Accelerated Muscle Fatigability of Latent Myofascial Trigger Points in Humans

Authors

  • Hong-You Ge MD, PhD,

    Corresponding author
    1. Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark
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  • Lars Arendt-Nielsen Dr. Med. Sci., PhD,

    1. Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark
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  • Pascal Madeleine Dr. Med. Sci., PhD

    1. Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark
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  • Conflict of interest/disclosure: The Danish Working Environment Authority (“Undersøgelse af manifestationer, årsagsmekanismer samt progression af smerter hos computerbrugere” project) is acknowledged for their support. The authors have no conflicts of interest to report.

Hong-You Ge, MD, PhD, Center for Sensory-Motor Interaction, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark. Tel: +45-99-40-87-99; Fax: +45-98-15-40-08; E-mail: ghy@hst.aau.dk.

Abstract

Objective.  Muscle fatigue is prevalent in acute and chronic musculoskeletal pain conditions in which myofascial trigger points (MTPs) are involved. The aim of this study was to investigate the association of latent MTPs with muscle fatigue.

Design.  Intramuscular electromyographic (EMG) recordings were obtained from latent MTPs and non-MTPs together with surface EMG recordings from the upper trapezius muscles during sustained isometric muscle contractions in 12 healthy subjects.

Outcome Measures.  Normalized root mean square (RMS) EMG amplitude and mean power frequency (MNF) were analyzed. The rate of perceived exertion and pain intensity from MTP side and non-MTP side were recorded.

Results.  Pain intensity on the MTP side was significantly higher than the non-MTP side (P < 0.05). Intramuscular EMG from latent MTPs showed an early onset of decrease in MNF and a significant decrease at the end of fatiguing contraction as compared with non-MTPs (P < 0.05). Surface EMG from muscle fibers close to latent MTPs presented with an early onset of the increase in RMS amplitude and the increase was significantly higher than that from non-MTPs at the end of sustained isometric contraction (P < 0.05).

Conclusions.  A latent MTP is associated with an accelerated development of muscle fatigue and simultaneously overloading active motor units close to an MTP. Elimination of latent MTPs and inactivation of active MTPs may effectively reduce accelerated muscle fatigue and prevent overload spreading within a muscle.

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