ORIGINAL RESEARCH article
Front. Bioeng. Biotechnol.
Sec. Biomechanics
This article is part of the Research TopicRevolutionizing sports science: Biomechanical models, wearable tech, and AIView all 16 articles
Asymmetry of muscle co-activation during the two-armed kettlebell swing: insights into neuromuscular stability
Provisionally accepted
- 1Qassim University, Buraydah, Saudi Arabia
- 2Alexandria University, Alexandria, Egypt
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Abstract Introduction: Bilateral asymmetry reflects strength or functional differences between dominant and non-dominant limbs, which can influence performance. Investigating asymmetry and muscle co-activation during the two-armed kettlebell swing may clarify its role in performance enhancement and injury risk. This study specifically examined co-activation and asymmetry in shoulder and trunk muscles during the exercise. Method: Twenty-four participants (age: 23.9 ± 2.5 years; body mass: 82.8 ± 8.0 kg; height: 177.8 ± 6.5 cm) were included in the study. Surface electromyography signals were recorded using a wireless EMG system and data were collected bilaterally from twelve muscles (six muscles per side: anterior deltoid, posterior deltoid, erector spinae longissimus, erector spinae iliocostalis, external oblique, and rectus abdominis). Each participant completed two trials of the two-armed kettlebell swing, with at least five repetitions. Results: The results showed that the shoulder co-activation index significantly increased on both sides during the float, drop, and deceleration phases (Right side: F = 35.12; p < 0.001; Left side: F = 69.80; p < 0.001). Additionally, co-activation between the erector spinae and rectus abdominis, as well as between the erector spinae and external oblique muscles, was highest during the float and drop phases (Right side: F = 165.1; p < 0.001; Left side: F = 100.08; p < 0.001). The findings revealed some asymmetry in muscle co-activation, particularly during the float phase (22.39%). However, overall asymmetrical levels remained low during the more mechanically demanding phases (propulsion, drop, and deceleration). This is a provisional file, not the final typeset article Conclusion: The study shows clear phase-dependent muscle activation patterns, with anterior deltoid and spinal extensors leading during propulsion, and greater posterior engagement and co-activation stabilizing the float, drop, and deceleration phases. A small asymmetry appeared mainly in the float phase, while the overall asymmetry index stayed low during the more demanding phases.
Keywords: bilateral symmetry, Injury risk assessment, Motion analysis, physical activity, strength training, wearable sensors
Received: 27 Jun 2025; Accepted: 10 Dec 2025.
Copyright: © 2025 Abuwarda, Alotaibi and Akl. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Khaled Abuwarda
Abdel-Rahman Akl
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