Electromechanical delay during functional electrical stimulation induced cycling is a function of lower limb position

Area of Science:

• Biomedical Engineering
• Rehabilitation Science
• Neuroscience

Background:

• Functional electrical stimulation (FES) cycling aids rehabilitation for movement disorders.
• FES introduces an electromechanical delay (EMD) between stimulation and muscle force onset.
• Optimizing FES requires understanding factors influencing EMD.

Purpose of the Study:

• To investigate the effect of cycle crank angle on EMD during FES cycling.
• To determine if limb position influences the delay between FES and muscle torque production.

Main Methods:

• Experiments involved 10 participants (5 healthy, 5 with neurological conditions).
• FES was applied to quadriceps and gluteal muscles at various crank angles (10° increments).
• Electromechanical delay was assessed via contraction delay (CD) and residual delay (RD) using two measurement techniques and regression analysis.

Main Results:

• The cycle crank angle was found to be a statistically significant factor for both contraction delay (CD) and residual delay (RD).
• This indicates that limb position directly influences the timing of muscle force generation in response to FES.

Conclusions:

• The crank angle significantly affects the electromechanical delay (EMD) in FES cycling.
• Future FES models and control systems should incorporate crank angle for improved accuracy and rehabilitative outcomes.
• This research informs the development of closed-loop FES cycling systems for enhanced rehabilitation.