PSXII-1 Exploring the link between vertical acceleration and thermographic temperature variations in Peruvian Paso Horses: Implications for gait efficiency and performance.

Abstract The Peruvian Paso Horse (PPH) is a native Peruvian breed globally recognized for its distinctive isochronous, smooth lateral gait, a critical trait for both functional performance and selective breeding. Advances in biomechanics and infrared thermography provide objective methodologies to evaluate locomotor patterns and physiological stress markers, offering new insights into gait efficiency and muscular workload in equines. This study aimed to investigate the association between vertical acceleration during locomotion and thermographic temperature variations in the gluteal musculature of Peruvian Paso Horses. A total of 88 adult horses (males and females), aged 4 to 10 years, were analyzed. To ensure accurate thermographic assessment, each horse was positioned on level ground, maintaining a rectangular parallelogram stance in profile view, ensuring that each limb symmetrically overlapped the opposite limb before and after exercise. Kinematic data acquisition was performed using high-definition cameras (1920 × 1080 px, 60 fps), and vertical acceleration was quantified via video analysis using KINOVEA software, extracting data every 15 ms. A reference marker was placed on the croup, and the signal was processed with a Butterworth filter to calculate the root mean square (RMS) of vertical acceleration. Horses were evaluated at a “paso llano” gait, moving at speeds of 2.5–4 m/s over a 100-meter linear track. Infrared thermography was conducted using a FLIR thermal camera, capturing images of the gluteal muscle before and after exercise. Additionally, maximum temperature values were recorded to determine the peak thermographic variation in the dorsal region. Results indicated no significant correlation between gluteal temperature differences and vertical acceleration (r = -0.088, p > 0.05). However, a strong negative correlation (r = -0.344, p < 0.01) was observed between vertical acceleration and maximal thermographic temperature differentials in the dorsal musculature. This could indicate that the gluteal musculature functions more efficiently, with lower relative energy expenditure but enhanced heat dissipation, resulting in a greater post-exercise temperature difference. These findings underscore the potential of integrating biomechanical and thermographic analyses as novel selection criteria in breeding programs, contributing to enhanced locomotor efficiency, athletic performance, and equine welfare. This study provides a new physiological perspective on functional evaluation in PPH, offering quantitative markers for optimizing training, genetic selection, and management strategies. Future research should explore the long-term effects of locomotor dynamics on muscular adaptation and metabolic efficiency in elite Peruvian Paso Horses.