Electrically Elicited Muscle Torque: Comparison Between 2500-Hz Burst-Modulated Alternating Current and Monophasic...

Area of Science:

• Biomedical Engineering
• Rehabilitation Science
• Neuromuscular Physiology

Background:

• Neuromuscular electrical stimulation (NMES) is crucial for quadriceps strengthening post-knee surgery.
• Muscle torque production, key for strength gains, is often limited by patient discomfort during NMES.
• Burst-modulated alternating current (BMAC) is a common NMES waveform, while monophasic pulsed current (MPC) has shown effectiveness for high torque output.

Purpose of the Study:

• To compare knee extensor muscle torque production between BMAC and MPC at maximum tolerated intensity.
• To evaluate the efficacy of different NMES waveforms in eliciting muscle torque.

Main Methods:

• A single-blind, block-randomization crossover design was employed with 20 healthy adults.
• Participants received NMES via MPC and BMAC to their dominant or nondominant lower extremity.
• Stimulation intensity was increased to maximum tolerance, with torque measured as a percentage of maximum volitional isometric contraction.

Main Results:

• Monophasic pulsed current (MPC) elicited significantly higher torque (49.5% ± 19.6% of MVC) compared to burst-modulated alternating current (BMAC) (29.8% ± 12.4% of MVC).
• The difference in torque production between MPC and BMAC was statistically significant (P = .002).
• Treatment order and limb tested did not influence torque production.

Conclusions:

• Neuromuscular stimulation with MPC is potentially more effective than BMAC for generating high torque output.
• MPC may be a superior waveform for enhancing quadriceps strength in individuals experiencing weakness.