Muscle pain induces task-dependent changes in cervical agonist/antagonist activity

Area of Science:

• Neuromuscular Physiology
• Pain Research
• Biomechanics

Background:

• Neck muscle pain is common and can affect motor control.
• Understanding the EMG-force relationship is crucial for assessing muscle function.

Purpose of the Study:

• To investigate how experimental neck muscle pain influences the electromyography (EMG)-force relationship in cervical agonist and antagonist muscles.
• To determine if pain affects muscle activation patterns and muscle fiber conduction velocity.

Main Methods:

• Surface EMG and muscle fiber conduction velocity (CV) were measured in 14 healthy subjects during controlled cervical contractions.
• Neck muscles (sternomastoid, splenius capitis, upper trapezius) were subjected to pain induction via hypertonic saline injection.
• EMG average rectified value (ARV) and CV were analyzed across varying force outputs (0-60% MVC) before and after pain induction.

Main Results:

• Induced sternomastoid pain during flexion reduced sternomastoid ARV on the painful side and decreased bilateral splenius capitis and upper trapezius ARV.
• Induced splenius capitis pain during extension lowered splenius capitis ARV on the painful side and increased bilateral upper trapezius ARV.
• No significant changes in sternomastoid ARV or muscle fiber CV were observed in response to pain during extension or flexion.

Conclusions:

• Experimental neck muscle pain induces task-dependent alterations in cervical muscle activation patterns.
• Pain affects the coordinated activity of agonist and antagonist muscles during specific neck movements.
• Muscle fiber conduction velocity remains unaffected by experimentally induced neck muscle pain in this context.