The influence of contraction duration in muscle energy technique applied to the atlanto-axial joint

Abstract

Abstract Muscle Energy Technique (MET) has been advocated for the treatment of restricted range of motion in the upper neck. There is little evidence, however, to support the effectiveness of MET to increase motion in the cervical spine, or determine the optimal duration of isometric contraction during the technique. The aim of this study was to investigate the effect of various durations of MET isometric contractions on active atlanto-axial rotation range of motion. 52 asymptomatic subjects (age range 18–43) who displayed a unilateral active atlantoaxial rotation asymmetry of 4° or more were randomly allocated to either a 5 (n=17) or 20-second (n=18) isometric contraction MET group, or a sham (n=17) treatment control group. Active atlanto-axial end-range measurements were recorded pre and post-intervention, and the examiner was blinded to group allocation. Analysis with a one-way ANOVA revealed significant differences (P=0.04) in the mean change between the 5-second MET group and the control, but not between the 20-second MET group and control. MET using 5-second contractions produced the largest mean increase in rotation, both to the restricted (+6.65°) and non-restricted sides (+0.71°). The 5-second MET produced a large pre-post effect size (d=1.01), whereas the 20-second MET (d=0.68) and control (d=0.33) produced moderate and small effect sizes, respectively. This study failed to demonstrate a significant benefit in the use of a longer (20-second) isometric contraction when treating the upper cervical spine with MET. The use of a 5-second isometric contraction appeared to be more effective than longer contraction durations for increasing cervical range with MET, but further investigation is recommended.