Physical Agents: EMG biofeedback

What is biofeedback?

Technique which enables the individual to readily determine the activity levels of a particular physiological process, and with appropriate training, learn to manipulate the same process by an internalized mechanism

Why is biofeedback used?

Usually implemented to facilitates the users ability to self-regulate a targeted biological process to enhance performance or as part of a comprehensive treatment plan for a specific medical condition

How does EMG biofeedback differ from other modalities?

Biofeedback requires the user to learn how to control the targeted process using attentional strategies to create therapeutic or performance effect

What are the two types of biofeedback?

direct and transformed

Describe direct biofeedback

Produces accurate external representation of the internal biological process

What are the examples of direct biofeedback

heart rate monitor

Describe transformed biofeedback

Provides externally processed information representative of the internal biological process

What are examples of transformed biofeedback

EMG and EEG

What types of extrinsic signals can be created?

Auditory, visual, or haptic (tactile)

What do the EMG electrodes represent and what do they not represent

represent electrical changes in the activity of the muscle, but are not a DIRECT representation of the ability to generate muscle tension/contraction or muscle strength

What do narrow electrodes target?

superficial msucles

What do wider electrodes target?

Deeper tissue with less specificity

How does gel affect the electrodes?

It will increase the conductance and decrease the noise from the environment

when would you use higher of lower gain?

i. Higher gains are used when user only have trace muscle contractions
ii. Lower gains are used when you want the user to have to contract with greater effort

what is "shaping"?

adjusting the gain to control the target process (increasing will make it harder for the patient // decreasing with make it easier for the patient to hit the target)

What is contraction latency?

The time between a command to contract a muscle and the point at which peak amplitude is achieved; usually about 5 seconds

What is return latency?

The time it takes for the electrical activity in muscle to return to resting levels following a command to relax; about 1 second

What is hold capacity?

The ability of the muscle to maintain a contraction over time as determined by the stability of measured EMG activity, reflection of the endurance of a muscle

When is above threshold used?

A threshold that requires the patient to increase the level of myoelectric activity to produce an EMG signal

When is below threshold used?

A threshold that requires the patient to decrease the level of myoelectric activity to produce and EMG signal

What are the three main physiologic effects of EMG biofeedback?

Neuromuscular facilitation, inhibition, and coordination

What are the characteristics of facilitation?

a. Reduces the AMI effect which increased the muscles ability to reach maximal force (MVIC)
b. increases motor unit recruitment
c. Decreases latency
d. Increased neural excitation

What are the characteristics of inhibition?

a. Used to inhibit myoelectric activity of muscle
b. Decreases tone
c. User attempts to decrease the signal or intensity

What are the characteristics of coordination?

User works with the feedback to try and increase timing and intensity of muscle recruitment for specific task

What is Arthrogenic Muscle Inhibition?

a. When there is injury/surgery that leads to pain and swelling it will inhibit the normal muscle function
b. This is a protective mechanism
c. It will lead to atrophy, weakness, long term disability

What are the clinical indications for EMG?

a. Hemiplegia
b. Quad strengthening
c. Headache
d. Pelvic floor disorders
e. Chronic pain conditions
f. TMJ disorders

What are the contraindications for EMG biofeedback?

a. Acute inflammatory conditions (where activities might aggravate or disrupt healing process)
b. Pregnancy
c. Bladder or vaginal infection
d. Allergy to electrode or contact material
e. Do not place over the eyes or sensitive tissue

What are the precautions for EMG biofeedback?

a. Diminished skin sensation
b. Patients with epilepsy may experience adverse effects

What are possible adverse effects of EMG biofeedback?

a. Dyspnea, fatigue, angina, or other cardiac related symptoms
b. DOMS
c. Skin irritation from electrodes
d. Increased pain if used inappropriately

What outcomes might be assessed as part of an EMG biofeedback intervention

a. Pain
b. ROM
c. Palpation
d. Strength