ECSS Paris 2023: CP-MH22
INTRODUCTION: Head acceleration events (HAE) occur frequently in contact sports, particularly rugby union. Repetitive HAEs are associated with an increased risk of injury (World Rugby, 2023) and concussion (Stemper et al., 2022). Therefore, World Rugby recommends individualized monitoring of HAEs using instrumented mouthguards (iMG). However, existing iMG-based studies have focused mainly on elite athletes. Even in studies of high school rugby players abroad, HAEs have typically been reported at the group level, with limited longitudinal individual-level data. High school rugby players are in a developmental stage and may be more susceptible to neurological effects compared with adult athletes (Patricios et al., 2023). This study aimed to use instrumented mouthguards (iMG) to describe HAEs over a three-month period in Japanese high school rugby players and to calculate individual HAE rates normalized to training and match playing time. METHODS: This study was conducted over a three-month period (from November 2025 to February 2026). Six high school male rugby players (age: 16.0 ± 0.0 years; height: 172.2 ± 4.9 cm; weight: 70.3 ± 4.8 kg) were prospectively monitored using iMG. A HAE was defined as a head impact exceeding 8 g of peak linear acceleration and was identified using a proprietary algorithm designed to exclude non-impact noise. Although peak angular acceleration was recorded by the device, it was treated as a reference value and was not included in the analyses. Athlete exposure (AE) was quantified as athlete-exposure minutes, where one AE was defined as one athlete participating in one minute of training or match play. HAE rates were calculated as the number of events per 100 AEs, representing the incidence of HAEs per 100 minutes of player participation. RESULTS: The mean total training participation time was 2220 ± 805 minutes, and the mean total match playing time was 98.3 ± 61.5 minutes. During training, the mean HAE rate was 6.1 ± 1.9 per 100 AEs. In contrast, match play demonstrated a higher mean HAE rate of 23.9 ± 9.3 per 100 AEs. No clinically diagnosed concussions occurred. However, one high-magnitude HAE occurring during training (90 g peak linear acceleration, 4514 rad/s² peak angular acceleration) exceeded thresholds used for Head Injury Assessment in professional rugby. This event occurred during a breakdown, with suspected contact between the player’s jaw and an opponent’s shoulder. CONCLUSION: This study provides preliminary data describing individual HAE rates in Japanese high school rugby players. HAE rates differed markedly between training and matches, with greater inter-individual variability observed during match play.
Read CV Yuta NakagawaECSS Paris 2023: CP-MH22
INTRODUCTION: Inter-limb asymmetry is widely used in athlete monitoring and injury risk screening, particularly in relation to strength and balance. Infrared thermography has been proposed as a non-invasive method to detect physiological asymmetries potentially associated with tissue stress or injury risk. Although infrared thermography is increasingly used in sports settings, evidence regarding the physiological relevance of lower limb thermal asymmetry in elite athletes remains limited, particularly in relation to neuromuscular imbalance. Therefore, this study investigated the relationship between thermal and functional asymmetry in elite female volleyball players using a data-driven profiling approach. METHODS: Thirty elite female volleyball players (age: 18.47 ± 4.61 years; BMI: 20.66 ± 2.13 kg/m²; training experience: 8.40 ± 5.64 years) participated. Bilateral thermography (FLIR E6 Pro) was performed for the anterior thigh, posterior thigh, and posterior calf regions. Thermal asymmetry was defined as the absolute side-to-side temperature difference. A global thermal asymmetry score was calculated as the mean of the three regions (0.27 ± 0.19°C). Twelve athletes (40%) showed ≥0.5°C asymmetry in at least one region, consistent with previously suggested clinical thresholds. Neuromuscular assessment included isometric quadriceps and hamstring strength (handheld dynamometry), vertical jump, single-leg hop distance, Y-Balance composite reach score, static single-leg balance, and joint position sense. Movement quality was assessed using the Functional Movement Screen (FMS), with scores ≤14 indicating increased injury risk. Functional asymmetry indices were calculated for each parameter and standardized to derive a global functional asymmetry score. Associations were examined using Spearman correlation. K-means clustering based on z-standardized thermal and functional asymmetry variables identified asymmetry profiles. Between-cluster differences were analyzed using Mann–Whitney U tests. Statistical analyses were performed using SPSS 24.0. RESULTS: No significant association was found between global thermal asymmetry and global functional asymmetry (ρ = −0.047, p = 0.805). Cluster analysis identified two profiles (n = 26 and n = 4). The smaller cluster demonstrated consistently elevated thermal asymmetry. This subgroup showed significantly lower FMS scores (p < 0.001), with a greater proportion scoring ≤14, and reduced static balance performance (p = 0.011). Dynamic asymmetry measures did not differ between clusters. CONCLUSION: Thermal asymmetry was not linearly associated with neuromuscular asymmetry in this cohort. However, profiling revealed a small subgroup characterized by elevated thermal asymmetry and poorer movement quality. Thermal asymmetry may not serve as a continuous marker of functional imbalance but could contribute to identifying specific risk-related profiles within multidimensional athlete monitoring. Larger studies are needed to clarify its role in elite populations.
Read CV Begüm Kara KayaECSS Paris 2023: CP-MH22