Literature ReviewEffects of Kilohertz Frequency, Burst Duty Cycle, and Burst Duration on Evoked Torque, Perceived Discomfort and Muscle Fatigue A Systematic ReviewModesto, Karenina Arrais Guida MSc; Bastos, Júlia Aguillar Ivo MSc; Vaz, Marco Aurélio PhD; Durigan, João Luiz Quagliotti PhD Author Information From the Department of Physical Education, University of Brasilia, Brasilia, Brazil (KAGM); Rehabilitation Sciences Program, University of Brasilia, Brasilia, Brazil (JAIB, JLQD); and Human Movement Sciences Graduate Program (PPGCMH), School of Physical Education, Physiotherapy and Dance (ESEFID), Federal University of Rio Grande do Sul (UFRGS), RS, Brazil (MAV). All correspondence should be addressed to: Karenina Arrais Guida Modesto, MSc, Department of Physical Education, Darcy Ribeiro University Campus, Brasília-DF | CEP 70910-900 - Brazil. This article was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES Finance Code 001), the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq process number: 404746/2018-7; 312136/2018-8), the Fundação de Amparo à Pesquisa do Distrito Federal (FAPDF process number 00193.0000168/2019-87), Decanato de Pesquisa e Inovação (DPI process number: 02/2021; DPG process number: 02/2021), and the Graduation Program of Physical Education (PPGEF process number: 09/2021). Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.ajpmr.com). American Journal of Physical Medicine & Rehabilitation 102(2):p 175-183, February 2023. | DOI: 10.1097/PHM.0000000000001982 Buy SDC Metrics Abstract Kilohertz-frequency alternating current is used to minimize muscle atrophy and muscle weakness and improve muscle performance. However, no systematic reviews have evaluated the best Kilohertz-frequency alternating current parameters for this purpose. We investigated the effects of the carrier frequency, burst duty cycles, and burst durations on evoked torque, perceived discomfort, and muscle fatigue. A search of eight data sources by two independent reviewers resulted in 13 peer-reviewed studies being selected, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and rated using the PEDro scale to evaluate the methodological quality of the studies. Most studies showed that carrier frequencies up to 1 kHz evoked higher torque, while carrier frequencies between 2.5 and 5 kHz resulted in lower perceived discomfort. In addition, most studies showed that shorter burst duty cycles (10%–50%) induced higher evoked torque and lower perceived discomfort. Methodological quality scores ranged from 5 to 8 on the PEDro scale. We conclude that Kilohertz-frequency alternating current develops greater evoked torque for carrier frequencies between 1 and 2.5 kHz and burst duty cycles less than 50%. Lower perceived discomfort was generated using Kilohertz-frequency alternating currents between 2.5 and 5 kHz and burst duty cycles less than 50%. Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.