Comparison of peak torque, intensity and discomfort generated by neuromuscular electrical stimulation of low and medium frequency

Abstract

BACKGROUND AND PURPOSE: Neuromuscular electrical stimulation (NMES) is an important tool in clinical practice to improve the recruitment of motor units. Optimal forms of NMES, as well as the optimal frequency to achieve the highest torque with the least possible discomfort are not well established. This study was designed to compare maximum electrically-induced torque (MEIT) in the quadriceps, the maximum intensity tolerated by the subject, and the level of discomfort generated by three types of stimulation. METHODS: Thirty subjects (mean age of 25.0 ± 3.0 years) participated in the study. Each subject was submitted to three currents: medium frequency (2500 Hz) modulated in low frequency (Russian Current), and two currents of low frequency (50 Hz), i.e. without an intrapulse interval (FES), and another with an intrapulse interval of 100 µs (VMS). The maximum voluntary isometric torque (MVIT) of the quadriceps was measured. The MEIT, the level of discomfort, and the maximum intensity reached were also measured while applying the three types of NMES. The order of the tests was randomized and the torque was normalized in relation to MVIT. RESULTS:The results showed no significant difference between the three types of NMES in relation to the generated torque. However, the subjects were able to tolerate a significantly higher intensity with the medium frequency current, and suffered less discomfort when compared to subjects exposed to low frequency currents. CONCLUSION: Russian Current, FES, and VMS can be used clinically in order to increase the torque of the quadriceps muscle. However, we suggest using the Russian Current in the early stages of a rehabilitation protocol because it showed better tolerance by the participants with less discomfort.

Effects of combined application of progressive resistance training and Russian electrical stimulation on quadriceps femoris muscle strength in elderly women with knee osteoarthritis

“…The ES used in this study was Russian current: pulse frequency of 50 Hz, burst duration of 10 ms, symmetric pulses of sinusoidal form, with a duty cycle of 25% (5 seconds/20 seconds) and a pulse duration of 400 μs. The anterior area of the thigh of the affected limb was cleaned with alcohol, and four self-adhesive electrodes were placed on the limb: one electrode on the rectus femoris, two electrodes on the proximal and distal area of the vastus lateralis, and one electrode on the vastus medialis 7 ) . After placing the electrodes on the subject’s thigh, the subject was instructed to inform the maximum level of tolerance and contract the QFM while the PRT was performed.…”

Comparison of the effects of kilohertz- and low-frequency electric stimulations: A systematic review with meta-analysis

“…Table 1 shows the characteristics of the included studies that compared the effects of PC and KFAC. All included studies had a within-subject repeated design[ 9 , 13 , 14 , 34 – 44 ]. A total of 271 subjects (mean age: 26.4 years) were included from 14 studies.…”

“…[ 11 ] It is also important to emphasize that the effects estimate comparing KFAC and PC treatments in the previous meta-analysis had wide 95% confidence intervals (CIs),[ 8 ] which could change the clinical decision if the true effects estimates are in the upper or lower boundary. [ 12 ] Recently, additional relevant articles were reported [ 13 , 14 ]; therefore, precision of effects estimate would be increased by synthesizing all these articles. These updated information would be helpful for clinicians and physical therapists in making and improving evidence-based treatment regimen using NMES for muscle strength.…”

Use of Russian and Aussie Current in Isometric Tetanization of the Quadriceps Femoris

“…It is also required to identify a current that promotes the ideal stimulus to generate strength with the least clinically possible muscle discomfort. 10 In-depth studies of the physical properties of the Aussie and Russian currents and their interaction with the biological system are required to elucidate the mechanisms that make these currents act differently in individuals, providing a basis for explaining the results.…”

“…At the kilohertz level (2000 to 4000Hz), impedance is very low, dissipating less electrical energy in the epidermis and a greater proportion of electrical energy is available to stimulate the underlying tissue, allowing the stimulation of motor nerves. 9,10 The higher the frequency of the carrier wave, the more efficient and less uncomfortable will be the stimulation of the deeper motor nerves. [11][12][13] However, the motor nerves do not respond to frequencies in the kilohertz range, requiring their modulation in low-frequency ranges.…”