Electrical Currents for Muscle Contraction Flashcards
The use of electrical currents to produce muscle contractions in innervated muscles is called what?
neuromuscular electrical stimulation (NMES)
What 5 things can NMES be used for?
- Stroke
- SCI
- Sports-related injury
- Postoperative conditions
- Healthy athletes
What are the 5 things NMES-stimulated contractions can do?
- Strengthen muscle
- Improve cardiovascular health
- Retard or prevent muscle atrophy
- Reduce spasticity
- Restore function
What is the difference between muscle contractions produced by electrically stimulated action potentials (APs) and those produced by physiologically initiated APs?
- With PI contractions, the smaller nerve fibers (and thus the smaller, slow-twitch type I muscle fibers) are activated first
- With ES muscle contractions, the largest-diameter nerve fibers (and thus the larger, fast-twitch type II muscle fibers) are activated first
The large, fast-twitch type II muscle fibers stimulated via electrical stimulation produce what type of contraction? What are 2 other characteristics of them?
They produce the strongest and quickest contractions. However, they fatigue rapidly and atrophy rapidly with disuse.
The smaller, slow-twitch type I muscle fibers physiological initiated produce what type of contraction? What are 2 other characteristics of them?
They produce lower-force contractions that do not fatigue as easily and do not atrophy as easily
When is electrical stimulation useful?
When you want to specifically strengthen muscle fibers weakened by disuse
What should the patient do to optimize the functional integration of strength gains produced by NMES?
They should perform BOTH ES and PI contractions
Should rest times be long or short for NMES? Explain why…
Long rest times should be utilized due to the muscle fatigue
In regards to onset of contraction how do ES and PI contractions differ?
- PI contractions gradually increase in force in a smooth graded manner
- ES contractions tend to have a rapid, jerky onset
Why is ES onset rapid and jerky?
because all motor units of a given size fire simultaneously when the stimulus reaches motor threshold
ES strengthens muscle via what 2 principles?
- Overload
- Specificity
What does the overload principle state?
The greater the load placed on a muscle and the higher force contraction it produces, the more strength that muscle will gain
What type of contractions can the overload principle be applied to?
Both ES and PI
How can the load be increased with PI contractions?
by increasing resistance
How can the load be increased with ES contractions?
- Increasing the amount of current
- Adjusting pulse duration and amplitude
- Adjusting electrode size
- Increasing externally applied resistance
What does the specificity principle state?
Muscle contractions specifically strengthen the muscle fibers that contract
Because ES has more of an effect on larger, fast-twitch type II muscle fibers, what type of patient is it optimal in and why?
ES can be used post-surgically, post-immobilization to amplify and accelerate strength gains
What are 3 possible reasons why ES may amplify and accelerate strength gains in post-surgical patients?
- May enhance the quality of motor recruitment
- May carry over to improved performance of functional activities
- May initially have a force of as little as 10% of MVIC
To increase _____, higher-force contractions should be used
strength
To increase ______, prolonged stimulation with more lower-force contractions should be used
endurance
NMES plus voluntary exercise can increase strength in what muscle following TKA?
quadriceps
What 3 non-surgical orthopedic conditions can benefit from NMES? Describe how each can benefit…
- Osteoarthritis: decreases pain and increases strength
- Rheumatoid Arthritis: reverses muscle weakness and atrophy
- Patellofemoral Syndrome: increases VMO strength
E-stim can be used to increase strength and improve motor control in patients with CNS damage under what conditions?
as long as the peripheral motor nerves are intact
What 5 neurological disorders can benefit from NMES?
- Spinal Cord Injury
- Stroke
- Traumatic Brain Injury
- Multiple Sclerosis
- Cerebral Palsy
Gains can be made in neurological disorders through the use of NMES in what 3 ways?
- Muscle strengthening
- Increased general excitability of the motor neuron pool
- Sensory input cueing