Current Events
On most clinical electrical stimulation units, this parameter is essentially your “intensity” dial.
A. Frequency
B. Pulse duration
C. Current/amplitude
D. Ramp time
What is... C. Current/amplitude.
BONUS: What unit measures amplitude?
What are two major factors influencing muscle force production discussed in the lecture?
Electrodes should ideally encompass the ________ of the targeted muscle.
Motor point.
BONUS: What is motor mapping and how do you do this?
A reasonable example starting point for motor stimulation is:
A. 150 Hz, 50 μsec
B. 20 Hz, 200 μsec
C. 2 Hz, 50 μsec
D. 100 Hz, 1 ms
B. 20 Hz, 200 μsec
BONUS: Explain why you chose this.
You turn on stimulation and your patient immediately says it feels uncomfortable.
What's the wrong response?
A. Reconsider electrode size/placement
B. Examine pulse duration
C. Examine intensity
D. Say, “The machine knows best.”
😂 D. “You are smarter than the machine!”
Your patient has very dry skin and significant adipose tissue over the target muscle. What electrical concept should immediately come to mind?
Increased impedance/resistance. Dry skin, callus, lotions/oils, and adipose tissue can increase impedance.
BONUS: What would you change to address this?
Roughly what frequency range is associated with unfused tetany in the lecture?
A. 1 to 2 pps
B. 3 to 20 pps
C. 50 to 100 pps
D. 100 to 150 pps
B. 3 to 20 pps
Which electrode is generally more comfortable?
A. Smaller
B. Larger
B. Larger, because the stimulation is distributed across a greater surface area.
Your contraction is jerky and you haven't achieved tetany yet. Which parameter would you try increasing first?
Frequency. Increasing frequency can improve the quality of tetany until a smooth fused contraction is achieved
Before choosing parameters, what comes first?
A. Pick the frequency
B. Select your favorite stim unit
C. Identify the patient's goals
D. Turn amplitude up until something happens
C. Identify the patient's goals.
According to Ohm’s Law, resistance increases but you want to maintain the same current. What needs to happen?
A. Voltage decreases
B. Voltage increases
C. Frequency increases
D. Pulse duration decreases
B. Voltage increases. The lecture describes the relationship as I=V/RI=V/RI=V/R, so greater resistance requires greater voltage to maintain a constant current.
You increase frequency. What happens to muscle force and fatigue?
Force generally increases, but fatigue also increases. The clinical goal is therefore often to find the lowest frequency capable of producing the desired tetanic contraction
Why might you intentionally choose a smaller electrode?
To improve selectivity and minimize unwanted electrical bleed into neighboring muscles, provided it can still recruit the desired muscle.
The stimulation is “bleeding” excessively into neighboring muscles. What's a good first parameter adjustment?
Decrease pulse width/pulse duration. Decreasing intensity may also help, and a smaller electrode may improve targeting.
A patient has a pacemaker. Does that automatically mean “absolutely no stimulation anywhere”?
Implanted electrical devices are treated as a precaution requiring individualized medical/team consideration.
Talk to your physician, obtain cardiology clearance, and avoiding electrode placement over implanted devices.
*Electrical stimulation should not be used with on-demand pacemakers.
Which usually has the higher current density, a small electrode or a large electrode?
Small electrode. Current density has an inverse relationship with electrode size.
Which one is characterized by synchronous recruitment?
A. Volitional contraction
B. Electrically stimulated contraction
B. Electrically stimulated contraction. Stimulated contractions recruit motor units in a much more synchronous pattern, which contributes to greater fatigue.
For shoulder subluxation, what two muscles are given as a typical starting electrode placement?
Posterior deltoid and supraspinatus. Other placement options may be appropriate based on the direction of the subluxation and unwanted muscle recruitment.
A patient is fatiguing rapidly during prolonged FES.
What parameter should you consider decreasing first?
Frequency. The lecture specifically identifies reducing frequency as the first adjustment when attempting to minimize fatigue.
A patient has significant long-term atrophy. The muscle responds sluggishly to stimulation.
According to the lecture, what parameter modification may help?
Increase pulse width/pulse duration, along with considering a longer overall treatment time.
BONUS: Which device would you use for this?
Neuroplasticity Jackpot
Why is it preferable, when possible, to pair FES with the patient's own effort and an actual functional task?
Coupling electrical stimulation with effort is important for muscle recruitment and cortical representation. The stimulation should support meaningful activity rather than simply creating an isolated contraction whenever possible.
Why does an electrically stimulated contraction tend to fatigue more rapidly than a voluntary contraction?
Electrical stimulation produces synchronous recruitment, so the motor units under the electrode are activated together rather than rotating activity asynchronously as occurs with voluntary recruitment.
You stimulate the supraspinatus for shoulder subluxation but keep recruiting too much upper trapezius.
What's an alternative muscle placement?
Infraspinatus
Same Charge Challenge
You increase pulse duration but want approximately the same total charge under the curve.
What should happen to amplitude?
Decrease amplitude. Longer pulse duration can be paired with lower amplitude to obtain an equivalent charge under the curve.
🏆 Therapist's Choice
Before applying e-stim, name four questions the therapist should be asking.