Electromyographic fatigue analysis of back muscles during remote muscle contraction.

Objectives: To compare back muscle endurance during the trunk holding test with and without remote muscle contraction using electromyographic (EMG) power spectral analyses. Methods: Eleven healthy male subjects were studied during the unsupported trunk holding test without grip power and with 20% and 50% grip power. Surface electrodes were placed over each erector spinae muscle at L1 level. Median frequency (MF) and mean power frequency (MPF) were evaluated by the ME3000P Fast Fourier Transform spectral analysis program. The rate of change was determined for each parameter during the test, and significance was examined by the Wilcoxon matched-pair signed-rank test. Results: Both MF and MPF decreases with 20% grip power were significantly faster than without grip power (p=0.003 and 0.012). Both indices decreases with 50% grip power were significantly slower than with 20% grip power (MF: p=0.004, MPF: p=0.041). Conclusion: Changes in back muscle endurance by remote muscle contraction were confirmed using EMG power spectral analysis. We found that back muscle endurance with 20% grip power was lower than without remote muscle contraction, and the endurance with 50% grip power increased than with 20% grip power. [ABSTRACT FROM AUTHOR]