Functional Electric Stimulation: Technical Parameters & the Myocycle

Last year ReWalk Robotics began a distribution partnership with MYOLYN for their user friendly FES bike, the Myocycle. During that time we had to as a team dig into the PT school vault for those fond memories of modalities class to refresh which each FES parameter represents and how it affects treatment decisions. Hear from our west coast Business Development Manager Matt Fuller, PT, DPT as he reviews these important concepts and how the Myocycle uniquely helps clinicians make the most of FES interventions.

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4 FES parameters that are most widely utilized and discussed:

1. Pulse Width (or duration): length of time that a single pulse is applied to the muscle group.
2. Frequency: number of pulses delivered each second, measured by Hz. Importance of stimulation frequency is related to torque or muscle power output and muscle fatigue. These effects are positively correlated; Increased frequency = greater power & increased (Faster) muscle fatigue. 
3. Amplitude: Amplitude is related to size of muscle or deeper stimulations. Current is controlled to have greater control of flow of the electrons in the tissue.
4. Waveforms: Waveforms are a visual description of the stimulation pulse. Different waveforms can stimulate different muscles groups, sizes, and depth. Waveforms effect torque, comfort, and skin irritation.

The Myocycle provides 2 adjustable stimulation variables: 

1. Pulse Width:
   • Range = 0, 20-500 microseconds
   • Identified on main screen by levels 0-20. Arrows are used to adjust the pulse width up or down. 
   • Controlled bilaterally; equal pulse width between left and right leg
2. Amplitude:
   • 3 levels = 50 mA, 90 mA, 120 mA
   • Identified on main screen by Low, Med, High when selecting muscle group highlighted white icons (Quads, Hams, Glutes) on either lower extremity.
   • Allows for increased amplitude on individual muscle groups on either leg, giving the Myocycle increased control and personalization of stimulation.

The other 2 stimulation variables are pre-set for optimal efficiency, effectiveness, and ease-of-use.

1. Frequency:
   • Set to 60 Hz; based on research of FES frequency, 60 Hz is most efficient. Balanced between strength of contraction and onset of muscle fatigue.
2. Waveform:

• The Myocycle uses a Biphasic, rectangular, and symmetrical pulse. Good for stimulating large muscle groups, while producing greater torque and increased patient comfort.

To learn more about FES, read this blog from MYOLYN here

To see the Myocycle in action, click below: