The effect of an abdominal belt on trunk muscle activity and intra-abdominal pressure during squat lifts

Abstract

The purpose of this study was to determine whether abdominal belts such as those prescribed to industrial workers reduced trunk muscle activity and/or increased intra-abdominal pressure (IAP). In this study, six subjects lifted loads (72.7 to 90.9 kg) both with and without wearing a weightlifter belt. In addition, further trial conditions required that subjects lifted both with the breath held or continuously expiring on lifting effort. Dynamic hand loads were recorded together with intra-abdominal pressure (IAP) and abdominal, intercostal and low back EMG. Every subject demonstrated an increase in IAP when wearing the belt during both breathing conditions: 99 mmHg with no belt; 120 mmHg wearing belt (p less than 0.0001). However, it was also found that significant increases in IAP occurred (p less than 0.017) when the breath was held versus exhaling with or without the belt. One would expect that if the belt relieved either the direct compressive load on the spine or assisted IAP to produce an extensor moment then this would be reflected in diminished extensor muscle activity. Erector spinae activity tended to be lower with the breath held suggesting a reduced load on the lumbar spine although wearing a belt did not augment this reduction. In the case studies with subjects wearing an ergogenic corset designed for use by industrial manual materials handlers, perceptions of improved trunk stability were reported. However, the muscle activity and IAP results of this study during short duration lifting tasks make it difficult to justify the prescription of abdominal belts to workers.

Role of intra-abdominal pressure in the unloading and stabilization of the human spine during static lifting tasks

“…The magnitude of 9 kPa considered in this study for IAP in flexion tasks with load in hands is at the middle range of mean values reported in the literature (1-21 kPa) [2,31,36,44,52,53,55].…”

“…Experimental studies, however, have found that IAP increase is associated with a concurrent increase in the intradiscal pressure during Valsalva maneuvers [55] and no reduction in erector spinae activity in lifting [42,52]; thus raising questions on the unloading role of IAP. The co-contraction of abdominal muscles occurring along with an increase in IAP produces a flexor moment, large enough to offset or even exceed the IAP-generated extensor moment [11, 49,52].…”

“…The co-contraction of abdominal muscles occurring along with an increase in IAP produces a flexor moment, large enough to offset or even exceed the IAP-generated extensor moment [11, 49,52]. Large cross-sectional area of the diaphragm and the moment arm of the net IAP force considered in biomechanical model studies have been suggested to be the reason for overestimation of auxiliary extensor moment generated by IAP [49,51].…”

“…It has been reported to reach 50 kPa in power-competitive lifters wearing belt [52]. In neutral standing posture without carrying any load in hands, IAP has been measured as low as 0.2 kPa [2], 0.3 kPa [46], and 0.98 kPa [55].…”

“…The prevention, treatment, and rehabilitation programs would subsequently benefit from such improved knowledge. One parameter with the potential to influence spinal mechanics and stability is intra-abdominal pressure (IAP) that has been reported to increase during static and dynamics lifting tasks [1,5,24,27,34,45,46,52,54]. For years, it has been argued that an increase in IAP could unload the spine both directly by pressing upwards on the rib cage via diaphragm and indirectly by generating an extensor moment on the lumbar spine that decreases the back-muscle activities [5, 20-22, 31, 36-38, 41, 54].…”