Many show horses have events every weekend, and this includes jumping horses. Because of this frequency, the veterinarians at the University of Messina in Italy were concerned that jumping horses may not be rested and recovered after just a few days of rest when they compete every weekend, so they designed a study to analyze the issue. The physical stress of athletic competition causes metabolic changes in muscle enzymes, and increased muscle enzymes indicate that muscle damage has occurred. Now, this is not abnormal for equine athletes but it is a good idea to allow the muscle to heal before causing more damage.
In this study, the researchers investigated muscle enzyme levels in 12 jumping horses by taking blood samples before and after jumping competitions 2 weeks in a row. They found that metabolic changes indicate muscle fatigue. The metabolic changes were more significant after the second competition, suggesting the muscles suffer from excessive stress especially in the second weekend competition in a row. The authors indicate the short recovery period of only 5 days, from Sunday to Friday, could increase the possibility of muscle damage, and a longer recovery period is recommended to decrease the chance of damage.
Now lots of folks might believe that training at home would produce just as much physical stress as a competition itself but according to the researchers that is incorrect. Although training may be longer, the intensity of training is less than in competition. This study was performed on jumping horses, and the authors state you cannot consider these results to be necessarily accurate for other performance horses.