The discipline of Three-Day-Eventing has recently undergone fundamental changes to the competition format. Traditionally, the second day of competition comprised an endurance test of roads and tracks exercise, a steeplechase and finally a cross-country course. Considering the temperature and humidity of competitions in countries hosting international competitions, many 3DE have excluded the roads and tracks and steepchase phases in order to minimise any adverse effects that fatigue may cause during the cross-country test, namely the horse falling. However, the effect of fatigue upon the jump stride has not been scientifically quantified.  

Lizzie Rapkin, a BSc Equine Science student at Aberystwyth University tested the effect of an endurance exercise on the ability of a horse to jump by measuring specific parameters of the take-off stride. The majority of the jumping power is generated by the hind quarters and during fatigue a subsequent reduction in power generated, would lead to the horse ‘crouching’ less onto its hocks. The hypothesis tested that following an endurance test the hock angle would be less acute compared to the angle generated by the same horse when it had not undergone endurance exercise.

Ten horses of mixed breed and ability were used in the experiment. The flexion or angle of the hock joint (tarsal flexion) were measured under two conditions, which were held two weeks apart. Under condition one, horses were warmed up for 15 minutes, then jumped a cross-country course; under condition two, horses were ridden over a roads, tracks and steeplechase before completing the same cross-country course. The horses were marked up with skin markers placed above specific limb joints and video recorded jumping the first and last fence of the cross-country course on both occasions. Lizzie collaborated with Russell Guire of Centaur Biomechanics, who kindly provided expertise, imaging equipment and Equinalysis software (pictured). The software is able to digitise the moving image of the hind limb enabling hock angle and stance duration parameters to be measured.

There was no significant difference for tarsal flexion immediately before take off. However there was a significant difference for tarsal flexion at the beginning of the stance phase at take off between the first (143.5°) and last jump (148.3°) when roads, tracks and steeplechase were included.

The results indicate that fatigue may cause the horse to be ‘less onto its hocks’ at take off, resulting in reduced jumping power. Further research is needed to gauge the effects of fatigue on tarsal flexion at take off at more elite levels. This research may provide valuable information as to whether the removal of the roads, tracks and steeplechase phases in the new format of eventing competitions is warranted.