Electrocardiography
Electrocardiogram was taken in all horses 1 hour before and 5 min after exercise as per standard base-apex lead system described byVerheyen et al. (2010) by using the four lead electrocardiogram (Contec ECG300G Vet). The following parameters in Lead II were recorded. P wave amplitude and duration, QRS duration, T wave amplitude and duration, PQ interval, QT interval and RR interval. Electrocardiograms were recorded at the speed 25mm/s with an amplitude voltage of 10mm/mV.