Lumbar spine stability can be augmented with an abdominal belt and/or increased intra-abdominal pressure

The increased intra-abdominal pressure (LAP) commonly observed when the spi ne is loaded during physical activities is hypothesized to increase lumbar spine stability. The mechanical stability of the lumbar spine is an importa nt consideration in low back injury prevention and rehabilitation strategie s. This study examined the effects of raised IAP and an abdominal belt on l umbar spine stability. Two hypotheses were tested: (1) An increase in IAP l eads to increased lumbar spine stability, (2) Wearing an abdominal belt inc reases spine stability. Ten volunteers were placed in a semi-seated positio n in a jig that restricted hip motion leaving the upper torso free to move in any direction. The determination of lumbar spine stability was accomplis hed by measuring the instantaneous trunk stiffness in response to a sudden load release. The quick release method was applied in isometric trunk flexi on, extension, and lateral bending. Activity of 12 major trunk muscles was monitored with electromyography and the IAP was measured with an intra-gast ric pressure transducer. A two-factor repeated measures design was used (P < 0.05), in which the spine stability was evaluated under combinations of t he following two factors: belt or no belt and three levels of LAP (0, 40, a nd 80% of maximum). The belt and raised IAP increased trunk stiffness in al l directions, but the results in extension lacked statistical significance. In flexion, trunk stiffness increased by 21% and 42% due to 40% and 80% IA P levels respectively; in lateral bending, trunk stiffness increased by 16% and 30%. The belt added between 9% and 57% to the trunk stiffness dependin g on the TAP 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 effect on the activity of any of the muscles with the exception of the thoracic erector spinae in extension and the lum bar erector spinae in flexion, whose activities decreased. The results indi cate that both wearing an abdominal belt and raised IAP can each independen tly, or in combination, increase lumbar spine stability. However, the benef its of the belt must be interpreted with caution in the context of the decr eased activation of a few trunk extensor muscles.