Latent myofascial trigger points: Their effects on muscle activation and movement efficiency

Kibler (Medicine and Science in Sports and Exercise 30 (1998) 79) suggests that when there is dysfunction in a proximal body segment, distal segments have to change workloads in order to preserve movement outcomes at the most distal body segment. One aspect of function is the timing of muscle activation. As the presence of pain could affect the muscle activation pattern (MAP), the effects of pain-free latent myofascial trigger points (LTrPs) in the scapular rotator muscle group were investigated. Surface electromyography was used to identify the MAP of the upper and lower trapezius, serratus anterior, infraspinatus and middle deltoid during scapular plane elevation. Repeated measures ANOVA was used to compare the control group (n=14) and the LTrP group (n=28). The LTrP group was then randomly assigned to either placebo intervention or true treatment to investigate the effect of removing the LTrPs. The data established that LTrPs in the scapular rotator muscles changes the MAP of this muscle group and of muscles further distal in the shoulder girdle kinetic chain. Treatment to remove LTrPs normalised the MAP.