UNIT 3 DP 3

What Is EMG Biofeedback?

EMG (Electromyographic) Biofeedback measures and records electrical activity produced by muscles, giving real-time information (feedback) to patients and clinicians.

Key Points:

The device does not deliver current (unlike NMES or FES).

It detects the voltage changes caused by active muscle fibers.

Information is displayed visually and/or auditorily to guide the patient’s response.

Commonly used to increase or decrease muscle activation depending on the goal.

Example:

Electrodes placed over the vastus medialis record quadriceps activity during knee extension after ACL reconstruction. The patient matches their contraction intensity to visual feedback on a screen.

🎯 Purposes and Indications

Facilitatory Biofeedback Inhibitory Biofeedback

Used when muscle activation is weak or inhibited Used when muscles are overactive or spastic

Promotes strengthening and recruitment Promotes relaxation and tone reduction

Common in orthopedic cases (e.g., ACL repair, post-surgery weakness) Common in neurological cases (e.g., stroke spasticity, chronic pain spasms)

⚡ Electrode Setup and Placement

Electrodes:

Use disposable adhesive electrodes, similar to those used in electrical stimulation.

The muscle fibers closest to the electrodes are detected.

Placement Rules:

Wide placement: Detects a larger muscle volume; used for facilitatory training.

Narrow placement: Detects a smaller, localized signal; used for inhibitory training.

The muscle should be partially innervated for signal detection.

No contraindications—since no current is delivered.

📈 Sensitivity and Gain Settings

Sensitivity = ability to detect electrical activity of a muscle.

Gain = level of amplification applied to that signal.

They are inversely related:

Setting Sensitivity Description

Low gain (1 µV) High sensitivity Detects tiny muscle activity; ideal for weak muscles early post-op

High gain (1000 µV) Low sensitivity Detects only strong signals; used once the muscle has improved strength

💪 Clinical Example: ACL Reconstruction

Early Stage (Facilitatory):

Quadriceps weak and unable to contract voluntarily.

Set high sensitivity (low gain, 1 µV) → detects minimal activity.

Encourages early contraction awareness.

Later Stage (Progression):

Patient achieves 60% of strength in the affected limb.

Set low sensitivity (high gain, 500 µV) → requires stronger contractions for feedback.

Promotes greater muscle recruitment and endurance.

🧩 Clinical Decision-Making with Biofeedback

Ask yourself the following when planning biofeedback treatment:

Is the patient appropriate?

Good for patients unable to tolerate electrical stimulation but capable of voluntary effort.

Which muscle to monitor?

Select based on functional limitation (e.g., quadriceps post-ACL, wrist extensors post-stroke).

What is the goal?

Facilitation (strengthen/recruit) or inhibition (relax/decrease spasticity)?

What sensitivity is needed?

High sensitivity early (weak activity)

Low sensitivity later (stronger activity)

What electrode placement?

Close together: Inhibitory (focused relaxation)

Wide apart: Facilitatory (broad activation)

How will parameters progress?

As strength improves → reduce sensitivity (increase gain) and integrate functional tasks.

🩺 Example Applications by Diagnosis

Diagnosis Goal Biofeedback Use

Post-ACL Reconstruction Facilitation Increase quadriceps activation using high sensitivity early, progressing to lower sensitivity as strength improves

Stroke (CVA) Inhibition Reduce flexor tone in arm/forearm muscles using narrow electrode placement

Chronic Low Back Pain Inhibition Teach relaxation and control of paraspinals

Shoulder Impingement Facilitation Strengthen scapular stabilizers for improved motor control

🧠 Practical Setup Steps

Explain purpose, device, and feedback method to the patient.

Prepare skin (clean and dry).

Place electrodes on target muscle (wide or narrow depending on goal).

Set device sensitivity:

High for weak muscles (facilitation).

Low for strong muscles (progression).

Provide feedback cues:

Visual (screen bars, graphs) or auditory (tones).

Encourage repetition and consistency.

Monitor progress—adjust sensitivity as muscle activation improves.