A comparison of torque generating capabilities of three different electrical stimulating currents

Area of Science:

• Biomechanics
• Rehabilitation Engineering
• Exercise Physiology

Background:

• Neuromuscular electrical stimulation (NMES) is widely used in rehabilitation.
• Different NMES devices possess varying current characteristics that may influence torque production.
• Understanding these differences is crucial for optimizing therapeutic outcomes.

Purpose of the Study:

• To compare the torque-generating capabilities of three commercial NMES devices.
• To assess the efficacy of different NMES units in eliciting muscle contractions.
• To determine if NMES devices can provide sufficient overload for strength progression.

Main Methods:

• Twenty healthy adults participated in the study.
• Maximal voluntary isometric knee extension torque was measured using an isokinetic dynamometer.
• Two 10-second, maximally tolerated contractions were elicited with each of the three NMES devices.
• Elicited torque was expressed as a percentage of maximal voluntary isometric torque (%MVIT).

Main Results:

• A significant difference in %MVIT was observed among the NMES devices.
• NMES 2 (Nemectrodyn 7) produced significantly lower %MVIT compared to NMES 1 (Electrostim 180-2) and NMES 3 (Chattanooga VMS).
• NMES 2 reached its maximal current output in most participants, indicating a limitation in its capacity.

Conclusions:

• While all tested NMES devices can produce torque sufficient for strengthening, NMES 2 demonstrated lower torque output.
• NMES 2 may not be suitable for implementing the principle of "overload" necessary for progressive strength gains.
• Device-specific current characteristics significantly impact NMES efficacy in eliciting torque.