Evaluation of human dynamic contraction by phonomyography.

Area of Science:

• Biomechanics
• Muscle Physiology
• Biomedical Engineering

Background:

• The phonomyogram (PMG), or acoustic myogram, is known to increase with force during isometric muscle contractions.
• Its utility in dynamic contractions, particularly concerning varying inertias, requires further investigation.

Purpose of the Study:

• To investigate the relationship between PMG and muscle force during dynamic elbow flexion contractions against different inertias.
• To compare PMG with surface electromyogram (EMG) and mechanical acceleration during these dynamic contractions.

Main Methods:

• Simultaneously recorded PMG, surface EMG from biceps and brachioradialis, and angular acceleration during self-initiated elbow flexions.
• Movements were performed against two different inertias over a 30-degree range.
• Integrated PMG (iPMG) and integrated EMG (iEMG) were calculated from signal onset to the end of the acceleration phase. Phono- and electromechanical delays were also measured.

Main Results:

• A linear relationship was observed between iPMG and force, with the slope independent of inertia.
• Both iPMG and iEMG showed a linear relationship with angular acceleration, with slopes dependent on inertia.
• Phonomechanical delay followed EMG onset but preceded acceleration onset, suggesting PMG reflects muscle contractile element tension.

Conclusions:

• The phonomyogram (PMG) provides a convenient method for evaluating muscle tension during dynamic human contractions.
• The linear relationship between iPMG and force, independent of inertia, highlights its potential as a simple force transducer.
• PMG's ability to reflect muscle contractile element activity makes it a valuable tool in biomechanical assessments.