Differential activation of scapular muscles, during arm elevation, with and without trigger points

Area of Science:

• Biomechanics
• Neuromuscular control
• Sports medicine

Background:

• Latent Myofascial Trigger Points (LMTrPs) are pain-free hyperirritable spots in muscle taut bands.
• LMTrPs can alter muscle activation patterns during movement, impacting functional mechanics.
• This study focuses on upper trapezius LMTrPs and their effect on scapular rotator activation.

Purpose of the Study:

• To investigate the onset of upward scapular rotator muscle activations during rapid arm elevation.
• To compare muscle activation patterns in patients with upper trapezius LMTrPs versus healthy controls.
• To analyze muscle activation across three distinct planes of arm movement.

Main Methods:

• Evaluated muscle onset timing for Upper Trapezius (UT) and Serratus Anterior (SA) during arm elevation in three planes.
• Used Deltoid (DEL) muscle activation as the reference point for timing.
• Compared muscle activation latencies between LMTrP patients and a healthy control group.

Main Results:

• Significant differences in relative muscle latencies were observed between groups.
• Individuals with LMTrPs demonstrated delayed and inconsistent UT activation in all movement planes (p < 0.05).
• Delayed SA activation was noted during flexion in the LMTrP group (p < 0.05).

Conclusions:

• Both primary and synergistic muscles show delayed activation and altered recruitment patterns during rapid arm elevation in LMTrP patients.
• These motor control alterations may represent adaptive strategies in response to upper trapezius LMTrPs.
• Findings highlight the neuromuscular impact of LMTrPs on shoulder complex function.