Introduction
Asymmetry of the trot may occur or increase during endurance rides due to lameness, pain or fatigue. By visual inspection of the movement it is difficult for veterinarians, riders and researchers to distinguish between fatigue and low‐grade lameness, which make objective movement analysis relevant for this purpose. The aim of this study was to determine changes in movement symmetry during long‐term exercise.
Methods
Movement symmetry of 45 horses finishing endurance rides of 120–160 kilometres was determined by tri‐axial accelerometry according to an earlier published method. Data was collected in Denmark and Germany from 5 international competitions between 2011 and 2013. Movement was assessed at trot on a straight‐line in‐hand on the day before the race and 30 mins to 3 hrs after passing the final veterinary examination. An overall symmetry index S was calculated on the basis of trunk accelerations measured at 240 Hz during 8 strides. All trotting sequences were recorded on videotape. A paired t‐test was performed comparing symmetry indices before and after racing for each individual horse.
Results
A significant decrease in post‐ride symmetry was detected (P = 0.0042). This is seen as a lower S‐index before racing (‐6.18; SD = 0.86. CI [‐6.427; −5.923]) compared to after racing (‐5.67; SD = 0.79; CI [‐5.908; −5.434]).
Conclusions
This study indicates that the biomechanical method applied allows quantification of the symmetry of movement during field conditions. Most horses had decreased movement symmetry after the race. Accordingly the study provides the basis for further investigation of the causes, including surface, climate and fitness; and the possible health consequences of asymmetric movement developed during long‐term exercise.
Ethical Animal Research
The study was pre‐approved by the FEI, the local organizing committees, ground jury, and Danish riding association (DRF). Participation was voluntary and the owner or rider signed an informed consent. All information regarding the horses is kept confidential and the horses coded for anonymity. Sources of funding: This study is part of a university and government funded PhD project. Private funding from “Hesteafgiftsfonden” and KDH (Royal Danish Horse Insurance). Competing interests: none.