bluuebunny/crossref_metadata_2025 huggingface dataset:
Equine plasma β‐endorphin concentrations are affected by exercise intensity and time of day
Authors: MEHL M. L. , SARKAR D. K. , II H. C. SCHOTT , BROWN J. A. , SAMPSON SARAH N. , BAYLY W. M.
Published: June 2010

Eight mature mares were exercised for 20 min at 60% V̇O2max and to fatigue at 95% V̇O2max. Plasma β‐endorphin (EN) concentrations were determined before exercise, after a 10 min warm‐up, and at the end of each exercise test Mean ± s.e. β‐endorphin concentrations were significantly (P<.05) higher following work at 95% V̇O2max when compared to that at 60% V̇O2max (420.0 ± 102.7 vs. 269.9 ± 30.69 pg/ml). Pre‐exercise samples were collected between 1000 and 1500 h. In order to evaluate whether any cyclic changes in EN secretion effects may have influenced results, a subsequent study was completed using 12 horses to assess diurnal fluctuations in EN concentrations, by measuring EN concentration every 2 h for a 24 h period. There was no statistical difference in mean values at any time between 0800 and 2000 h. Whether individual differences in EN concentrations reflected varying degrees of stress associated with the exercise could not be determined. Any possible link between EN concentration and exercise stress in exercising horses awaits clarification.
Effect of inhaled β2 adrenoceptor agonist, albuterol sulphate, on performance of horses
Authors: BAILEY J. , COLAHAN P. , KUBILIS P. , PABL L.
Published: June 2010

This study was designed to test the hypothesis that a specific ß2 adrenergic receptor agonist, albuterol sulphate, when delivered by metered‐dose inhaler (MDI) would affect the performance of Thoroughbred horses during incremental exercise testing. Six conditioned Thoroughbred horses were randomly assigned to one of 2 treatment groups: Group 1 horses received placebo and Group 2 received albuterol. Each horse received both treatments in a crossover design with a 3 week interval between trials. Horses inspired albuterol (900 μg) or placebo over a 5 min period followed by an incremental, peak oxygen consumption (V̇O2peak) exercise test. Facial arterial blood gases (Pao2, Paco2), pHa, temperature, haemoximetry (O2Hb, COHb, MetHb, RHb) and electrolytes (Na+, K+, iCa2+, Cl−) were measured. Heart rate (HR), V̇O2peak, CO2 production (V̇CO2), plasma lactate, speed at failure, exercise duration, and urine levels of albuterol and metabolites (Alburine) were monitored. The Paratrend7 intravascular sensor provided continuous arterial blood gas data. Mixed effects linear modelling using generalised least‐squares estimation was used to assess treatment and speed main effects interaction. Significant differences (P<.01) were found between placebo and albuterol‐treated horses for total run time (mean ± s.e. 405.8 ± 8.8 vs. 430.5 ± 6.7 s) and run time from completion of 8 m/s until fatigue (169.3 ± 8.6 vs. 187.3 ± 6.7 s), as well as V̇O2peak (121.7 ± 3.7 vs. 130.3 ± 3.8 ml/kg/min), respectively. In conclusion, inhaled albuterol sulphate has a small but significant effect on the performance of fit Thoroughbred horses during incremental, V̇O2peak exercise testing.
Hyperbolic relationship between time‐to‐fatigue and workload
Authors: LAUDERDALE M. A. , HINCHCLIFF K. W.
Published: June 2010

The power:time‐to‐fatigue relationship for high‐intensity exercise in man is useful in determining anaerobic work capacity. The purpose of this study was to determine the nature of this relationship in horses. Eight Standardbred horses performed 5 or 6 run‐to‐fatigue trials on a treadmill. Exercise intensities were chosen to induce fatigue in 30 to 240 s. The order of trials was randomised for each horse, but balanced overall for the first 4 trials. The data for power (independent variable) and time‐to‐fatigue (dependent variable) were tested for goodness of fit to hyperbolic, linear and exponential equations by nonlinear regression. The best fit to the data was obtained using the hyperbolic relationship t = W'/(P‐ ØPA) where t is the time to fatigue, W' is the anaerobic work capacity, P is the power and ØPAis the critical power value. The values for W' and ØPAwere 47,000 ± 500 J and 2490 ± 150 watts, respectively. We conclude that the power:time‐to‐fatigue relationship of horses is hyperbolic and that this relationship may be useful in assessing anaerobic capacity of horses.
The effects of an endurance ride on metabolism and neutrophil function
Authors: JENSEN‐WAERN MARIANNE , LINDBERG åSA , JOHANNISSON A. , GRÖNDAHL GITTAN , LINDGREN J. å. , ESSÉN‐GUSTAVSSON BIRGITTA
Published: June 2010

The effects of an endurance ride on neutrophil functions in endurance‐trained horses were evaluated and related to metabolic changes and changes in cortisol concentrations. Blood samples were taken from 7 horses (aged 9–15 years) one day before, and then 30–60 min, 1 day and 8 days after the ride. The race resulted in elevated serum cortisol levels (<465 nmol/l) and an increased neutrophil:lymphocyte ratio. Immediately post race, the neutrophil ability to engulf yeast was increased. One day after the race, a decrease in leukotriene B4production (approximately 40%) and in the respiratory burst (approximately 75%) was observed.

Blood glucose concentration remained unchanged, as did serum lactate, which was low. After the race, the muscle glycogen stores were about 33% of the values noted after 8 days of recovery. Histochemical staining showed that 22 ± 2% of the muscle fibres were totally depleted of glycogen. CK activity increased significantly from 40 ± 10 mmol/min pre‐race to 228 ± 38 mmol/min post race. It was concluded that both hormonal and metabolic changes occurred during an endurance ride, which not only triggered neutrophil activation, but also induced alterations in their functional capacities.
Plasma glutamine status in the equine at rest, during exercise and following viral challenge
Authors: ROUTLEDGE NAOMI B. H. , HARRIS R. C. , HARRIS PAT A. , NAYLOR J. R. J. , ROBERTS C. A.
Published: June 2010

The variation over 24 h of plasma glutamine concentration in nonexercising horses was studied in 3 Thoroughbreds (TB) fed at 1600 h and 0700 h. This indicated a small but regular change associated with feeding. Starting at a mean of 482 μmol/l at 1600 h the concentration increased to 522 μmol/l at 2000 h, falling to 476 μmol/l at 1600 h and increasing again to 525 μmol/l at 2000 h. ‘Normal’ values were established in 19 part‐bred TB horses, lacking clinical signs or remarkable pathology and in light training, by sampling weekly at 1000 h over a 10 week period. The mean concentration was 491 μmol/l. Values were normally distributed with 95% confidence range between horses of 469–512 μmol/l. The s.d. of values within‐horse was 28 μmol/l. The acute effect of exercise was investigated in 5 TB horses during i) an exercise simulating the road and tracks phase of a 3‐day‐event and ii) a sustained high‐intensity exercise test (115% V̇O2maxuntil the pace was no longer maintained). In both tests a transient increase was produced as a direct result of exercise, followed by a decline to a nadir at approximately 3 h post exercise. Pre‐exercise resting concentrations, following either test, were approaching pre‐values by 24 h recovery. The effect of viral challenge was studied in 6 TB horses exposed to an aerosol of equine influenza virus, subtype H3N8 (A/equine‐2 subtype) which caused mild clinical signs. A significant fall in the 1000 h plasma glutamine concentration from a mean of 463 to 342 μmol/l by the 6th day was seen in 5 horses. A more gradual decline was observed in the 6th horse. These findings indicate a similar response to viral challenge in the horse to that in man.
Exercise‐ and metabolism‐associated blood variables in Standardbreds fed either a low‐ or a high‐fat diet
Authors: VAN OLDRUITENBORGH‐OOSTERBAAN M. M. SLOET , ANNEE M. P. , VERDEGAAL E. J. M. M. , LEMMENS A. G. , BEYNEN A. C.
Published: June 2010

Feeding a high‐fat diet increases fat utilisation and may decrease glycogen utilisation resulting in a lower lactate production during moderate exercise. The effects of fat feeding on exercise‐ and lipid metabolism‐associated blood variables were evaluated in 6 Standardbred horses during submaximal exercise. The horses were fed a high‐ (11.8% fat in total dietary dry matter) or a low‐fat diet (1.5% fat) in a cross‐over experiment with feeding periods of 4 weeks. At the end of each feeding period, the horses were subjected to a submaximal standardised stepwise exercise test on a treadmill. Blood samples were obtained prior to the start, during the last 10 s of each exercise step, and after recovery (40 min walking in hand). Pre‐exercise test values for plasma lactate, pH, pCO2, ionised sodium, ionised potassium, ionised calcium, ionised chloride, glucose, nonesterified fatty acids and glycerol did not differ for the 2 diets. The pre‐exercise concentration of triacylglycerols was significantly lower on the high‐ compared to the low‐fat diet (mean ± s.d. 0.17 ± 0.06 and 0.23 ± 0.08 mmol/l, respectively), whereas the concentrations of cholesterol (3.00 ± 0.47 and 2.11 ± 0.49 mmol/l, respectively), HDL cholesterol (1.80 ± 0.18 and 1.35 ± 0.27 mmol/l, respectively) and phospholipids (2.30 ± 0.11 and 1.72 ± 0.20 mmol/l, respectively) were significantly higher. There was significantly less plasma lactate accumulation during exercise when the horses were given the high‐fat diet (P = 0.011). Horses on a low‐fat diet had significantly different plasma lipid values when compared to being on a high‐fat diet. The alterations in these values during and after moderate exercise were comparable for both diets. These results indicate that fat metabolism is significantly adapted on a high‐fat diet; feeding such a diet may enhance potential performance by delaying lactate accumulation and thereby delaying the onset of fatigue.
Effects of fat adaptation on glucose kinetics and substrate oxidation during low‐intensity exercise
Authors: PAGAN J. D. , GEOR R. J. , HARRIS P. A. , HOEKSTRA K. , GARDNER S. , HUDSON C. , PRINCE A.
Published: June 2010

This study was designed to determine the effects of fat adaptation on carbohydrate and fat oxidation in conditioned horses during low‐intensity exercise. Five mature Arabians were studied. The study was conducted as a crossover design with 2 dietary periods, each of 10 week's duration: a) a control (CON) diet, and b) a fat‐supplemented (FAT) diet. The total amount of digestible energy (DE) supplied by the fat in the CON and FAT diets was 7% and 29%, respectively. During each period, the horses completed exercise tests at the beginning of the period (Week 0) and after 5 and 10 weeks on the diet. Tests consisted of 90 min of exercise at a speed calculated to elicit 35% V̇O2max on a treadmill inclined to 3°. Oxygen consumption (V̇O2), carbon dioxide production (VCO2), and respiratory exchange ratio (RER) were measured at 15‐min intervals. For determination of glucose kinetics, a stable isotope ([6‐6‐d2] glucose) technique was used. Compared to the CON diet, FAT diet consumption for 5–10 weeks was associated with an altered metabolic response to low‐intensity exercise, as evidenced by a more than 30% reduction in the production and utilisation of glucose; a decrease in RER; a decrease in the estimated rate of whole‐body carbohydrate utilisation; and an increase in the whole‐body rate of lipid oxidation during exercise.
Antioxidant supplementation and pulmonary function at rest and exercise
Authors: DEATON C. M. , MARLIN D. J. , ROBERTS C. A. , SMITH N. , HARRIS P. A. , KELLY F. J. , SCHROTER R. C.
Published: June 2010

Antioxidants have been implicated in the reduction and prevention of oxidative stress during exercise. We hypothesised that a dietary supplement containing a mixture of natural antioxidants together with vitamins E, C and selenium, given for 4 weeks, would increase the systemic and pulmonary antioxidant capacity leading to a reduction in markers of oxidative damage and an improvement in pulmonary function during exercise. In 6 healthy horses studied, the antioxidant supplement significantly increased plasma concentrations of ascorbic acid (from mean ± s.d. 16 ± 7 to 23 ± 4 μmol/l; P = 0.007) and α‐tocopherol (from 10 ± 3 to 14 ± 3 μmol/l; P = 0.02) and increased the bronchoalveolar lavage pulmonary epithelial lining fluid (ELF) concentration of ascorbic acid compared to a placebo, but not significantly (2.0 ± 0.9 mmol/l and 1.2 ± 0.9 mmol/l, respectively; P>0.05). α‐tocopherol was not detected in ELF either before or after supplementation or exercise. The mean concentration of malondialdehyde (MDA) in ELF was lower following antioxidant supplementation compared to placebo and control periods, but not significantly. An intermittent exercise test consisting of 2 min at 70, 80 and 90% of the horses' individual maximum oxygen uptake, failed to induce significant systemic or pulmonary oxidative stress (based on the glutathione redox ratio (GRR) and the ascorbic acid redox ratio (ARR)) and lipid peroxidation (based on the concentration of thiobarbituric acid reactive substances in plasma and MDA in ELF) either for placebo or antioxidant treatments. There was a strong correlation between GRR and ARR in the pulmonary epithelial lining fluid (r = 0.89; P<0.0001). In healthy horses on a diet containing adequate levels of antioxidants, additional antioxidant supplementation has no apparent beneficial or detrimental effect on pulmonary function during moderate intensity exercise. The importance of antioxidant supplementation may only become apparent if the diet is deficient in antioxidants, if exercise intensity is higher or more prolonged, or if disease or additional stresses are present.
Effect of dietary lipid on response to exercise: relationship to metabolic adaptation
Authors: DUNNETT C. E. , MARLIN D. J. , HARRIS R. C.
Published: June 2010

The aim of the present study was to relate changes in muscle oxidative capacity and free fatty acid flux in response to oil supplementation to fuel utilisation during subsequent exercise of varying intensities. Following 10 weeks of oil supplementation there was an increased capacity for fat utilisation during low and moderate intensity exercise as indicated by a lower respiratory exchange ratio (RER) (P<0.05). We suggest that this was contributed to by a parallel increase in the oxidative capacity of muscle as indicated by a significant increase in the activity of muscle citrate synthase (CS) (P<0.05) and trend towards an increase in z̀‐Hydroxy acyl CoA dehydrogenase (z̀‐HAD), (P>0.05). In addition, low and moderate intensity exercise was associated with an exercise‐induced increase in plasma free fatty acids (FFA) and there was an increased facility for uptake of FFA by working muscle from circulating triglycerides, as suggested by an increase in TL activity (P<0.01). The response to oil supplementation varied between individual horses and the magnitude of response, during the low intensity exercise test, in terms of difference in RER was correlated to the increase in CS activity (r2= 0.95, P<0.05) following oil supplementation. There was no similar significant correlation with respect to FFA, TL or z̀‐HAD activity (P>0.05). The hypothesis in this study was that the metabolic adaptation to oil supplementation, in terms of exercise response, was related to individual increases in the activities of CS, z̀‐HAD or TL. However, the relationship between these parameters was unequivocal and requires further investigation, ideally with a larger group of horses.
Comparison of the metabolic responses of trained Arabians and Thoroughbreds during high‐ and low‐intensity exercise
Authors: PRINCE A. , GEOR R. , HARRIS P. , HOEKSTRA K. , GARDNER S. , HUDSON C. , PAGAN J.
Published: June 2010

In order to compare the metabolic responses to exercise in 2 similarly managed breeds of horses, 5 Arabian (AR) and 5 Thoroughbred (TB) horses, fed an identical diet with a similar diet and exercise training programme for the 2 preceding months, undertook 3 treadmill (3° incline) trials with a minimum of 7 days between tests: 1) an incremental test (MAX) for determination of aerobic capacity, VLA4 and lactate threshold (LT; the percentage of V̇O2max when plasma lactate = 4 mmol/1); 2) a single high‐speed exercise test (SPR) at 115% V̇O2max for estimation of maximal accumulated oxygen deficit (MAOD) and 3) a 90 min test at 35% V̇O2max (LO).

V̇O2max (P<0.001) and running speed (P<0.05) at VO2max were higher in TB (mean ± s.e. 154 ± 3 ml/kg/min at 12.9 ± 0.5 m/s) than in AR (129 ± 2.5 ml/kg/min at 11.8 ± 0.2 m/s). Total run time during MAX was greater (P<0.05) in TB (10.5 ± 0.5 min) than in AR (9.3 ± 0.3 min). However, VLA4 and LT were not different between groups. Run time during SPR (TB 149 ± 16; AR 109 ± 11 s) and MAOD (TB 88 ± 4; AR 70 ± 6 ml O2/kg) were higher (P<0.05) in the TB group. During LO, FFA were higher (P<0.05) and the respiratory exchange ratio (RER) lower (P<0.05) in AR than in TB between 60 and 90 min, of exercise, indicating a greater use of fat for energy. These metabolic differences may reflect breed variation in muscle fibre types. However, further studies are needed to determine the mechanisms underlying the apparent breed differences in energy metabolism during exercise.
Use of the recovery check in long‐distance endurance rides
Authors: ROBERT C. , BENAMOU‐SMITH A. , LECLERC J.‐L.
Published: June 2010

In an attempt to reduce morbidity, an additional veterinary examination is performed at the end of the hold time ‐ the Recovery Check (RC) ‐ of the last vet gate of all long distance endurance rides held in France. At the RC, a normal FEI‐type inspection is performed combined with a cardiac recovery index (CRI): the heart rate is taken before (HR0) and 1 min after (HR1) the horse trotted for 30 m out and back. Results from 12 (130 and 160 km long) rides and based on 489 horses were analysed. Of all RC performed, 10.4% lead to elimination of the horses and lameness was the most frequent reason (45%). Among horses allowed to continue in the ride, elimination rate was significantly higher in horses with HR0>60/min compared to horses with HR0<60. High CRI (HR1‐HR0>4) lead to greater disqualification rates only when HR0was more than 60/min. RC appears to be useful in the assessment of a horse's fitness. However, standardisation of the examination is necessary in order to optimise its use.
A lactate‐guided conditioning programme to improve endurance performance
Authors: TRILK J. L. , LINDNER A. J. , GREENE H. M. , ALBERGHINA D. , WICKLER S. J.
Published: June 2010

Blood lactate measurements are used widely in horses to assess athletic performance, but there are few published data on using lactate as a guide for endurance improvement. The velocity at which blood lactate concentration ([LA]) of 4 mmol/I is reached (v4) is widely used to determine fitness. In an earlier study of v4, exercise at low intensities for longer duration was more effective at improving endurance than shorter, higher intensities. However, the prescription was unchanged during the study (6 weeks). We hypothesised that, to produce greater improvement in v4in the same time frame, it is necessary to adjust conditioning regimes more frequently. Six horses underwent an initial treadmill‐based standard exercise test (SET). A regression analysis [LA]‐speed relationship was used to calculate v2. Horses were then conditioned for 45 min at their calculated v23 times/week (6% incline). Every 2 weeks the horses performed an SET to evaluate the v2conditioning protocol which ended with SET 4. Mean v4increased 17% from SET 1 to SET 4 (P = 0.003; 5.8 ± 0.3 to 6.8 ± 0.4 m/s). This study demonstrates that a lactate‐guided conditioning programme can significantly enhance endurance performance over a 6‐week time peroid when the conditioning protocol is adjusted every 2 weeks based on v4improvement.
The cost of transport in an extended trot
Authors: WICKLER S. J. , HOYT D. F. , COGGER E.A. , McGUIRE R.
Published: June 2010

We hypothesised that trotters during an extended trot have lower energetic costs of locomotion (CT) than horses not bred for this behaviour. V̇O2 was measured as a function of speed in 7 Arabian horses (3 trained to extend their trotting speeds) and in 2 horses, of similar mass, bred to trot (Hackney). Both oxygen consumption and CT increased with speed and there was, contrary to our hypothesis, no difference between breeds. In Arabians at 6.5 m/s, CT had increased 25% above the CT at 5.0 m/s (normal transition speed). For Hackneys at 6.8 m/s, the CT was almost 35% higher. Stride frequencies increased linearly in all horses up to 5.0 m/s. At the canter at 5.0 m/s, the frequency increased 9% to 111 strides/min, but then increased minimally with speed. In the Hackneys and the Arabians that extended the trot, stride frequencies were approximately 102 and did not increase with speed. Stride length (SL) increased linearly with speed in both trotting and cantering horses, and cantering SL were lower than trotting (at 5.0 m/s, SL for trotting = 3.04 m and for cantering SL = 2.68 m). There were no differences between breeds in stride frequency or stride length.

Extending the trot can have profound energetic requirements that could limit athletic performance and may lead to increased concussive impact on the limbs.
Plasma lactate and uric acid responses to racing in pacing Standardbreds and relationships with performance
Authors: EVANS D. L. , PRIDDLE T. L. , DAVIE A. J.
Published: June 2010

Relationships between racing performance and plasma lactate and uric acid concentrations after racing were investigated in pacing Standardbred racehorses. The study was undertaken in order to better understand factors that limit racing performance. Twenty horses were tested after races of 1760 m and 28 horses after races over 2160 m. Blood samples were taken 30–60 min before and 8 and 30 min after a race. There were no significant differences between the race distances for prerace and 8 min postrace plasma lactates. Significant low correlations were obtained for plasma lactate concentration 8 min postrace and the number of race wins (r = 0.29, P = 0.04), number of race placings (1st, 2nd or 3rd; r = 0.34, P = 0.02) and lifetime earnings (r = 0.29, P = 0.04). Net lactate was correlated with the number of race placings (r = 0.31, P = 0.03). There were no significant correlations between performance indices and plasma uric acid concentrations in races of 1760 m. For races over 2160 m, correlations were found between plasma uric acid concentration at 8 min postrace and the number of race wins (r = 0.37, P = 0.06, 95% confidence limits 0‐0.65). As well, there was a significant correlation between uric acid concentration at 8 min postrace and lifetime earnings (r = 0.35, P = 0.07, 95% confidence limits 0.06‐0.64). Only 10–15% of the variability in retrospective career performance in pacing Standardbreds can be explained by these metabolic markers of the muscle anaerobic response to racing. Plasma lactate and uric acid responses to maximal exercise are unlikely to be useful for evaluating racing performance in pacing Standardbreds in univariate analysis.
Effect of frusemide on bodyweight loss and recovery in racing Standardbreds
Authors: COLEMAN R. J. , ST LAWRENCE A. C. , LAWRENCE L. M. , ROBERTS A. M.
Published: June 2010

This study was conducted to compare bodyweight (bwt) loss and recovery in Standardbred horses receiving frusemide compared to controls. Thirty Standardbred horses from 7 training stables that were racing at the Red Mile in Lexington, Kentucky, during the spring 2001 pari‐mutuel meeting were studied. Fourteen horses (FRU) received frusemide (250 mg/horse i.v.) 4 h prior to racing, while 16 horses (NFRU) did not received frusemide. Horses were weighed on the morning of race day, prior to warm‐up, after racing and the next day. Changes in bwt were calculated as percentage increase or decrease from initial bwt. Prior to warm‐up, FRU horses had a mean bwt reduction of 1.30 ± 0.63%, (P<0.01), compared to a 0.19 ± 0.63% increase for the NFRU horses. FRU horses had a greater (P<0.03) postrace bwt loss (3.55 ± 0.55%) than the NFRU horses (2.71 ± 0.66%). On the morning after racing, bwt was still below initial values by 0.90 ± 0.55 and 1.24 ± 0.35% for the FRU and the NFRU horses, respectively. While frusemide administration increased the postrace weight loss in racing Standardbreds, it did not affect short‐term bwt recovery. Further research is required into management strategies required to allow horses to replenish fluids and electrolytes safely following strenuous exercise.
Effects of weight carrying, exercise and a myo‐anabolic supplement on growth and muscle
Authors: O'CONNOR C. I. , NIELSEN B. D. , SCHOTT H. C. , CLAYTON H. M.
Published: June 2010

Weight training is commonly used by human athletes to increase strength and fitness. This study was performed to examine the effect of weight‐carrying and nutritional supplementation on muscle development and growth in yourn horses. This study examined the effect of weight‐carrying and nutritional supplementation on muscle development and growth. Seventeen horses were divided into 3 groups: controls exercised in a free‐flow exercise, a weight group that performed the same exercise, carrying progressively increasing weight up to 45 kg, and a weight‐supplement group, that also received a myo‐anabolic supplement. Horses were accustomed to handling for 30 days then baseline measurements of weight, body condition score, wither height, hip height, forearm and gaskin circumferences, and cross‐sectional area of the longissimus dorsi were taken. Horses were stalled for 108 days then conditioned for 78 days. At the end of conditioning, all measurements were taken again. Supplemented weight‐carrying horses increased their lean body tissue, as indicated by greater bodyweight (P<0.05) combined with decreased body condition score (P<0.01). Greater increases in wither height (P = 0.09) and hip height (P<0.01) were seen in weight‐carrying horses, probably the result of increased muscle tone. Supplemented weight‐carrying horses increased forearm (P<0.01) and gaskin circumferences (P<0.05). It is believed that weight‐carrying, when combined with additional dietary protein, enabled greater muscle anabolism. Additional research into the potential additive effect of resistance training and diet are warrented.
Changes in skeletal muscle GLUT4 content and muscle membrane glucose transport following 6 weeks of exercise training
Authors: McCUTCHEON L. J. , GEOR R. J. , HINCHCLIFF K. W.
Published: June 2010

This study examined changes in skeletal muscle GLUT4 content glucose transport in isolated muscle membranes (GT) from horses before and 2 min after standardised submaximal exercise tests (SET) prior to and after completion of 6 weeks of training. Seven horses, age 3–9 years, body mass mean ± s.e. 530 ± 19 kg, and sedentary for at least 4 months, completed 6 weeks of training on a treadmill. An initial SET (UT) was performed on a 4° incline at a speed equivalent to 55% of pretraining V̇02maxand was repeated post‐training at the same absolute workload (ABS). A third SET (REL) was performed at 55% of post‐training V̇02max.There was no significant pre‐ to postexercise change in GLUT4 content before or after training. Following training, total GLUT4 content was increased 2‐ or 3‐fold in pre‐exercise biopsies (pre UT: 0.30 ± 0.05; pre ABS: 1.05 ± 0.32; pre REL: 1.34 ± 0.28 arbitrary units) (P<0.05) with similar increases in postexercise GLUT4 content (P<0.05) (post UT: 0.33 ± 0.06; post ABS: 1.19 ± 0.44; post REL: 1.43 ± 0.31). GT increased 2.5‐ to 6‐fold in postexercise muscle membrane vesicles in UT over a range of glucose concentrations. After training (ABS and REL), there was a 25–50% attenuation (P<0.05) in membrane GT in response to exercise in ABS and REL. These finding indicate that moderate intensity exercise training increased middle gluteal muscle GLUT4 content, but this change was not reflected in an increase in muscle membrane glucose transport activity in postexercise muscle samples.
Pro‐ and macroglycogenolysis in skeletal muscle during maximal treadmill exercise
Authors: BRÖJER J. , JONASSON R. , SCHUBACK K. , ESSÉN‐GUSTAVSSON B.
Published: June 2010

The purpose was to investigate the degradation of proglycogen and macroglycogen in skeletal muscle during intense exercise. Ten Standardbred trotters performed a maximal treadmill exercise test comprising a warm‐up period, an exercise period, starting at 7 m/s with increments of 1 m/s every 60 s until the onset of fatigue (mean ± s.d. 246 ± 32 s) and a walking recovery period. Muscle biopsies were taken at rest, immediately after exercise and 15 min postexercise. The exercise caused a marked anaerobic metabolism as shown by the decrease in both muscle ATP and creatine phosphate and increase in muscle lactate. Free muscle glucose increased immediately postexercise and a further increase was noted 15 min later. There was a significant decrease (P<0.05) in proglycogen (57.1 ± 22.2 mmol/kg dw) and macroglycogen (63.0 ± 65.5 mmol/kg dw) during exercise. The proglycogen concentration tended to increase 15 min after exercise (19.9 ± 27.3 mmol/kg dw; P= 0.06). The results from this study demonstrate that both proglycogen and macroglycogen contribute equally to glycogenolysis during intense exercise and suggest that glycogen resynthesis starts in the proglycogen pool.
Inhibition of articular cartilage degradation by glucosamine‐HCl and chondroitin sulphate
Authors: ORTH M. W. , PETERS T. L. , HAWKINS J. N.
Published: June 2010

Glucosamine and chondroitin sulphate in many animal and human trials has improved joint health.In vitrostudies are beginning to clarify their mode of action. The objective of this research was to: 1) determine at what concentrations glucosamine‐HCl (GLN) and/or chondroitin sulphate (CS) would inhibit the cytokine‐induced catabolic response in equine articular cartilage explants and 2) to determine if a combination of the 2 was more effective at inhibiting the catabolic response than the individual compounds. Articular cartilage was obtained from carpal joints of horses (age 1–4 years). Cartilage discs (3.5 mm) were biopsied and cultured. Explants were incubated with lipopolysaccharide (LPS) in the presence of varying concentrations of GLN, CS, or both. Control treatments included explants with no LPS and LPS without GLN or CS. Media were analysed for nitric oxide (NO), prostaglandin E2(PGE2) and keratan sulphate. Cartilage was extracted for analysis of metalloproteinases (MMP). Four experiments were conducted. In all experiments, GLN at concentrations as low as 1 mg/ml decreased NO production relative to LPS stimulated cartilage without GLN over the 4 day period. In general, CS at either 0.25 or 0.5 mg/ml did not inhibit NO production. The addition of CS to GLN containing media did not further inhibit NO production. GLN at concentrations as low as 0.5 mg/ml decreased PGE2production, whereas CS did not effect on PGE2. The combination of GLN/CS decreased MMP‐9 gelatinolytic activity but had no effect on MMP‐2 activity. The combination in 2 experiments tended to decrease MMP‐13 protein concentrations and decreased keratan sulphate levels in media. Overall, the combination of GLN (1 mg/ml) and CS (0.25 mg/ml) inhibited the synthesis of several mediators of cartilage degradation. These results further support the effort to understand the role of GLN and CS in preserving articular cartilage in athletic horses.
Forelimb skeletal scintigraphy responses in previously untrained Thoroughbreds undergoing initial treadmill training
Authors: FOREMAN J. H. , KNELLER S. K. , TWARDOCK A. R. , CHAMBERS M. D. , INOUE O. J.
Published: June 2010

Scintigraphy has been used in numerous clinical settings to examine horses to determine the origin of lameness problems, but it has not been used previously to monitor prospectively the skeletal responses of a group of similarly‐trained racehorses. Our hypothesis was that in naive Thoroughbred (TB) racehorses, initial treadmill training induces increased radiopharmaceutical uptake in high‐motion joints and in the dorsal third metacarpal bone (MC3). Eight previously‐untrained TB racehorses underwent sequential skeletal scintigraphic examinations as they exercised daily for 9 weeks on an inclined treadmill. At the end of Weeks 0 (pre‐training), 3 (trotting at 4.2 m/s and initial galloping), 6 (galloping at 7.5 m/s), and 9 (sprinting 600 m at 12.5 m/s), horses received 140 mCi 99m Technetium‐methylene diphosphonate i.v. followed by a standard skeletal scintigraphic forelimb examination 2 h later. Views were graded for increased radiopharmaceutical uptake by 3 co‐investigators who were blinded to horse identification, breed, sex, date, and clinical findings. Results were compared before and after training for each skeletal location using the Mann‐Whitney Rank Sum Test with the level of significance set at P<0.05. Initial treadmill training resulted in increased radiopharmaceutical uptake in the carpus (P = 0.031), metacarpophalangeal joint (P = 0.021), proximal phalanx (P = 0.035), and distal phalanx (P = 0.003). Training did not affect dorsal MC3 radiopharmaceutical uptake (P>0.05).
Effect of training duration and exercise on blood‐borne substrates, plasma lactate and enzyme concentrations in Andalusian, Anglo‐Arabian and Arabian breeds
Authors: MUÑOZ A. , RIBER C. , SANTISTEBAN R. , LUCAS R. G. , CASTEJÓN F. M.
Published: June 2010

Metabolic responses to exercise differ between Andalusian horses and other breeds, although changes in plasma muscle enzymes have not been reported and most useful information is obtained from animals subjected to different training programmes. The objectives of this study were to 1) describe the changes in plasma enzymes during exercise in different horse breeds in relation to other biochemical parameters (Experiment A) and 2) assess the effect of training duration on these measures (Experiment B).

Twenty stallions, 9 Andalusian (AN), 7 Arabian (A) and 4 Anglo‐Arabian (AA), age 5–10 years, were studied. They performed 3 exercise tests (ET), consisting of a warm‐up of 800 m at 0.7 km/h and 4 workloads at 15, 20, 25 and 30 km/h, at respective distances of 1250, 1670, 2080 and 2500 m, with 5 min active recovery between each workload (Experiment A). Three ETs were performed at the beginning and after 2 and 6 months of training (Experiment B). Venous blood samples were collected during the ETs and plasma glucose (GLU), free fatty acids (FFA), lactate (LA), creatine kinase (CK), lactate dehydrogenase (LDH), α‐hydroxybutyrate dehydrogenase (HBHD), aspartate aminotransferase (AST), Na+, K+ and Cl− were measured.

AN horses responded to exercise with greater increases in GLU, HBHD, LDH, CK and AST compared to the other breeds. An unexpected result in Experiment A was the lack of interbreed differences in plasma peak LA concentrations, since it is commonly accepted that AA and A horses have greater athletic potential. Although the glycolytic response to exercise was reduced after 2 months of training in the AA and A horses, and after 6 months of training in the AN horses, at the end of Experiment B, AN horses produced more lactate than the other 2 breeds. Most of the adaptations linked to training were found in the AN breed. The more striking changes in plasma enzyme activities corresponded to CK in AN horses after 2 months of training. The attenuation of CK response to exercise was related to lower extrafibrilar GLU utilisation with LA formation and greater fat metabolism. The results show that plasma muscle enzyme concentrations for the diagnosis of equine myopathies must be interpreted in relation to breed and training.
Effects of prolonged training, overtraining and detraining on skeletal muscle metabolites and enzymes
Authors: McGOWAN C. M. , GOLLAND L. C. , EVANS D. L. , HODGSON D. R. , ROSE R. J.
Published: June 2010

Thirteen Standardbred horses trained intensively for 34 weeks and detrained for 12 weeks to investigate the effects of training, overtraining and detraining on muscle metabolites, buffering capacity and enzyme activities (CS, HAD and LDH). After a standardised exercise test to fatigue at 10 m/s (approximately 100% V̇O2max), there was significant depletion of [ATP], [PCr] and muscle [glycogen] and accumulation of muscle and plasma [lactate], [NH3] and elevated muscle temperature. After training, associated with increased run time to fatigue (148%), there was reduced depletion of muscle [glycogen] and increased [NH3] and muscle temperature at fatigue. Training resulted in increased muscle buffering capacity (19%) and activities of CS (29%) and HAD (32%) and reduced glycogen utilisation (1.32 mmol/s in week 1 to 0.58 mmol/s in week 32). Plasma [lactate] at fatigue increased with training as opposed to muscle [lactate] implying enhanced ability to remove lactate from muscle. Overtraining resulted in reduced run time and associated effects in overtrained horses. While muscle [glycogen] prior to exercise was lower in overtrained horses, glycogen utilisation/s was not reduced and it may not, therefore, have caused the reduced run time. Prolonged high intensity training caused primarily aerobic adaptations and poor performance associated with overtraining may not be due to metabolic disturbances.
Oral L‐carnitine combined with training promotes changes in skeletal muscle
Authors: RIVERO J. ‐L. L. , SPORLEDER H. ‐P. , QUIROZ‐ROTHE E. , VERVUERT I. , COENEN M. , HARMEYER J.
Published: June 2010

The purpose of this study was to determine whether oral L‐carnitine supplementation enhances the responses of skeletal muscle to training in seven 2‐year‐old Standardbreds. Four horses were supplemented with 10 g/day L‐carnitine for 10 weeks and 3 horses served as controls. All horses were exercised regularly every second day on a treadmill for 5 weeks (training period) and housed in individual boxes for 5 additional weeks (detraining period). The training period consisted of 8 high‐ and 8 low‐speed exercises carried out in alternating sequence. Gluteus medius muscle biopsies were taken at Weeks 0 (pretraining), 5 (post‐training) and 10 (detraining). Muscular adaptations to training were observed mainly in the L‐carnitine‐supplemented horses and included an increase in the percentage of type IIA fibres (δ35%, P<0.05), atrophy of type I fibres (δ24%, P<0.01), a rise in the capillary‐to‐fibre ratio (δ40%, P<0.01) and an increase in the quantitative reaction of periodic acid Schiff stain (δ11%, P<0.05), used as an indicator of intrafibre glycogen content. After detraining, most of these adaptations reverted towards the pretraining situation. Therefore, exogenous carnitine has an additive effect on muscular responses to training and this should be favourable to improve athletic performance. Nevertheless, further studies are necessary to show whether muscle carnitine content is a limiting factor for fatty acid oxidation.
Training‐induced apoptosis in skeletal muscle
Authors: BOFFI F. M. , CITTAR J. , BALSKUS G. , MURIEL M. , DESMARAS E.
Published: June 2010

Apoptosis or programmed cell death is a genetically controlled response of cells to commit suicide and is associated with DNA fragmentation or laddering. The common inducers of apoptosis include Ca2+i and oxygen free radicals/oxidative stress, which are also implicated in the pathogenesis of exercise‐induced myopathies. To examine training‐induced apoptosis, Thoroughbred horses were subjected to 3 months training programme on a treadmill. At the end of the training programme venous blood samples were taken for a creatine kinase (CK) assay. In addition, muscle biopsy samples were obtained for a membrane lipid peroxidation measurement by malondialdehyde (MDA) assay and for apoptosis detection. Apoptosis was studied by visualising the apoptotic myocytes on the paraffin sections by the modified TUNEL method. DNA laddering was evaluated by subjecting the DNA obtained from the biopsies to 1.5% agarose gel electrophoresis. There was a significant increase (P<0.05) of protein‐bound MDA, and a nonsignificant trend (P = 0.14) for the control group to have higher levels of CK compared to the trained group. Under light microscopy, percentage of the TUNEL positive cells was higher (P<0.001) in the training group. This result was corroborated with the findings of DNA fragmentation by gel electrophoresis, which showed higher ladders of DNA band at the same group. In conclusion, these results clearly demonstrate that there is training‐induced apoptosis in skeletal muscle. It is probable that apoptosis allows the work/recovery/rebound/supercompensation cycle, when unaccustomed muscle cells activate programmed cell death and are replaced by new and stronger cells, which is the mechanism for training‐induced increases in fitness.
Plasma carnosine concentration: diurnal variation and effects of age, exercise and muscle damage
Authors: DUNNETT M. , HARRIS R. C. , DUNNETT C. E. , HARRIS P. A.
Published: June 2010

This study was undertaken as part of a larger investigation into carnosine metabolism and function in the Thoroughbred horse. More specifically, we wished to evaluate plasma carnosine concentration as a potential indicator of muscle carnosine status. In contrast to man, carnosine is present in equine plasma where its presence is consistent with the absence of plasma carnosinase. A significant effect of age on plasma carnosine concentration in resting Thoroughbred horses was observed. Values in horses age 3 years and older were 11.3–14.1 μmol/***l, whereas concentrations in foals and yearlings were 3.9‐8.7 μmol/l (P<0.001). Lower values in young horses may reflect lower skeletal muscle carnosine concentrations. There was no significant within‐day variation in plasma carnosine concentration in fed and fasted horses (P>0.05). Intense exercise resulted in a small significant increase (P<0.05) in plasma carnosine concentration (pre‐exercise, 10.3 ± 1.0 μmol/l; postexercise, 12.4 ± 4.4 μmol/l). Greater increases were observed (57.6–702.3 μmol/l) following onset of exercise‐induced rhadomyolysis (ERS). An apparent relationship was observed between elevated plasma carnosine and increased plasma creatine kinase (CK) and aspartate transaminase (AST) activities. Plasma carnosine concentrations did not reflect the severity of the condition as determined by clinical examination. In conclusion, elevated plasma carnosine levels are observed following exercise induced muscle damage, with the greatest elevations occurring during episodes of external rhabdomylosis syndrome. Plasma carnosine measurements could provide an alternative clinical indicator of muscle damage; and in conjunction with plasma taurine measurements may be indicative of selective type 1 or type 2 muscle fibre damage. However, given the complexity of the analytical technique, its applications would probably be confined to specialist referral or research centres.
Effects of trotting speed on muscle activity and kinematics in saddlehorses
Authors: ROBERT C. , VALETTE J. ‐P. , POURCELOT P. , AUDIGIÉ F. , DENOIX J. ‐M.
Published: June 2010

A thorough knowledge of the horse's back and limb movements at different speeds is important in the design of training programmes and the prevention of speed‐related injuries. The objective of this study was to investigate changes in muscle activity and kinematics of the trot with increased speed. To evaluate these effects, 4 Saddlehorses were recorded while trotting on a horizontal treadmill at speeds ranging from 3.5–6.0 m/s. The 3‐D trajectories of skin markers on the left side of the horse and the dorsal midline of the trunk were established. Electrical activity was obtained simultaneously from 6 muscles using surface electrodes. Ten consecutive strides were analysed for each horse at each of the 5 velocity steps.

The increase in speed resulted in a decrease in stride and stance phase duration, increased muscle activity and range of motion of the limbs, but a decrease in back movements. During the stance phase, the limbs appeared more loaded, which resulted in more flexion of the joints and higher excentric muscle activity. During the swing phase, the higher concentric activity of the muscles was responsible for an increased shortening of the limbs.

Understanding the effects of speed on equine locomotion is a prerequisite for the development of training programmes.
Jumping characteristics of naïve foals: lead changes and description of temporal and linear parameters
Authors: SANTAMARÍA S. , BACK W. , van WEEREN P. R. , KNAAP J. , BARNEVELD A.
Published: June 2010

The selection of foals as future showjumpers remains a subjective process based on qualitative parameters; and hence, frequently suffers from disparity in the criteria used by experts in the field. A detailed biomechanical description of foals while jumping would be most helpful in providing a better basis for the accurate assessment of their future athletic ability. The Qualisys Pro Reflex system was used to capture 3‐dimensional kinematics of 41 Dutch Warmblood foals age 6 months free jumping a vertical fence, preceded by a cross pole fence. The left lead was the most preferred lead for both the fore‐ and hindlimbs, from the landing following the cross poles to the first move‐off stride after clearing the vertical fence. The foals displayed a high incidence of rotary gallop during both the jump stride (divided into take‐off, jump suspension and landing) and the first move‐off stride, while change of lead was frequently observed during jump suspension. At the take‐off side of the fence, the trailing forelimb in the last approach stride was placed furthest from the fence, whereas the trailing hindlimb at take‐off was placed closest (P<0.05). At the landing side, the trailing forelimb was the closest and the leading hindlimb of the move‐off stride 1 was the furthest (P<0.05). The trailing forelimb in the approach stride 1 had a significantly longer stance phase duration than the leading forelimb. At landing, the leading forelimb stance phase lasted longer than that of the trailing forelimb (P<0.05). The hindlimbs did not differ in their stance phase duration at take‐off. The height reached by the hooves above the fence top was significantly greater in the hind limbs (P<0.05). In addition, the hindlimbs (97.1 ± 2.6%) shortened more than the forelimbs (92.6 ± 5.7%) (P<0.05). It is concluded that the overall jumping technique of foals is similar to that reported in literature for mature horses. If the patterns are consistent throughout the rearing period, the quantitative analysis of the kinematics of free jumping foals may provide a valid quantitative basis for early selection.
Early evaluation of dressage ability in different breeds
Authors: BARREY E. , DESLIENS F. , POIREL D. , BIAU S. , LEMAIRE S. , RIVERO J.‐L. L. , LANGLOIS B.
Published: June 2010

Dressage is one of the Olympic equestrian sports practiced in several countries using different horse breeds. Specific characteristics of the walk, trot and canter are required for dressage. It has been assumed that some of these traits could be selected for genetically and contribute to dressage performance. The purpose of this study was to compare the walk, trot and conformation characteristics in young horses of different breeds used for dressage. A total of 142 horses age 3 years were classified into 3 groups of breeds (German, French and Spanish saddle horses) and tested using the same procedure. The skeletal conformation measurements were made by image analysis. Gait variables of the walk and trot were measured by the accelerometric gait analysis system Equimetrix. Discriminant analysis could explain the variability between the groups by taking into account the walk (P<0.0003), trot (P<0.0001) and conformation variables (P<0.0001). Many gait and conformation variables were significantly different between the breeds. In summary, the German horses had gait characteristics more adapted for dressage competition, and the results of this group could be used as a reference for early evaluation in dressage. Purebred Spanish horses could be considered as a reference for collected gaits used for farm work and old academic dressage. The gait and conformation tests could be applied in a breeding or crossing plan to detect more accurately young horses with good dressage ability.