The aims of this study were to determine the degree of stress in younger and older jumping horses in terms of different intensity trainings as well as to determine the stress adaption ability of different horses’ categories after different trainings. The research was conducted on the Holstein stallions, breeding type Croatian sport horses that were bred and trained in the same conditions. Two groups of jumping horses have been included in the training: seven young ones at the age of four to five years old and seven older ones aged eight to nine years old. The training analysis has been conducted over the competition period of time over the same three repetitions in May, July and September. In those periods of time, the monitored training was the lunge, running track for horses and hurdle jumping in the parkour. The samples were taken and the measurements were conducted in the 60th, 30th and 15th minute before the training, then during (heart beat) and after the training; and in the 5th, 15th, 30th, 60th, 90th and 180th minute after the training. According to the determined average values of analysed parameters in all training sessions (lunging, running track and hurdle jumping in the parkour) and months (May, July and September) in young (inexperienced) and older (experienced) horses, there were no increase in the analysed parameters above the positive stress levels, without decreasing trends. In both groups of horses in the 30th minute, the number of heart beats per minute was down below 55 while the cortisol concentration in saliva was as in the beginning of the monitoring. Younger horses respond to the effort during the training with greater variation in the number of heart beat. Also, in the recovery phase of training they reduce the number of beats quicker. Observed was more pronounced in physically harder trainings. The analysed parameters in the saliva of young horses showed more pronounced decreasing and increasing trends induced by physical exertion during the training than the older horses. Also, the physical effort during the training reduces the cortisol values in the saliva in both groups of horses in the amount of 45% in younger, and 20% in the elder horses. The determined correlation coefficients between the analysed parameters before, during and after the training ranged from 0.19 to 0.67 as well as from -0.28 to -0.34. The younger jumping horses, within the limits of positive stress, had more fatigue responses to the training while the time of returning to the resting period was shorter. Older jumping horses have routinely had trainings with a reduced physiological reaction to the positive stress and fatigue, while the time of returning to the resting period was longer. Further research should determine the variability of the analysed parameters in jumping horses at the end of their sporting careers.