Reasons for performing study: Fitness assessment can be challenging. The use of global positioning systems (GPS) with heart rate (HR) monitors has been promising; however, evaluation of speed parameters during training has not been reported.
Objectives: To evaluate speed indices during training in Thoroughbreds using a GPS-HR monitor.
Methods: Thoroughbreds (n = 102) were assessed during training with data collected each work day (WD; sprinting). Speed indices evaluated included maximal velocity (Vmax), duration at Vmax (Vmaxt), acceleration rate (m/s2) from 800 m to Vmax (Acc800-Vmax), the distance (m) 6 (VmaxD6) and 12 (VmaxD12) s before (acceleration [a]) and after (deceleration [d]) Vmax and the deceleration rate from Vmax to the finish (VmaxDFd). Blood for plasma lactate ([LA]) and creatine kinase ([CK]) measurements were taken before (T0), 5 mins (T1) and 6 h after exercise (T2). WD accumulation, jockey, gallop condition, horse gender, age, total distance covered (DistT), maximum HR (HRmax), velocity at 200 beats/min (V200) and velocity at maximum HR (VHRmax) for each WD were evaluated for associations with [LA], [CK], speed indices and racing performance. Data were analysed by repeated measures ANOVA with P<0.05 significant.
Results: No speed parameter clearly changed with training. Gallop condition affected Vmax, Vmaxt and all distances covered with Vmax and distances increasing and Vmaxt decreasing as gallop surface became firmer. Jockey influenced Vmax, VmaxD6a and all decelerations, while DistT was inversely associated with Acc800-Vmax, HRmax and V200 and positively associated with Vmax, all accelerations and decelerations. [LA] at T1 was positively associated with DistT and VmaxDFd.
Conclusions: Speed parameters did not change with training but were affected by jockey, gallop condition and exercise distance. This information may help to modify training to maximise fitness, minimise injury and choose distances best suited for individuals.