Determining the optimal maximal and submaximal voluntary contraction tests for normalizing the erector spinae muscles

Abstract

Background. This study aimed to identify which maximum voluntary isometriccontraction (MVIC) and sub-MVIC tests produce the highest activation of the erectorspinae muscles and the greatest reduction in inter-individual variability, to put themforward as reference normalization maneuvers for future studies.Methods. Erector spinae EMG activity was recorded in 38 healthy women during fivesubmaximal and three maximal exercises.Results. None of the three MVIC tests generated the maximal activation level in allthe participants. The maximal activation level was achieved in 68.4% of cases with thetest performed on the roman chair in the horizontal position (96.3±7.3;p<0.01).Of the five submaximal maneuvers, the one in the horizontal position on the romanchair produced the highest percentage of activation (61.1±16.7;p<0.01), and oneof the lowest inter-individual variability values in the normalized signal of a trunkflexion-extension task.Conclusions. A modified Sorensen MVIC test in a horizontal position on a romanchair and against resistance produced the highest erector spinae activation, but not in100% of participants, so the execution of several normalization maneuvers with thetrunk at different inclinations should be considered to normalize the erector spinaeEMG signal. A modified Sorensen test in a horizontal position without resistance isthe submaximal maneuver that produces the highest muscle activation and the greatestreduction in inter-individual variability, and could be considered a good reference testfor normalization.