Myogram: Understanding Muscle Tension & Contraction Recording

A myogram is a graphical recording of muscle tension or contraction dynamics over time. It captures the mechanical and/or electrical events of muscle activation.

Two Primary Modalities

1. Electromyography (EMG)

• Records electrical activity (action potentials) from muscle fibers.
• Surface EMG: Non-invasive; global muscle activity.
• Needle EMG: Invasive; single motor unit analysis.
• Key metrics: MUAP (amplitude, duration, phases), CMAP (amplitude, latency), recruitment pattern, interference pattern.
• Uses: Neuromuscular diagnosis (neuropathy, myopathy, NMJ disorders), rehab biofeedback, kinesiology research.

2. Mechanomyography (MMG)

• Records mechanical oscillations (lateral displacement, pressure, acceleration) during contraction.
• Sensors: Accelerometers, piezoelectric, laser distance, microphones.
• Metrics: Amplitude (force proxy), frequency (fiber type/fatigue), onset/offset timing.
• Advantages: Non-invasive, no electrical crosstalk, reflects contractile mechanics directly.
• Uses: Fatigue monitoring, spasticity assessment, prosthetic control, sports science.

Clinical & Research Applications

• Diagnose denervation vs. myopathy.
• Quantify spasticity (MAS correlation).
• Optimize FES parameters.
• Evaluate rehab interventions.
• Study motor control strategies.

Interpretation Requires Expertise

Artifacts (movement, ECG, noise), electrode placement, temperature, muscle length, and subject cooperation all affect signals. Normative databases are modality- and muscle-specific.

Myograms translate muscle physiology into actionable data.