DURATION OF THE PROJECT:
1. 9. 2023 – 31. 8. 2025
LEAD PARTNER:
University of Primorska, Faculty of Health Sciences
POSTDOC RESEARCHER
Assist. Prof. Žiga Kozinc (SICRIS, ResearchGate)
Project Implementation:
The research project Z5-50181-2023: Establishing the Scientific Basis for Eccentric Quasi-Isometric Resistance Exercise was successfully completed at the Faculty of Health Sciences, University of Primorska. The project aimed to systematically investigate the biomechanical characteristics as well as the acute and mid-term effects of eccentric quasi-isometric (EQI) muscle actions, a training approach increasingly used in sport and rehabilitation practice but previously only sparsely examined in scientific literature.
The project included controlled experimental studies focusing on the knee and ankle joints. The research addressed the temporal structure of EQI contractions, torque development, mechanical impulse, fatigue responses, and comparisons with isokinetic and traditional eccentric loading protocols. Measurements were conducted using an isokinetic dynamometer, standardized mechanical assessment protocols, and ultrasound-based evaluation of the muscle–tendon unit.
The findings provided a more precise biomechanical characterization of EQI muscle actions and contributed to understanding their acute responses and adaptive effects compared to other forms of resistance exercise. Project results were published in international peer-reviewed journals indexed in WoS and Scopus and presented at scientific conferences. Several open-access publications have already received initial citations in the international research community.
The project also contributed substantially to postgraduate education, as it was directly linked to doctoral research training. The developed methodological approaches and research findings have been integrated into undergraduate and postgraduate teaching in the fields of kinesiology, biomechanics, and rehabilitation sciences.
Publications
Ličen, U., Oranchuk, D. J., & Kozinc, Ž. (2024). Exploring the biomechanics and fatigue patterns of eccentric quasi-isometric muscle actions in the knee extensors and flexors. European Journal of Applied Physiology, 124(11), 3409-3419.
Križaj, L., Šarabon, N., & Kozinc, Ž. (2025). Acute fatiguing effects and biomechanical characteristics of a single bout eccentric quasi-isometric resistance exercise of ankle plantar flexors. Frontiers in bioengineering and biotechnology, 13, 1517098.
Križaj, L., Kozinc, Ž., & Šarabon, N. (2025). Eccentric Quasi-Isometric Exercise Produces Greater Impulse with Less Pain than Isokinetic Heavy–Slow Resistance Exercise in Ankle Plantar Flexors: Quasi-Randomized Controlled Trial. Applied Sciences, 15(20), 11177.
Ličen, U., & Kozinc, Ž. (2024). Ekscentrične kvaziizometrične kontrakcije iztegovalk in upogibalk kolena-primerjava biomehanskih značilnosti ter utrujenosti med moškimi in ženskami. Revija Šport, 72.
Ličen, U., & Kozinc, Ž. (2025). Ekscentrično-kvazi-izometrična vadba: pregled raziskav o biomehanskih značilnosti in akutnih učinkih. Šport: revija za teoretična in praktična vprašanja športa, 73(1-2), 168-174.
Kozinc, Ž. (2025, July). Biomechanical, fatigue, and muscle damage responses to eccentric quasi-isometric contractions: Findings from multiple studies [Conference presentation]. ECSS Rimini 2025 – European College of Sport Science, Rimini, Italy.
Abstract
Lately, a novel exercise training method, termed eccentric-quasi-isometric training (EQI), has been gaining in popularity. isometric and eccentric exercise. The simplest way to describe EQI contractions is holding a position until isometric subsequent eccentric phase. The theoretical basis for the use of EQI is well established, and some short-term (e.g., less muscle soreness and lower impairment in neuromuscular performance) have been demonstrated. However, remain unexplored: what are the kinematic and kinetic characteristics of EQI multi-joint exercises? How do the term effects of EQI training compare to the effects of comparable eccentric training? This project will establish be used for further intervention research and practical application. Thus, the overarching purpose of this project objectives of this project are to a) assess the kinetic and kinematic characteristics of selected EQI exercises and long-term effects of EQI with comparable isometric and eccentric exercise protocols on muscle architecture, neuromuscular
participants’ subjective responses. Both single-joint open chain (e.g., knee flexion and extension) and close chain standing), as well as multi-joint (e.g. supported bent rowing), will be investigated. The project program includes and WP4 contain the main research activities, while WP1 and WP5 are dedicated to project management and dissemination research will be carried out in 3 phases (one WP each) to achieve the project objectives: in WP2, we will perform different EQI exercises with 1-3 participants, trying out different exercise variants); in WP3 we will assess biomechanical (measurements of temporal, kinematic and kinetic characteristics); in WP4 we will evaluate the effect of EQI training chronic effects of EQI, in comparison to a similar eccentric and isometric exercise protocol). The EQI training method different ages and fitness levels. EQI could be used with athletes to prevent and treat injuries. It could also be musculoskeletal injuries in the general population. Finally, EQI could be used to maintain physical function in older the foundation upon which these aspects will be addressed in the future.
»The authors acknowledge the project EQI-TRAIN Establishing scientific foundations for eccentric quasi-isometric resistance training was finacially supported by the Slovenian Research and Innovation Agency.«
