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Shoulder kinematic and muscle recruitment pattern changes in upper trapezius myofascial trigger points: a controlled
Maliheh Rahmati1, Farid Bahrpeyma2, Mohammed N Ashtiani3
1Department of Physiotherapy, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box 14115-111, Tehran, Iran.
BMC Musculoskeletal Disorders
|December 26, 2025
Summary
Myofascial trigger points in the upper trapezius alter shoulder coordination, leading to increased scapulohumeral rhythm and prolonged muscle activation rise time during abduction. These findings highlight subtle neuromuscular changes associated with trigger points.
Area of Science:
- Biomechanics
- Neuromuscular Physiology
- Sports Medicine
Background:
- Myofascial trigger points (MTrPs) in the upper trapezius are common in shoulder pain patients.
- MTrPs can disrupt neuromuscular control and shoulder movement kinematics.
Purpose of the Study:
- To compare shoulder muscle activation and kinematics, specifically scapulohumeral rhythm (SHR), between individuals with and without upper trapezius MTrPs during shoulder abduction.
Main Methods:
- Observational study comparing a trigger point group (n=15) and a healthy group (n=13).
- Surface electromyography (EMG) measured activation of eight shoulder muscles.
- Kinematic analysis assessed SHR, scapular, and glenohumeral motion.
Main Results:
- No significant differences in peak EMG amplitudes or timing were found between groups.
- The trigger point group showed a significantly prolonged muscle activation rise time (p<0.001).
- The trigger point group exhibited an increased SHR (p=0.026), indicating altered glenohumeral-scapular coordination.
Conclusions:
- Upper trapezius MTrPs are linked to altered shoulder coordination, evidenced by increased SHR and prolonged muscle activation rise time.
- Advanced EMG timing analysis combined with kinematic assessments may offer sensitive markers for MTrP-related neuromuscular changes.
