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

This study aimed to investigate cardiac adaptations and energy expenditure of jumping horses after water treadmill (WT) training. Six trained horses were evaluated before (PRETR) and after (TR) a WT training (20 min, twice/week, water at carpus height) for 10 weeks. Transthoracic echocardiography was performed at PRETR and TR with phased array transducer (1.9-4 MHz) to obtain interventricular septal thickness (IVS), LV internal diameter (LVID), and posterior wall thickness (LVPW) at end-diastole (d) and systole (s) and heart rate (HR). Left ventricule end diastolic volume (Vd) and end systolic volume (Vs), fractional shortening (FS%), ejection fraction (EF%), stroke volume (SV) and cardiac output (CO) were calculated. Then, animals were performed a show jumping field test (SJT) using a HR monitor and energy expenditure (EE), cost of transport (COT) and metabolic power (Pmet) were calculated. Blood samples were obtained before and at 240 min of recovery for cardiac troponin analysis (cTnI). Data was analysed using paired t-test (p < 0.05). WT training led to significant increases of IVSd (∼2.56 vs. ∼2.79 cm; p = 0.001), LVPWs (∼4.21 vs. 4.48 cm; p = 0.032), EF% (∼75.0 vs. ∼78.6%; p = 0.049), FS% (∼46.8 vs. 50.2%; p = 0.048), CO (∼16.7 vs. ∼21.3 L/min; p = 0.015) and HR (31.2 vs. 36.3 bpm; p = 0.031); and a significant decrease of LVIDs (∼5.99 vs. 5.68 cm; p = 0.002) and cTnI levels. Significant improvements were observed for EE (1000.3 vs. 573.5 J/kg/min; p = 0.046) and COT (0.428 vs. 0.237 beats/kg/m x10³; p = 0.036), with animals reaching higher speeds (12.9 km/h vs. 17.0 km/h) after the training program. The inclusion of WT in the routine training of show jumping horses induced cardiac structural and functional adaptations, enhancing myocardial contractility and overall cardiac efficiency.