Cardiac morphologic changes induced by a 10-week water treadmill training for show jumping horses: A preliminary evaluation.

Overview

• This study investigated how a 10-week water treadmill training program affected the heart structure, function, and energy expenditure of trained show jumping horses.
• The researchers measured various cardiac parameters before and after training, along with performance and metabolic markers during a show jumping field test.

Study Purpose and Design

• The main aim was to evaluate cardiac adaptations and energy demands in jumping horses subjected to a specific water treadmill (WT) training regimen.
• Six trained show jumping horses participated in the study.
• The water treadmill training lasted 10 weeks, with sessions twice a week, each lasting 20 minutes, and water level maintained at carpus (knee) height.
• Measurements were taken before training (PRETR) and after training (TR) to assess the effects of the WT program.

Cardiac Assessments

• Transthoracic echocardiography was used to measure structural heart parameters using a phased array transducer operating between 1.9-4 MHz.
• Parameters measured included interventricular septal thickness (IVS), left ventricular internal diameter (LVID), and posterior wall thickness (LVPW) during both end-diastole (d) and systole (s).
• Heart rate (HR) was recorded.
• Derived cardiac function indices calculated were:
  • Left ventricle end diastolic volume (Vd)
  • Left ventricle end systolic volume (Vs)
  • Fractional shortening (FS%) – an indicator of cardiac contractility
  • Ejection fraction (EF%) – percentage of blood pumped out of the ventricle with each beat
  • Stroke volume (SV) – volume of blood pumped per heartbeat
  • Cardiac output (CO) – total blood volume pumped per minute

Performance and Metabolic Testing

• After training, horses performed a show jumping field test (SJT) with heart rate monitored throughout.
• Energy expenditure (EE), cost of transport (COT), and metabolic power (Pmet) were calculated from HR data to assess efficiency.
• Blood samples were taken before and 240 minutes after recovery to assess cardiac troponin I (cTnI), a marker of cardiac muscle stress or injury.

Key Findings

• Structural Cardiac Changes:
  • Significant increase in interventricular septal thickness at end diastole (IVSd): approx. 2.56 cm to 2.79 cm.
  • Posterior wall thickness at end systole (LVPWs) increased from about 4.21 cm to 4.48 cm.
  • Significant decrease in left ventricle internal diameter at end systole (LVIDs): from approx. 5.99 cm to 5.68 cm, suggesting thicker walls relative to chamber size.
• Functional Cardiac Improvements:
  • Ejection fraction (EF%) increased from ~75.0% to ~78.6%, indicating improved pumping efficiency.
  • Fractional shortening (FS%) improved from ~46.8% to 50.2%, reflecting enhanced contractility.
  • Cardiac output (CO) rose significantly from about 16.7 L/min to 21.3 L/min.
  • Resting heart rate increased from around 31.2 bpm to 36.3 bpm post-training.
• Cardiac Biomarkers:
  • Significant reduction in cardiac troponin I (cTnI) levels, suggesting reduced myocardial stress or damage after training.
• Energy Metabolism and Performance:
  • Energy expenditure (EE) during the show jumping test improved markedly: reduced from 1000.3 to 573.5 J/kg/min, indicating better energy efficiency.
  • Cost of transport (COT) decreased from 0.428 to 0.237 beats/kg/m (scaled by 10), also supporting improved efficiency.
  • Horses were able to reach higher speeds during the field test after training (from 12.9 km/h to 17.0 km/h).

Conclusions and Implications

• The 10-week WT training induced positive morphological changes in the cardiac muscle of show jumping horses, evidenced by increased wall thickness and improved contractility.
• Enhanced cardiac function was demonstrated by improved ejection fraction, fractional shortening, and greater cardiac output post-training.
• Improved cardiac efficiency and reduced cardiac stress (lower cTnI) suggest that water treadmill exercise benefits myocardial health.
• The energy usage during exercise was reduced, and horses showed improved physical performance, being able to jump faster and expend less energy for the same tasks.
• Overall, including water treadmill training in the routine conditioning of show jumping horses may improve cardiac health and athletic efficiency, potentially enhancing performance and longevity.
• These results are preliminary and should be validated with larger samples and longer-term studies.