The progression values of heart rate and biochemical plasma parameters during training of 3-years old warmblood stallions for breeding licensing.

Overview

• This study investigated how 3-year-old Czech Warmblood stallions physiologically and biochemically adapt to both acute exercise and a 112-day long training program designed for breeding licensing.
• The research measured heart rate and various blood plasma parameters to assess cardiovascular responses and biochemical changes during free jumping exercises, aiming to understand training effects on young sport horses.

Introduction and Objectives

• Physiological adaptations in young sport horses undergoing standardized training for breeding purposes are not fully understood.
• The study focused on cardiovascular and biochemical plasma responses to both short-term (acute) exercise and long-term training in Czech Warmblood stallions aged three years.
• The exercise chosen was standardized free jumping, a relevant activity in the context of breeding licensing.

Methods

• Thirteen Czech Warmblood stallions participated in a 112-day training regimen specifically tailored for breeding licensing preparations.
• Heart rate (HR) was continuously monitored during standardized free jumping tests, capturing minimum, maximum, and average values to evaluate cardiovascular response.
• Blood samples were taken to analyze plasma biochemical parameters at rest, 15 minutes post-exercise, and 60 minutes post-exercise to observe acute and long-term biochemical changes.

Results: Acute Exercise Effects

• Heart rate parameters and plasma lactate levels remained stable over the entire study, indicating the exercise intensity remained within an aerobic range suitable for training.
• Acute exercise caused significant but transient changes in several plasma markers 15 minutes post-exercise:
• Total protein and albumin levels showed shifts, reflecting immediate physiological responses to exercise.
• Cortisol peaked at 83.87 ± 3.59 nmol/L, indicating an acute stress and energy mobilization response.
• NEFA (non-esterified fatty acids) increased transiently to 0.13 ± 0.01 mmol/L, reflecting mobilization of fat stores for energy.

Results: Long-term Training Adaptations

• Several plasma biomarkers demonstrated clear trends over the 112-day training period, highlighting physiological adaptations:
• Total Antioxidant Status (TAS) increased linearly (correlation R=0.958, p<0.001), suggesting enhanced antioxidant defense with training.
• Post-exercise Lactate Dehydrogenase (LDH)</strong decreased linearly (R=0.958, p<0.001), indicating improved muscle metabolism and possibly reduced muscle strain.
• NEFA and bilirubin levels post-exercise also decreased linearly (NEFA R=0.754; bilirubin R=0.930), implying more efficient energy use and liver function over time.
• Markers related to musculoskeletal remodeling, such as Alkaline Phosphatase (ALP) and resting Creatine Kinase (CK), followed inverted U-shaped patterns (ALP R>0.97, CK R²=0.904), representing a peak in tissue adaptation mid-training.
• Creatinine and urea displayed U-shaped trends (R ≈ 1.0), likely reflecting adaptive changes in kidney function and fluid balance as training progressed.
• No indicators of muscle damage or chronic stress were found during the study, affirming the training protocol’s appropriateness for the horses’ welfare.