Equine Gastric Ulcer Syndrome (EGUS) is a worldwide disease described in different categories of animals. A causal relationship between exercise and EGUS has been suggested, attributed to stress as well as physiological changes in the position of abdominal organs, especially during trot and gallop. EGUS can influence athletic fitness, as has been described in various papers on racehorses. The aim of this work was to determine if gastric ulcer healing is associated with changes in selected fitness parameters (i.e., speed, heart rate during exercise and recovery, stride length and frequency) in 21 trained showjumping horses affected by gastric ulcers. Four animals were excluded for incomplete healing or loss to follow-up. In the remaining seventeen subjects, all healed completely, and fitness parameters were evaluated before and after healing of EGUS during a ridden exercise. The animals were equipped with a fitness tracker validated for use in horses while they performed both flat work and a small obstacle course. Results show that speed and stride length increased after healing, with no concurrent modification in maximal heart rate recorded during exercise and the heart rate recorded during recovery. The increase in speed and stride length is probably related to the disappearance of abdominal discomfort, already described in racehorses after healing of gastric ulcers.