Effects of training sessions on Beta-endorphin, lactate and heart rate changes of sport horses before and after show jumping.

Β-endorphin, blood lactate and heart rate (HR) changes of sport horses are considered as markers of stress and welfare, training state and vegetative responses. The aim of this research was to investigate the effects of training sessions on circulating β-endorphin, blood lactate and HR changes in sport horses before and after show jumping and their correlations. No. 8 trained jumpers (6 geldings and 2 females, 7‐12 years old), performed in four consecutive training sessions before and after competition; the circuit design, intensity and duration of training sessions were the same before and after competitions. Blood samples were collected from the jugular vein, in basal conditions, before training sessions, and after training sessions. The HR was obtained before the blood sampling. Plasma β-endorphin concentrations were measured using a commercial radioimmunoassay kit (Peninsula Lab., Inc., Belmont, CA). Blood lactate concentrations were measured using Accusport tester. Β-endorphin, lactate and HR showed higher values after training sessions than basal values both before and after competition. Compared to basal values, β-endorphin (P<0.001), lactate (P<0.05) and HR (P<0.05) showed higher values after training sessions before competition; β-endorphin values showed no significant increase, while higher lactate (P<0.05) and HR (P<0.01) values after training sessions after competition were recorded; 2-way RM-ANOVA showed that fence height did not significantly affect β-endorphin, lactate and HR changes. No significant differences between basal values of β-endorphin, lactate and HR before and after competition were observed. No significant correlations among β-endorphin, blood lactate and HR, and between these variables and different fence heights were observed. The increase of β-endorphin after training sessions both before and after competition confirmed its involvement in stressful conditions with a high emotional content, in accordance with previous data reported after competitive, sub- and maximal exercise (1,2); in addition, this trend reflected the need for modulation of fatigue and pain perception even in trained horses, although independently of difficulty level. The absence of a significant correlation between β-endorphin changes and different fence heights confirms previous studies reported after show jumping competitions and after experimental show jumping (2). The highest lactate and HR values after the training sessions showed the effect of additional physical effort involved during the four consecutive training sessions observed before and after competition.