An electromyographic study of elbow motion during postexercise muscle soreness

Area of Science:

• Exercise Physiology
• Muscle Biology
• Biomechanics

Background:

• Postexercise muscle soreness, often experienced after eccentric contractions, is a common phenomenon.
• The underlying mechanisms causing the associated reduction in range of motion and muscle swelling remain incompletely understood.
• Previous hypotheses have implicated neuromuscular factors in the restricted movement.

Purpose of the Study:

• To investigate the cause of restricted motion associated with postexercise muscle soreness.
• To differentiate between neuromuscular and connective tissue contributions to reduced elbow flexion and extension.
• To examine the role of electromyographic activity during passive muscle stretching in sore muscles.

Main Methods:

• Inducing delayed-onset muscle soreness (DOMS) in human elbow flexors via eccentric contractions.
• Measuring range of elbow motion and arm diameter before and 48 hours post-exercise.
• Conducting electromyographic (EMG) assessments, including resting levels and activity during isometric and passive movements.

Main Results:

• Eccentric exercise induced muscle soreness, characterized by reduced elbow range of motion and increased arm diameter (swelling).
• Electromyographic (EMG) activity did not increase during passive stretching of the sore elbow flexors.
• The observed resistance to passive extension was not linked to stretch reflex activation.

Conclusions:

• Neuromuscular activity does not explain the restricted motion observed in postexercise muscle soreness.
• Edematous changes (swelling) within the perimuscular connective tissue are the likely cause of altered muscle elasticity and restricted motion.
• These findings highlight the role of connective tissue alterations in the pathophysiology of DOMS.