Comparison of maximum voluntary isometric contraction to normalize superficial neck muscle EMG

The aim of this study was to evaluate the effectiveness of different strategies to obtain the highest value during a maximum voluntary isometric contraction (MVIC) of the sternocleidomastoid and anterior scalene muscles. Fourteen healthy subjects without neck disability were evaluated with surface EMG on the sternocleidomastoid and anterior scalene muscle with the BTS FreeEMG 1000. Three MVIC techniques were performed, one was the Conventional MVIC with neck flexion, a Rotated MVIC with neck lateral flexion with a rotated neck, and also the Lateral Flexion MVIC in a side position performing a neck lateral flexion. All MVIC's were randomly performed three times with the head and trunk resisted by an adjustable band. A 0.5s RMS moving window was used to smooth the signal and the peak value was acquired. Non-parametric Friedman Test was used to compare MVIC and also a Wilcoxon test for two-by-two MVIC comparisons with a Bonferroni correction. Statistically, the highest EMG activation was reached in the Rotated MVIC for the sternocleidomastoid and in the Conventional MVIC for the Anterior Scalene. Therefore, it is suggested to perform these two types of MVIC in order to normalize both sternocleidomastoid and anterior scalene muscles.