THE EFFECT OF BACK BELTS ON LUMBAR MUSCLE FATIGUE

Study Design. An experiment was conducted to investigate the effect of wearing a weight lifting belt on the endurance and fatigue characteri stics of the extensor muscles of the spine. Objective. To evaluate the effectiveness of back belts in preserving the endurance characteristi cs of the spinal musculature. Summary of Background Data. Previous stu dies have investigated the use of back belts in increasing intra-abdom inal pressure and thus increasing the stabilization of the spine. Othe r studies have looked at the association of low back disability and we aring beck belts. No study has examined the relationship between weari ng back belts and measures of spinal muscle fatigue and endurance. Met hods. Thirteen male industrial workers performed a lifting and lowerin g task from the floor to a 76.2 cm height at 4.3 min(-1) 2 days a week for 4 weeks. The load was psychophysically determined and averaged 28 .1 kg for a total of 28.9 metric tons moved in 4 hours. Subjects lifte d for 1, 2, 3, and 4 hours, respectively, for the first 4 days of the experiment. These were considered training days. During the last 4 day s, subjects lifted for 4 hours per day; 2 days with a back belt, and 2 days without a back belt. Maximum isokinetic endurance of the extenso rs was measured for 50 repetitions (5 sets of 10 repetitions) at the e nd of 4 hours of lifting. Median frequencies of the electromyographic signal from six locations over the back extensors were measured for 30 seconds at 80% of maximum isometric voluntary contraction after 4 hou rs of lifting. Results. There were no significant differences in maxim um isokinetic endurance, or in the slope of median frequency, between lifting with a back belt and lifting without a back belt. Similarly, a modified Borg scale and a postexperiment survey question were unable to distinguish between wearing a back belt and not wearing a back belt . Conclusion. There were no significant differences in maximum isokine tic endurance and electromyographic spectral parameters of the back ex tensor muscles as a result of wearing a back belt during heavy lifting and lowering tasks.