ORIGINAL RESEARCH article
Front. Neurol.
Sec. Neurotrauma
Volume 16 - 2025 | doi: 10.3389/fneur.2025.1603033
This article is part of the Research TopicIntegrative Approaches to Acute Brain Injury: Vascular, Electrical, and Metabolic InteractionsView all 4 articles
Assessment of the Brain Impact of Soccer Heading Using Pupillary Light Reflex
Provisionally accepted
Junzo Nakao1,2
Ai Muroi2*
Aiki Marushima2
Kuniharu Tasaki2Yoshiaki Inoue2Yuji Matsumaru2
Eiichi Ishikawa2- 1Osaka Medical and Pharmaceutical University, Takatsuki, Japan
- 2University of Tsukuba, Tsukuba, Ibaraki, Japan
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Background: Soccer heading is linked to adverse cognitive effects and changes similar to traumatic brain injury (TBI). In recent years, pupil light reflex (PLR) analysis via pupillometry offers a practical, reliable and objective neurological assessment for TBI. This is the first study to evaluate brain impact from soccer heading by evaluating PLR. We aimed to evaluate changes in PLR from heading and investigate if rubber balls reduce brain impacts compared with regular soccer balls.Methods: Our study involved 30 male healthy volunteer participants aged 18–29 years with >5 years of soccer experience. PLR was measured using the NPi-200 pupillometer system before and after performing every 10 headings, up to 30 headings with regular (session 1) and rubber soccer balls (session 2) in separate sessions. The parameters included neurological pupil index (NPi), constriction rate (CH), constriction velocity (CV), and maximum constriction velocity (MCV). Results: In session 1, CH and MCV significantly decreased compared with the baseline after 30 headings. In session 2, only CH significantly decreased compared with the baseline. CH significantly decreases from the 20th heading onwards in session 1 compared with session 2 (both at 20 and 30 headings; p < .001). CV significantly decreased after the 30 th heading in session 1 compared with session 2 (p = .038.) MCV significantly decreased at the 20 th (p = .037) and 30 th (p = .010) headings in session 1 compared with session 2. Conclusion: Heading affects PLR, with regular soccer balls causing more significant changes than rubber balls. The use of rubber balls during training may mitigate brain impacts, offering a safer alternative for players.
Keywords: brain impact, Heading, pupillary light reflex, Soccer, Traumatic Brain Injury
Received: 31 Mar 2025; Accepted: 07 May 2025.
Copyright: © 2025 Nakao, Muroi, Marushima, Tasaki, Inoue, Matsumaru and Ishikawa. 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: Ai Muroi, University of Tsukuba, Tsukuba, 305-8577, Ibaraki, Japan
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