Comparison of healthy and LBP Median Frequency slopes. (A) Erector Spinae, (B) Gluteus Maximus, and (C) Biceps Femoris. In all graphs, time to exhaustion was normalized to 100% for direct comparison between subjects and groups. Error bars indicate one standard deviation of the mean. Using a one-way ANOVA, significant differences in MF were found in the erector spinae muscle at 90–100% of the performance time while no significant differences were found in either the gluteus maximus or biceps femoris muscles.