Quantitative modeling reveals prolonged lactate clearance in young and unraced Jeju horses following high-intensity exercise under passive recovery conditions

Objective To model lactate recovery kinetics in relation to sex, age, running speed, and racing experience, and to estimate blood lactate clearance time under passive recovery conditions that reflect current management practices in Jeju horses, a less well-characterized pony-sized indigenous breed. Methods From October through December 2022, BLC was measured at baseline, 10 minutes after 800-m barrier trials (time [T]-1), and 50 minutes (T2) after 800-m barrier trials in 40 race-trained Jeju horses (2 to 4 years old). Lactate clearance was modeled using nonlinear regression with an exponential decay function. Results Mean BLC values were 1.13 ± 0.94 (baseline), 19.75 ± 2.27 (T1), and 7.71 ± 3.44 mmol/L (T2). At T2, BLC was significantly higher in 2-year-olds and unraced horses but not between sexes, between the 3- and 4-year-old groups, or across qualifying running speeds (≥ 11 and < 11 m/s). The lactate clearance model, BLC (mmol/L) = 1.13 + 24.18 X e −0.03XT , predicts that BLC falls below 2 mmol/L in 110 minutes under passive recovery. Conclusions Lactate clearance was slower in younger and unraced horses, highlighting the importance of training-induced adaptations. As this study was conducted under passive recovery conditions, the results offer a reference point for Jeju horses currently managed without active recovery and underscore the need for structured protocols to further optimize recovery strategies after exercise. Clinical Relevance This study provides foundational data on postexercise lactate clearance in Jeju horses and highlights the potential benefits of incorporating active recovery into training practices.