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High intensive intermittent exercise (HIIE) is used to condition horses for racing. A study was done to examine the effect of short duration HIIE on the maximal speed (Speedmax) and v4 of 6 Thoroughbred race horses (v4: speed at which under defined conditions the blood lactate concentration [LA] reaches 4mmol/l). Horses were exercised during 8 weeks with one HIIE session per week on a dirt track. A HIIE session consisted of two runs of 100m each at near maximal speed separated by 10 minutes walking. After every second week during the conditioning period (CP) the number of runs was increased by one finishing with 5 runs per HIIE session in the last two weeks of CP. Prior to the CP, horses performed a submaximal standardized exercise test (SETsubmaximal) and a maximal speed test (SETspeedmax) to determine their v4 and Speedmax respectively. SETsubmaximal was conducted every 2 weeks until the end of CP and SETspeedmax after 4 weeks and 8 weeks of CP. The v4 of horses declined during the first 4 weeks of CP (p < 0.05), but returned to initial levels thereafter. Speedmax remained equal over time. The results indicate that further studies need to be done to find optimal combinations of exercises to simultaneously increase Speedmax and v4 of horses. [ABSTRACT FROM AUTHOR]

Performance diagnosis of Standardbred racehorses needs to be improved. It was examined whether parameters derived of the blood plasma cortisol concentration (CORT) during a standardized exercise test (SET) used to determine the endurance parameter v4 (velocity run under defined conditions inducing 4mmol/L blood lactate concentration) provided additional information for performance diagnosis of two-, three-, and four-year-old Standardbred horses during a racing season. The CORT parameters were CORTstart (CORT after warm-up but before starting), CORTmax (maximal CORT) and CORTmax–min (difference between the CORTmax and CORTmin). The v4 of the horses was related to all CORT derived parameters and the effect of testing in April, June and August on the CORT derived parameters was examined for all age-groups. The date of testing did not influence CORT derived parameters in any age group (P>0.05 all). CORTmax−min of the four-year-old horses was the only CORT derived parameter showing a significant relationship with v4 (P=0.048; r2 = −0.27). None of the CORT derived parameters was different among age-groups. In conclusion, further studies need to be done to clarify whether the CORT parameters defined are useful for performance or poor performance diagnosis. [ABSTRACT FROM AUTHOR]

In endurance racing, horses are stopped several times during a race for a veterinary inspection at so-called vet gates and heart rate is the relevant factor for the decision to continue the race. The influence on resting heart rate (HRResting) of endurance racehorses of the following factors was examined: 1) variation by day; 2) morning and afternoon variation; 3) ambient temperature and relative humidity; 4) age and v4 (v4=speed at which the blood lactate concentration is 4mmol/L under the defined conditions); 5) the method used to determine HRResting: auscultation or heartrate meter (HRM). Methods: The HRResting of 19 horses conditioned for endurance racing was determined. They were exercised either in a field or on a treadmill. It was found that HRResting: 1) differed between days (P<0.001 in the treadmill group, P=0.047 in the field group); 2) was higher in the afternoon than in the morning in the field group only (P=0.001); 3) increased with higher ambient temperature (P=0.024) while relative humidity did not affect it; 4) was not related to the age or v4 of the horses; 5) measured by HRM was higher than by auscultation (P=0.001). In conclusion the determination of HRResting of a horse should be based on a mean value determined after measurements taken on several consecutive days under as far as possible standardised conditions. [ABSTRACT FROM AUTHOR]

The objective of this study was to describe the training and changes in biophysical variables of 2-, 3-, and 4-year-old Standardbred racehorses trained by a successful trainer during a racing season. Methods: The horses were regularly weighed and submitted to standardised exercise tests (SETs) to determine v4 (velocity run under defined conditions inducing 4 mmol/L blood lactate concentration). The training of the horses was protocolled and related to changes in v4. The effect of the age of horses on their v4 and body weight (BW) was analysed using ANOVA for repeated measures and on training parameters using an univariate ANOVA. The relationship between the changes in v4 and training parameters was examined by means of linear and exponential regressions. Results: The BW of the 3- and 4-year-old horses remained constant during the observation period, whereas it increased for the 2-year-olds (P = 0.0033). Overall, the v4 of the 2-year-olds increased during the racing season (P = 0.043), whereas it remained constant for the 3- and 4-year-olds. The only differences in the training parameters among the age groups were that the 3-year-olds were started more frequently than the 2- and 4-year-olds (P = 0.037), and 2-year-olds were more often exercised fast than the older horses (P = 0.029). The v4 changes between consecutive SETs were not attributable to training parameters. The conclusion of this study is that the data collected in a remarkably successful racing stable provides a basis to introduce changes to further optimise the training of Standardbreds. [ABSTRACT FROM AUTHOR]

Abstract: Intensive short intervals of exercise are used to condition horses for racing. In this study, the effect of exercising horses one, two, or three times a week during 6 weeks using two intervals with near-maximal speed over 100 m on v4 (speed at which, under defined conditions, the blood lactate concentration reaches 4 mmol/L) and muscle thickness (MT) of supraspinatus and extensor carpi radialis was examined. Thoroughbreds (4-5 years of age) were exercised twice at near-maximal speed over 100 m, separated by a 10-minute period at walk, on dirt track during conditioning periods (CP) of 6-week duration. This exercise was undertaken once (six horses), twice (six horses), or thrice (five horses) a week during a CP. Before, every 2 weeks during, and 2 weeks after the CP, horses were subjected to a standardized exercise test to determine their v4. Before and after CP, the MT of the extensor carpi radialis and the supraspinatus was examined by ultrasonography. There was no differential effect of the number of weekly exercises on v4. Pooling the data of all horses, a decrease of v4 was found. The decrease became evident after the sixth week of conditioning. MT did not change. The results indicate that the examined exercise protocols could negatively impact racing performance of horses. [Copyright &y& Elsevier]

Abstract: This study examined the effect of exercising horses 3 times per week with two bouts of 5-minutes'' duration at their v10. Six Thoroughbreds were treadmill-conditioned for 6 weeks. A standardized exercise test (SET) was performed at the beginning of the conditioning period to determine the blood lactate–running speed (BLRS) relation, and the SET was repeated every 2 weeks. After each SET, the BLRS relation was used to calculate the horse''s speed, which produced a blood lactate (LA) concentration of 10mmol/L (v10) and 4mmol/L (v4). Each horse was then conditioned for the next 2 weeks (3 times/week) at its individual v10 for two 5-minute bouts with a 5-minute walking phase in between. Exercise speed was individually adapted to the new v10 every 2 weeks. The v4 of horses decreased after the first 2 weeks (from 6.23±0.41m/s to 5.95±0.33m/s, mean±SD; P < .05), increased in the following 2 weeks (6.33±0.58m/s; P < .01), and stayed constant thereafter (P > .05). The conclusion drawn was that exercising horses 3 times per week at their v10 for two 5-minute bouts did not improve v4. [Copyright &y& Elsevier]