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The effect of back belts on lumbar muscle fatigue
1Liberty Mutual Research Center for Safety and Health, Hopkinton, Massachusetts, USA.
Study Design:
An experiment was conducted to investigate the effect of wearing a weight lifting belt on the endurance and fatigue characteristics of the extensor muscles of the spine.
Objective:
To evaluate the effectiveness of back belts in preserving the endurance characteristics of the spinal musculature.
Summary Of Background Data:
Previous studies have investigated the use of back belts in increasing intra-abdominal pressure and thus increasing the stabilization of the spine. Other studies have looked at the association of low back disability and wearing back belts. No study has examined the relationship between wearing back belts and measures of spinal muscle fatigue and endurance.
Methods:
Thirteen male industrial workers performed a lifting and lowering 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 lifted 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 days, 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 extensors was measured for 50 repetitions (5 sets of 10 repetitions) at the end 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 hours of lifting.
Results:
There were no significant differences in maximum 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 isokinetic endurance and electromyographic spectral parameters of the back extensor muscles as a result of wearing a back belt during heavy lifting and lowering tasks.