International Journal of Human Movement and Sports Sciences 11(4): 886-892, 2023 http://www.hrpub.org DOI: 10.13189/saj.2023.110424 Recruitment of the Motor Units of Karatekas' Muscles during the Kick Performance Lyubomyr Vovkanych 1 , Bogdan Kindzer 2 , Mariia Fedkiv 3 , Dariush Skalski 2,4 , Paulina Kreft 2,4 , Igor Grygus 5,* , Volodymyr Starikov 6 1 Department of Anatomy and Physiology, Ivan Boberskyj Lviv State University of Physical Culture, Ukraine 2 Department of Fencing, Boxing and National Martial Arts, Ivan Bobersky Lviv State University of Physical Culture, Ukraine 3 Department of Human and Animals Physiology, Ivan Franko National University of Lviv, Ukraine 4 Department of Swimming and Water Rescue, Academy of Physical Education and Sport in Gdansk, Poland 5 Department of Physiotherapy & Occupational Therapy, Institute of Health, National University of Water and Environmental Engineering, Ukraine 6 Department of Physical Education, National University of Water and Environmental Engineering, Ukraine Received March 19, 2023; Revised June 12, 2023; Accepted July 19, 2023 Cite This Paper in the Following Citation Styles (a): [1] Lyubomyr Vovkanych, Bogdan Kindzer, Mariia Fedkiv, Dariush Skalski, Paulina Kreft, Igor Grygus, Volodymyr Starikov , "Recruitment of the Motor Units of Karatekas' Muscles during the Kick Performance," International Journal of Human Movement and Sports Sciences, Vol. 11, No. 4, pp. 886 - 892, 2023. DOI: 10.13189/saj.2023.110424. (b): Lyubomyr Vovkanych, Bogdan Kindzer, Mariia Fedkiv, Dariush Skalski, Paulina Kreft, Igor Grygus, Volodymyr Starikov (2023). Recruitment of the Motor Units of Karatekas' Muscles during the Kick Performance. International Journal of Human Movement and Sports Sciences, 11(4), 886 - 892. DOI: 10.13189/saj.2023.110424. Copyright©2023 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract The aim of our study was to reveal the relative contribution of the main types of motor units of the low extremities to the front kick performance by karate athletes based on surface electromyogram analysis. Our study involved 11 high-skilled karatekas (I Dan), aged 18–21 years, with training experience of 12–15 years. A surface electromyogram was recorded during the Mae Geri kick from Zenkutsu dachi stance. The electrical activity of the following right (dext.) and left (sin.) muscles was recorded: m. gluteus maximus, m. rectus femoris, m. biceps femoris, m. semitendinosus, m. gastrocnemius (caput lateralis), and m. tibialis anterior. It was found that during 57.6%–83.8% of the kick duration, the electrical activity of the different muscles was below 15% of the maximum. This indicates the activation of slow or low-threshold motor units. The largest percentage of the time of low activity was found for m. gluteus maximus sin., and the shortest one – for m. tibialis anterior. The period of the electrical activity of the muscles at the level of 20–30% from the maximum for different muscles ranged from 10.4% (m. gluteus maximus dext.) to 20.1% (m. tibialis anterior dext.), at the higher level of 35-45% from the maximum, it was shorter – up to 4.2–11.4%. Only for the 1.6% –17.9% of the total time of the kick, the level of electromyogram amplitude exceeded 50% of the maximal level, which indicates a relatively short period of activation of large motor units. The longest period of high electrical activity (50% and more of maximum) was found for m. tibialis anterior sin. (17.9%) and m. gastrocnemius (caput lateralis) dext. (16.9%). In these muscles, the longest period of fast, high-threshold, motor units activity was revealed. The tendency of increasing the periods of high electrical activity of the legs’ muscles of karatekas during kicks in the proximal-distal direction has been shown. Keywords Kyokushin Karate, Mae Geri, Zenkutsu Dachi, Surface Electromyogram 1. Introduction Today, the literature contains a number of publications devoted to the biomechanical and electromyographic analysis of kicking movements in karate. Kicks that have been analysed include Mae Geri [1, 2], Mawashi Geri [3],