Evaluating the Relationship Between Muscle Activation and Spine Kinematics Through Wavelet Coherence

Area of Science:

• Biomechanics
• Neuroscience
• Physiology

Background:

• Understanding the relationship between muscle activation and joint motion is crucial for analyzing dynamic tasks.
• Time-frequency analysis offers advanced methods to explore complex muscle-movement interactions.
• Electromyography (EMG) measures muscle activation, while kinematics describes motion.

Purpose of the Study:

• To investigate the relationship between lumbar spine kinematics and trunk muscle activation using wavelet coherence.
• To compare the coherence and phase relationships between lumbar erector spinae, internal oblique, and spine motion.
• To explore how differing muscle functions might explain observed activation-motion patterns.

Main Methods:

• Utilized wavelet coherence analysis to compare surface EMG linear envelope of trunk muscles with lumbar spine flexion-extension kinematics.
• Focused on a fundamental cyclical movement to analyze muscle activation and motion synchronization.
• Examined coherence at specific frequencies (0.25, 0.5, and 1.0 Hz) and analyzed coherence phase plots.

Main Results:

• Both lumbar erector spinae and internal oblique muscles demonstrated coherence with spine kinematics at the main cyclic frequency.
• Lumbar erector spinae exhibited significantly higher coherence with spine kinematics compared to the internal oblique at 0.25, 0.5, and 1.0 Hz.
• Phase plots revealed that lumbar erector spinae precedes trunk extension at 0.25 Hz, while internal oblique is in phase with spine kinematics.

Conclusions:

• The distinct coherence and phase characteristics of lumbar erector spinae and internal oblique suggest functional differences in spine movement control.
• Lumbar erector spinae's role as a primary mover may explain its stronger coherence and leading phase, while internal oblique's stabilizing role aligns with its in-phase relationship.
• Wavelet coherence is a valuable tool for assessing how factors like pain, pathology, or fatigue impact the muscle activation-motion relationship.