Torque, Current, and Discomfort During 3 Types of Neuromuscular Electrical Stimulation of Tibialis Anterior

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Abstract
Background: The benefits of neuromuscular electrical stimulation (NMES) for rehabilitation depend on the capacity to generate functionally relevant torque with minimal fatigability and discomfort. Traditionally, NMES is delivered either over a muscle belly (mNMES) or nerve trunk (nNMES). Recently, we developed a technique that minimizes contraction fatigability by alternating pulses between the mNMES and nNMES sites, termed “interleaved” NMES (iNMES). However, discomfort and the ability to generate large torque during iNMES have not been explored adequately. Objectives: To compare discomfort and maximal torque between mNMES, nNMES and iNMES. Methods: Stimulation trains (12 pulses at 40 Hz) were delivered to produce dorsiflexion torque using mNMES, nNMES and iNMES. Discomfort was assessed using a visual analogue scale for contractions that generated 5–30% of a maximal voluntary isometric contraction (MVIC), and for the maximal tolerable torque. Results: Discomfort scores were not different between NMES types when torque was ≤20% MVIC. At 30% MVIC, mNMES produced more discomfort than nNMES and iNMES. nNMES produced the most torque (65% MVIC) followed by iNMES (49% MVIC) and mNMES (33% MVIC); in these trials, mNMES produced more discomfort than nNMES, but not iNMES. Limitations: The present results may be limited to individuals with no history of neuromusculoskeletal impairment. Conclusions: In terms of discomfort, there were no differences between mNMES, nNMES or iNMES for contractions between 5–20% MVIC. However, mNMES produced more discomfort than nNMES and iNMES for contractions of 30% MVIC, while for larger contractions, mNMES only produced more discomfort than nNMES. The advantages and disadvantages of each NMES type should be considered prior to implementation in rehabilitation programs.

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