bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of exercise on bone density in distal regions of the equine third metacarpal bone in 2‐year‐old Thoroughbreds
Authors: RIGGS C. M. , BOYDE A. 
Published: June 2010

SummaryThe present study addressed the question of whether training induces changes in bone density in the younger racehorse in regions relevant to the genesis of the common sagittal condylar fracture pattern and, if so, the nature of such alteration. Third metacarpal bones (McIII) were obtained from 12 experimental Thoroughbred, unbroken fillies, age 18.1–21.0 months at entry to the study. Six(Group E)undertook 19 weeks of progressive high intensity exercise on a high‐speed treadmill at 3% incline. Six(Group C)walked 40 min each day. Clinical bone density was studied by Computed Tomography (CT) of the right Mein. 1:1 aspects of bone density were studied by digital radiography of slices and microscopic aspects by backscattered electron (BSE) imaging.There was a distinct pattern of regional variation in bone density throughout the distal condyles of McIII. Bone density was greater in specimens fromGroup Ethan those fromGroup Cby CT, by radiographic density and by bone volume fraction as determined from backscattered electron images: the latter also showed that the most important change was in the increased amount of bone deposited within antecedent marrow space in cancellous tissue inGroup Ecompared withGroup C, with more extensive regional involvement in the highly loaded (distopalmar) aspects of the medial and lateral condyles. However, this space‐filling bone fraction had a lower degree of mineralisation than the prior bone tissue, showing that CT and radiography underestimate the resultant increased bone volume fraction. Stress fractures of the distal condyles of the McIII are common in Thoroughbred racehorses. We propose that excess stiffening within the condyles due to extensive new bone formation may lead to concentration of strain at the condylar grooves and incipient cracking through calcified cartilage and into the subchondral bone.
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

SummaryEight 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

SummaryThis 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

SummaryThe 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

SummaryThe 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

SummaryThe 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

SummaryFeeding 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

SummaryThis 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

SummaryAntioxidants 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

SummaryThe 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 &#x007a;̀‐Hydroxy acyl CoA dehydrogenase (&#x007a;̀‐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 &#x007a;̀‐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, &#x007a;̀‐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

SummaryIn 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

SummaryIn 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

SummaryBlood 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

SummaryWe 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.