Knee extensor force production and discomfort during neuromuscular electrical stimulation of quadriceps with and without gluteal muscle co-stimulation

Abstract

Purpose To investigate whether Neuromuscular Electrical Stimulation (NMES) simultaneously applied on the quadriceps (Q) and gluteal (G) muscles, as compared to single Q-stimulation alters the knee extensor force production and discomfort. Methods A total of 11 healthy participants (6 females), with normal weight and age between 19 and 54 years were included. The unilateral, isometric maximal voluntary contraction (MVC) was assessed for each participant in an isokinetic dynamometer (Biodex, system 3). NMES was, in a randomized order, applied only on the Q-muscle and on the Q- and G-muscles (QG) simultaneously. NMES-intensity was increased stepwise until the maximal tolerable level was reached regarding discomfort, graded according to the visual analogue scale (VAS). VAS and the % of MVC produced by NMES, were registered for each level, expressed as median (inter-quartile range). Results The maximum tolerated NMES-intensity applied on Q compared to QG resulted in equally high discomfort, 8.0 (6.0–9.0) vs 8.0 (6.3–9.0), and in equivalent knee extensor force production, 36.7 (29.9–47.5) and 36.2 (28.9–49.3), respectively, in % of MVC. At 20% of MVC, NMES applied on Q compared to QG resulted in equal acceptable discomfort, 3.0 (2.0–4.5) vs 3.0 (3–5.5), and comparable intensity levels, 41.5 (38.0–45.8) vs 43.5 (37.0–48.8), respectively. Conclusions Simultaneous QG-NMES, as compared to single Q-NMES, does not seem to affect the knee extensor force production or discomfort. Q-NMES, without voluntary muscle contraction, can with an acceptable level of discomfort result in at least 20% of MVC.

Global trends and hot topics in electrical stimulation of skeletal muscle research over the past decade: A bibliometric analysis

“…NMES is commonly used to artificially control voluntary contractions of skeletal muscle ( 71 , 72 ) and evaluate muscle performance or neuromuscular activation levels. The unique mechanism of NMES, but also a drawback, is the reversal of the regular voluntary recruitment pattern, which means the large and fatigable motor units are recruited earlier than smaller motor units ( 52 ).…”

Wide-pulse electrical stimulation of the quadriceps femoris allows greater maximal evocable torque than conventional stimulation

“…approximately 45% vs 40% MVC) could be translated into a potential benefit of 5% in terms of expected effectiveness. Several authors reported MET ranging from 25 to 90% MVC for the healthy quadriceps (8, 23), while the lower range of MET that is needed for strengthening effects has been suggested to be around 15-20% MVC (7, 16). Therapeutic window ranges of 25-50% and 15-25% MVC have also been advocated for healthy subjects/orthopaedic patients and cardiorespiratory patients, respectively (16).…”

“…The use of large electrodes (owing to reduced current density) (7), which has recently been recommended for an optimal application of NMES to the quadriceps femoris (16,19,22), could even lead to a greater proportion of subjects reaching MSO. In turn, this may lead to more subjects training at suboptimal workload (i.e.…”

“…Some subjects could approach or even reach the maximal stimulator output (MSO) of standard devices (∼100 mA), particularly following multiple NMES sessions, since tolerance to high-intensity NMES has been found to increase during a training program (8). The use of large electrodes (owing to reduced current density) (7), which has recently been recommended for an optimal application of NMES to the quadriceps femoris (16, 19, 22), could even lead to a greater proportion of subjects reaching MSO. In turn, this may lead to more subjects training at suboptimal workload (i.e.…”

The effect of neuromuscular electrical stimulation on the human skeletal muscle transcriptome

“…The NMES was delivered with a Chattanooga Physio (DJO Nordic, Malmoe, Sweden) with the same settings and intensity-increase as used in a previous study. 24 When the 20% of MVC was reached, the participants were asked to evaluate the general discomfort of the stimulation according to the Visual Analogue Scale (VAS) on a 100-step scale (0-10, with one decimal), with 0 indicating no discomfort or pain and 10 indicating the worst imaginable discomfort or pain. 34 All participants were informed that they could end the stimulation whenever they wanted but were encouraged to reach 20% of MVC.…”