Abstract: REASONS FOR PERFORMING THE STUDY: As there are no reports on the real workload of horses that jump fences, this study was undertaken in riding-school horses. OBJECTIVE: To compare the workload of horses jumping a course of fences with that of horses cantering over the same course at the same average speed without jumping fences. The workload variables included heart rate (HR), packed cell volume (PCV), acid-base balance (venous pH, pCO2, HCO3-) and blood lactate (LA), glucose, total protein and electrolyte concentrations. METHODS: Eight healthy riding-school horses performed test A (a course of approximately 700 m with 12 jumps from 0.8-1.0 m high at an average speed of approximately 350 m/min) and test B (same course at the same speed, but without the rails) in a crossover study with at least 4 h between the 2 tests. Before each test the horses were fitted with a heart rate meter (Polar Electro). Blood samples were taken from the jugular vein at rest prior to the test, after warm-up before starting the course, immediately after the course and after recovery. All samples were analysed immediately. RESULTS: The mean +/- s.d maximal HR (beats/min) during the course (184 +/- 17 and 156 +/- 21, respectively) and the mean HR after recovery (75 +/- 6 and 63 +/- 7, respectively) were significantly higher in test A compared to test B (P = 0.001 and P = 0.007 respectively). The mean LA concentrations after the course and after recovery (mmol/l) were significantly higher in test A (3.6 +/- 2.7 and 1.0 +/- 0.9, respectively) compared to test B (0.9 +/- 0.5 and 0.3 +/- 0.1, respectively), (P = 0.016 and P = 0.048 respectively). The mean PCV (I/l) after the course and after recovery was also significantly different between tests A (0.48 +/- 0.04 and 0.39 +/- 0.03, respectively) and B (0.42 +/- 0.04 and 0.36 +/- 0.03, respectively) (P<0.01). The mean pH and the mean HCO3- (mmol/l) after the course were significantly lower in test A (7.40 +/- 0.04 and 28.9 +/- 1.4, respectively) compared to test B (7.45 +/- 0.03 and 30.4 +/- 2.3, respectively) (P<0.05). CONCLUSIONS: This study indicates that in riding-school horses jumping fences, even at a low level competition, provokes a significant workload compared to cantering the same distance and speed without fences. POTENTIAL RELEVANCE: This study makes it clear that the extra workload of jumping fences should be taken into account in the training programmes of jumping horses. Further research with more experienced horses jumping higher fences will reveal the workload for top-level jumping horses.

Abstract: REASONS FOR PERFORMING STUDY: Endurance training induces changes in autonomic nervous system functions. High intensity training includes the risk of overtraining, in man and horse. Heart rate variability (HRV) is a noninvasive measurement of the autonomic regulation of the heart rate, which is quick and easy to measure with modern telemetric technology. HYPOTHESIS: Since HRV is affected by changes in the autonomic nervous system, it might be an early stage indicator of poor recovery from a previous bout of exercise or overreaching or overtraining in horses in general. METHODS: The aim of the study was to monitor recovery and the possible overtraining status in horses by measuring HRV. The measurements reflected the responses of the previous day activities during different training periods including basic training, precompetition and competition during a one-year follow-up. RESULTS: HRV was at the highest during precompetition period (P<0.05) and it decreased significantly during competition period (P<0.05), indicating an increased stress load in the competition period. Walking increased HRV significantly compared to complete rest or jogging as previous day activities during basic training and precompetition periods (P<0.05). This finding suggests that horses are more relaxed during moderate exercise than standing still or anaerobic exercise. CONCLUSIONS: HRV can be used to monitor the cardiovascular responses to training in horses but confirmatory measures may also be required in addition to HRV to exclude other possible causes of underperformance.

Abstract: REASONS FOR PERFORMING STUDY: Heart rate (HR) recovery immediately after exercise is controlled by autonomic functions and the time constant (T) calculated from HR recovery is thought to be an index of parasympathetic activity in man. OBJECTIVES: To investigate whether it is possible to evaluate autonomic function using the time constant in horses. METHODS: Five Thoroughbred horses were subjected to a standard exercise test. Following pre-medication with saline, atropine and/or propranolol, the horses ran for 2.5 min at a speed of 8 m/sec at a 10% incline and T was calculated from HR after the exercise. Secondly, 7 Thoroughbred horses were then trained for 11 weeks and T and maximal oxygen uptake (VO2max) measured at intervals of 1 or 2 weeks. In 6 horses, T with atropine pre-medication was also measured before and after the whole training period. Furthermore, the HR variability at rest was evaluated by power spectral analysis at intervals of 3 or 4 weeks. RESULTS: Time constant was increased by atropine and/or propranolol pre-medication, decreased with the progress of training and inversely correlated with VO2max during training (r = 0.43, P<0.005). Parasympathetic blockade significantly decreased T only after and not before, the training; however, T was lower in post training than in pretraining, irrespective of parasympathetic blockade. On the other hand, parasympathetic activity at rest was attenuated and sympathetic activity became predominant following the training. CONCLUSION: Heart rate recovery is affected by sympathetic withdrawal and parasympathetic reactivation in horses and suggests that physical training hastened HR recovery by improving the parasympathetic function after exercise with aerobic capacity. However, the effects of other factors need to be considered because the training effect appeared on T even under parasympathetic blockade. The parasympathetic activity at rest is in contrast to that after exercise, suggesting that T does not reflect parasympathetic activity at rest. POTENTIAL RELEVANCE: If demonstrated how HR recovery is controlled after exercise, its analysis will be important in the evaluation of physical fitness in horses.

Abstract: REASONS FOR PERFORMING STUDY: Running ability of Thoroughbred racehorses is correlated with maximal oxygen uptake, and the velocity at maximal oxygen uptake is highly correlated with the velocity at maximal heart rate (VHRmax). OBJECTIVE: To investigate the relationship between VHRmax and racing performance, expressed as 'peak dollars earned per race start'. METHODS: Heart rate (HR) and velocity were recorded in 25 Thoroughbred racehorses during trotting and subsequent fast gallops in the field at velocities of 15-16 m/sec. Velocity was recorded by a global positioning system (GPS). Maximal HR (HRmax) and maximal velocity (Vmax) were identified, and a linear regression of HR on velocity for trotting and galloping data was constructed to derive VHRmax. Horses followed the training programme designed by one trainer, had at least 6 race starts and were clinically sound at the time of testing. Race earnings were expressed as the peak dollars per start in the horse's race career. Data were normalised using the results for the square root of 'peak dollars earned per race start' and the significance of associations between variables was determined by correlation coefficient and least square analyses. RESULTS: Horses with higher VHRmax earned significantly more dollars per race start (r = 0.41, P<0.05), and horses with VHRmax less than 14.5 m/sec had mean earnings of less than A$2500 per race. There were no correlations between race earnings and either HRmax or Vmax. CONCLUSION: Field studies of the relationship between HR and velocity with a GPS enable identification of horses with limited earnings. POTENTIAL RELEVANCE: This study demonstrates that a field test of fitness of Thoroughbred racehorses that correlates with retrospective racing ability is feasible. The technique has potential application in commercial training environments assisting with decisions concerning racing careers of individual racehorses.

Abstract: REASONS FOR PERFORMING STUDY: Training is an important variable for determining athletic success. Nonetheless, there has been minimal scientific evaluation of racehorse training programmes. Training of racehorses focuses on running the horses at certain speeds using a combination of a stopwatch and rider's 'feel' for a horse's work intensity. Consequently, actual work intensity for individual horses is not clearly defined. OBJECTIVES: To 1) utilise a combined global positioning system (GPS) and heart rate monitor system to quantify training intensity and physiological responses of a group of racehorses undergoing training and racing; and 2) compare the workload measured by the GPS to that timed and recorded daily by a racehorse trainer. METHODS: Nineteen racehorses age 3 years were followed through a traditional training and racing programme over a 4 month period. Daily GPS and heart rate data together with the trainer's timing and distance data were collected while the horses were trained. Data were analysed using an ANOVA for repeated measures. RESULTS: The combined GPS/heart rate monitoring system detected different heart rate responses in individual horses subjected to the same training workouts. The average speeds detected with the GPS system were in agreement with average speeds timed by the trainer. However, peak speeds reached during training were significantly greater (P<0.05) than those estimated with stopwatch timing. The horses average training speeds increased significantly over the duration of the training period. CONCLUSIONS AND POTENTIAL RELEVANCE: The results from this study show that a GPS/heart rate monitor system provides a reliable measure of daily workload in horses during training. This technology provides a detailed picture of horses' training sessions and has the potential to provide a greater insight into the types of training that may predispose horses to injury.