>Denver, USA
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