Author(s): KARA KAYA, B., KILIÇ, B.B., ÜSTÜN, Ç., DURGUN, B.C., Institution: BIRUNI UNIVERSITY, Country: TURKEY, Abstract-ID: 1890

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.