Latent Myofascial Trigger Points are Associated With an Increased Antagonistic Muscle Activity During Agonist Muscle Contraction

José Miota Ibarra, Hong-You Ge, Chao Wang, Vicente Martínez Vizcaíno, Thomas Graven-Nielsen, Lars Arendt-Nielsen - The Journal of Pain, Volume 12, Issue 12, December 2011, Pages 1282–1288

Summary and Review by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

Reasons Why the Study Was Performed:

The aim of the study was to investigate the effect of latent (non-symptomatic) motor trigger points on muscle activity in an antagonist muscles (opposing muscle) during agonist muscle contraction (isometric).  In this case latent trigger points were evaluated in the posterior deltoid during isometric shoulder flexion at 25% of maximal voluntary contraction.  This study demonstrated the occurrence of “altered reciprocal inhibition” due to the presence of motor trigger point involvement.

This study may also serve as a model for future researchers -  the use intramuscular electromyography is paramount when studying this relationship; surface electromyography was insufficient in detecting increased motor unit (motor trigger point) activity.

The methodology that was employed:

This study included 14 health subjects.  The level of activity within the muscles tested (the posterior deltoid) was measured using intramuscular electromyography (EMG).  A needle was inserted into a latent motor trigger point (MTP) or a non-MTP at rest and during isometric shoulder flexion performed at 25% of maximum voluntary contraction.  Surface EMG was also recorded on the anterior and