bluuebunny/crossref_metadata_2025 huggingface dataset:
The physiological responses to simulated race tests on a track and on a treadmill in Standardbred trotters
Authors: NOSTELL K. , FUNKQUIST P. , NYMAN G. , ESSÉN‐GUSTAVSSON B. , CONNYSSON M. , MUHONEN S. , JANSSON A.
Published: June 2010

Reason for performing study:It is unclear to what extent the physiological response to a standardised treadmill exercise test simulating racing conditions resembles the circulatory and metabolic response observed after a simulated race on a track.

Objectives:To compare the physiological responses of a standardised treadmill exercise test used to simulate racing conditions and a simulated race performed on a track on the same Standardbred trotting horses, all in racing condition.

Methods:Six Standardbred trotters in racing condition performed a standardised inclined treadmill exercise test protocol simulating racing conditions (ST) and a simulated race on a field track (FT). Heart and respiratory rates, haemoglobin, packed cell volume (PCV), glucose, pH, total carbon dioxide and potassium in venous blood and plasma lactate and total plasma protein were measured before and immediately after exercise and during recovery.

Results:No differences were observed in heart rate, haemoglobin, PCV, total plasma protein, glucose concentrations after exercise and during recovery between the tests. Plasma lactate was higher and total carbon dioxide concentrations and pH were lower in blood at the end of exercise in the FT compared to the ST. Plasma lactate concentrations were still higher 30 min post exercise in the FT compared to the ST. Blood pH returned to resting values at 15 min of recovery for the ST and at 60 min of recovery for the FT. At 60 min of recovery total carbon dioxide concentrations had still not returned to resting values in any of the tests. Respiratory rate at the end of exercise and body temperature at 15 min of recovery was higher after the ST than the FT. Exercise caused an increase in blood potassium concentrations at the end of exercise in both tests, but concentrations were lower after the FT compared to the ST.

Conclusions:The haemodynamic response to the ST test at the end of exercise and during recovery, assessed from heart rate, Hb, and PCV, was similar to the response observed in the FT test. The differences observed in plasma lactate, blood pH and TCO2concentrations between the ST and FT show that anaerobic metabolism was greater in the FT as this test included a finish at maximal speeds.

Potential relevance:The treadmill test used in this study to simulate a race resembles the haemodynamic response but not the anaerobic metabolic response observed after a simulated race on a track.
A comparison of cross‐country recovery rates at CCI 2* with and without steeplechase competitions
Authors: MURRAY J. K. , SENIOR J. M. , SINGER E. R.
Published: June 2010

Reasons for performing study:Short format 3‐day events were introduced in 2004. Anecdotal reports suggested that horses were more tired on completion of the cross‐country phase of short format events when compared with horses completing the cross‐country phase of long format competitions, despite the absence ofPhases A, BandC.

Objectives:To compare the physiological parameters and haematological parameters of horses that had completed the cross‐country phase of a short format (SF) and a long format (LF) CCI 2* competition.

Methods:During a CCI 2* competition 69 competitors took part in the short format and 74 in the long format competition. Long format competitors completedPhases A, B, CandDand short format competitors completedPhase Donly.Phase D(the cross‐country course) was identical for both competitions. Two‐way ANOVA for repeated measures andpost hoctests were used to compare temperature, pulse and respiration rates of horses competing in both types of competition.Ttests were used to compare mean lactate and electrolyte concentrations, while U‐Mann Whitney tests were used to compare CK and AST levels measured in horses competing in the short and long formats of the event.

Results:Training schedules, age and previous competition experience were not significantly different between horses competing in the SF and LF competitions. On completion ofPhase D, SF horses had significantly higher PCV and significantly lower ionised calcium concentrations when compared with LF horses. LF horses had significantly higher heart rates than SF horses 10 min prior to startingPhase Dand immediately after completingPhase D; however, no other significant differences were found between the 2 groups of horses.

Conclusions:Only weak evidence was found to support the hypothesis that the workload for the horse in a SF CCI 2* competition is significantly different when compared to the LF CCI 2* competition.

Potential relevance:There is no beneficial or detrimental effect on horses that complete short format CCI 2* competitions as compared to those that complete long format CCI 2* competitions but further research is required into the physiological response of horses at CCI 3* and CCI 4* short format competitions.
Retrospective study of predictive variables for maximal heart rate (HRmax) in horses undergoing strenuous treadmill exercise
Authors: VINCENT T. L. , NEWTON J. R. , DEATON C. M. , FRANKLIN S. H. , BIDDICK T. , McKEEVER K. H. , McDONOUGH P. , YOUNG L. E. , HODGSON D. R. , MARLIN D. J.
Published: June 2010

Reasons for performing study:Heart rate is one of the most commonly measured variables in equine exercise physiology and relative exercise intensity commonly expressed as % of maximal heart rate. A number of influences affect maximal heart rate (HRmax), including age of the horse but other factors have not been described.

Objectives:To determine if fitness, health status, gender, breed, athletic use, body mass, in addition to age, are predictive of HRmaxin the horse.

Methods:Maximal heart rate data from 328 horses which underwent treadmill exercise tests at 5 different laboratories were obtained retrospectively. Univariable linear regression analyses were performed on individual variables. Multiple linear regression analysis using a backward elimination modelling procedure was then used to relate the observed HRmaxvalues simultaneously with different predictive variables. Variables were retained in the final regression model if they or any of their categories were significantly predictive of HRmaxat P<0.05 and if there was a significant collective contribution to the model from inclusion of each variable, also at P<0.05.

Results:Age, fitness status, laboratory, gender and breed/use (combined category) were all statistically significantly predictive of HRmax. Together these variables accounted for 41% of the variance in HRmax. Age alone accounted for only ˜13% of the variation between horses in HRmax. Neither body mass nor health status were significantly predictive.

Conclusions:HRmaxin the horse declines with age but is also influenced by other factors. As the factors investigated accounted for only 41% of the variation between horses, other unidentified variables with a strong influence on HRmaxremain to be identified.

Potential relevance:Factors such as fitness, age, gender, breed and use need to be considered when interpreting estimates or measurements of HRmax.
Cardiac arrhythmias during and after treadmill exercise in poorly performing Thoroughbred racehorses
Authors: JOSE‐CUNILLERAS E. , YOUNG L. E. , NEWTON J. R. , MARLIN D. J.
Published: June 2010

Reasons for performing study:The prevalence and severity of cardiac arrhythmias during exercise in athletic horses presented for poor performance is not well described.

Objectives:To describe prevalence and severity of ventricular and supraventricular arrhythmias immediately before, during and immediately after standardised incremental treadmill exercise tests (IET) to fatigue in Thoroughbred horses during investigation of poor performance.

Methods:The electrocardiograms (ECG) of 88 Thoroughbred racehorses, judged to be free of significant heart disease or arrhythmia at rest, were used. A modified base‐apex ECG was recorded throughout an IET to fatigue. Recordings were analysed independently by 2 observers. Twenty‐eight horses were diagnosed with dorsal displacement of the soft palate, 25 had varying degrees of soft palate instability and aryepiglottic fold collapse, 8 had other respiratory problems and, in 27 cases, no definitive diagnosis was reached.

Results:Fifty‐five horses had at least one ventricular (VPD) or supraventricular (SVPD) depolarisation, 23 had only VPDs, 17 had only SVPDs and 15 had both in at least one exercise period. Premature depolarisations were seen predominantly during the first min of recovery from IET. The range of premature beats after exercise was 1–30 VPDs, and 1–9 SVPDs. No significant associations were observed between age, sex, race type, diagnosis, peak heart rate or run time to fatigue during IET and occurrence of either 1 premature beat or of more severe arrhythmias (multiple singles [>5] or pairs or paroxysms of premature depolarisations during peak exercise or immediately after exercise). However, a larger sample size would be required to have greater confidence in these associations.

Conclusions:Isolated VPDs and SVPDs are frequently detected in poor performing racehorses during IET but their clinical relevance remains to be determined.

Potential relevance:The guidelines for interpretation and clinical relevance of premature depolarisations observed during and immediately after treadmill exercise tests in poor performing Thoroughbred racehorses deserves further evaluation.
Effect of detraining on cardiorespiratory variables in young Thoroughbred horses
Authors: MUKAI K. , OHMURA H. , HIRAGA A. , ETO D. , TAKAHASHI T. , ASAI Y. , JONES J. H.
Published: June 2010

Reasons for performing study:Thoroughbred racehorses often experience interruptions to their training. Identifying the effects of these changes and how they alter athletic performance might provide an insight on to how to prevent these changes from occurring.

Hypothesis:Training and detraining young Thoroughbreds alters their aerobic capacities with correlated changes in circulatory capacities; if horses remained spontaneously active in a pasture during their detraining period, their decreases in aerobic capacity during detraining would be reduced.

Methods:We trained 6 Thoroughbred yearlings for 6 months using a conventional yearling race training programme. They were then detrained for 10 weeks with free range on pasture for 8 h/day and stall rest at night. Treadmill measurements of O2transport variables were made before training (PRE), after training (TR) and after detraining (DT). A step‐test protocol identified each horse's aerobic capacity (VO2max) and speed to attain it, and a steady‐state run at VO2maxwas used to quantify O2transport variables at each time period.

Results:The mass‐specific and whole‐body VO2max, cardiac output (Q) and stroke volume (Vs) increased from PRE to TR. All mass‐specific values decreased significantly from TR to DT; however, because body mass increased by 8.3% from TR to DT, none of the variables changed significantly from TR to DT on a whole‐body basis.

Conclusions:Changes in aerobic capacity are highly correlated with changes in Vs and circulatory capacity during training and detraining. Exercise activity of trained young horses free at pasture for 8 h/day is sufficient to maintain VO2max, Q and Vsduring 10 weeks of DT.

Potential relevance:Aerobic and cardiovascular fitness may be maintained in young Thoroughbred horses during at least 10 weeks of detraining by maintaining modest spontaneous exercise activity.
Heart rate variability in trotters during different training periods
Authors: KINNUNEN S. , LAUKKANEN R. , HALDI J. , HANNINEN O. , ATALAY M.
Published: June 2010

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.
Low dose exogenous erythropoietin elicits an ergogenic effect in Standardbred horses
Authors: McKEEVER K. H. , AGANS J. M. , GEISER S. , LORIMER P. J. , MAYLIN G. A.
Published: June 2010

Reasons for performing study:Recombinant human erythropoietin (rhuEPO) causes an increase in red blood cell production and aerobic capacity in other species; however, data are lacking on effects in the horse.

Hypothesis:This study tested the hypothesis that rhuEPO administration would alter red cell volume (RCV), aerobic capacity (VO2max) and indices of anaerobic power.

Methods:Eight healthy, unfit mares accustomed to the laboratory and experimental protocols were randomly assigned to either a control (CON, n=4; 3 ml saline 3 times/week for 3 weeks) or EPO group (EPO, n = 4, 50 iu/kg bwt rhuEPO/3 ml saline 3 times/week for 3 weeks). Exercise tests (GXT) were performed on a treadmill (6% incline), 1 week before and 1 week after treatment. The GXT started at 4 m/sec, with a 1 m/sec increase every 60 sec until the horse reached fatigue. Oxygen uptake was measured via an open flow indirect calorimeter. Blood samples were collected before, during (each step) and 2 and 15 min post GXT to measure packed cell volume (PCV), haemoglobin concentration (Hb), blood lactate concentration (LA) and plasma protein concentration (TP). Plasma volume (PV) was measured using Evans Blue dye. Blood volume (BV) and RCV were calculated using PCV from the 8 m/sec step of the GXT.

Results:There were no alterations (P>0.05) in any parameters in CON horses. By week 3, EPO produced increases (P<0.05) in resting PCV (37 ± 2 vs. 51 ± 2) and Hb (37%). RCV (26%) and VO2max(19%) increased, but BV did not change (P>0.05) due to decreased PV (‐11%, P<0.05). There was a significant increase in velocity at VO2maxand LApeakfor horses treated with rhuEPO and substantial decrease (P<0.05) in VO2recovery time when the pretreatment GXT was compared to the post treatment GXT. No differences (P<0.05) were detected for TP, VLA4, run time or Vmax.

Conclusions:Low dose rhuEPO administration increases RCV and aerobic capacity without altering anaerobic power.

Potential relevance:This study demonstrates that rhuEPO enhances aerobic capacity and exercise performance, a question relevant to racing authorities.
Influence of training on plasma adrenaline and noradrenaline kinetics in untrained Standardbreds
Authors: BARAGLI P. , DUCCI M. , GATTA D. , GAZZANO A. , SIGHIERI C.
Published: June 2010

Reasons for performing study:Catecholamines (CAT) play an important role in modulating the response to exercise. But the kinetics of CAT changes during exercise are difficult to study due to their short biological half‐life.

Objectives:Learning about variations in plasma CAT levels during training could furnish new information regarding sweating, redistribution of blood flow and energy metabolism.

Methods:Four untrained Standardbreds, adapted to treadmill work, were used to determine the influence of training on plasma adrenaline (A) and noradrenaline (NA) kinetics. Horses underwent a standardised exercise test (SET) on treadmill before (SET1), and 1 (SET2) and 2 months after (SET3) the start of a moderate training period on treadmill. The SET procedure was: warm‐up and a single step of 2 min at 200 beats/min heart rate (SS). The automatic blood collection system (that has been carried out during SS) and the preparation of the horses have been described previously. The system was programmed to obtain a blood sample every 15 sec (8 blood samples per SS). Analyses were performed by HPLC. Training progress was monitored by means of anaerobic threshold velocity (V4) and the velocity during SS (V200). Wilcoxon's test was used for statistical analysis.

Results:Decreased levels of A and NA with significant differences between SET1/SET2 and SET1/SET3 for A (P=0.007) and NA (P=0.007) were found. There were no differences between SET2 and SET3 for A (P=0.195) and NA (P = 0.054).

Conclusions:Training appears to influence the level of plasma CAT and this influence is greater during the first training period in untrained Standardbreds.

Potential relevance:It may prove interesting to associate the study of training‐induced modifications of the concentration of plasma CAT with thermoregulation, which is under catecholaminergic control and undergoes important adaptations during training.
The effect of adrenergic suppression induced by guanabenz administration on exercising Thoroughbred horses
Authors: COLAHAN P. T. , SAVAGE K. A. , TEBBETT I. R. , RICE B. L. , JACKSON C. A. , FRESHWATER L.
Published: June 2010

Reasons for performing study:Adrenergic activity accompanies intense exercise and mediates physiological and metabolic responses to exercise. Guanabenz, an antihypertensive drug marketed for human usage, depresses brain vasomotor and cardioaccelerator centres, blocks peripherally adrenergic neurons and is reportedly used as a calming agent in horses but little is known of its effects in the species.

Objectives:To determine if guanabenz induces measurable signs of adrenergic suppression on fit Thoroughbred horses undergoing intense exercise.

Methods:In a random crossover design, 12 exercise conditioned Thoroughbred horses each received guanabenz (0.08 mg/kg bwt i.v.) and placebo at 3‐week intervals. An incremental exercise test to exhaustion on a treadmill followed treatment by 1 h. Heart rate, oxygen consumption, carbon dioxide production, plasma lactate, catecholamines, adrenocorticotropic hormone (ACTH) and cortisol, and time to fatigue were monitored. Statistical analysis was performed using mixed‐effects linear modelling.

Results:Mean heart rate during the exercise period was lower in guanabenz‐treated horses (P=0.04). Mean concentrations of plasma cortisol (P=0.02) and adrenaline (P=0.03) were lower for guanabenz‐treated horses during the exercise period. Mean run time was slightly but not significantly longer for guanabenz‐treated horses, (P = 0.053). No significant effects of guanabenz administration were found for oxygen consumption, carbon dioxide production nor for plasma lactate, noradrenaline and ACTH concentrations.

Conclusion:Guanabenz administration induced signs of adrenergic suppression including plasma cortisol and adrenaline concentrations and heart rate and may enhance endurance, but did not eliminate increases in hormone concentrations induced by exercise. Clear determination of a positive performance effect of adrenaline, but not noradrenaline, suppression is needed before clinical significance can be determined.
Plasma β‐endorphin, cortisol and immune responses to acute exercise are altered by age and exercise training in horses
Authors: MALINOWSKI K. , SHOCK E. J. , ROCHELLE P. , KEARNS C. F. , GUIRNALDA P. D. , McKEEVER K. H.
Published: June 2010

Reasons for performing study:Ageing appears to affect immune and neuroendocirne function in horses and response to acute exercise. No studies have examined the combined effects of training and ageing on immune and neuroendocirne function in horses.

Hypothesis:To ascertain whether training and age would affect the plasma β‐endorphin (BE) and cortisol (C) as well as immune function responses to acute exercise in Standardbred mares.

Methods:Graded exercise tests (GXT) and simulated race tests (SRT) were performed before and after 12 weeks training at 60% HRmax. BE and C were measured at rest and at 5, 10, 20, 40, 60 and 120 min post GXT. Leucocyte cell number, CD4+and CD8+lymphocyte subsets, and mitogen stimulated lymphoproliferative response (LPR), were measured in jugular blood before and after the SRTs.

Results:Cortisol rose by 5 min post GXT in young (Y) and middle‐age (MA) mares (P<0.05) and remained elevated until 40 and 60 min post GXT, respectively during both pre‐ and post training GXT. There was no rise in C in old (O) mares after either GXT (P>0.05). Pretraining BE rose (P<0.05) by 5 min post GXT in all mares. After training, BE was higher in Y and O vs. MA (P<0.05) at 5 min post GXT. Post training BE was higher at 5 min post GXT in Y and O vs. pretraining (P<0.05). After SRT, lymphocyte number rose in all mares (P<0.05); however, lower lymphocyte numbers (P<0.05) were seen in MA vs. Y and O vs. MA (P<0.05). The O had reduced LPR to Con A and PHA stimulation (P<0.05) compared to Y and MA after the SRT after both pre‐ and post training SRT. LPR to PWM was lower (P<0.05) in O vs. Y and MA after the pretraining SRT. Training caused an increase in resting LPR to PWM in MA only (P<0.05).

Conclusion:Both age and training altered the plasma β‐endorphin and cortisol responses as well as and immune responses to acute exercise.

Potential relevance:This study provides important information on the effects of ageing and training that will aid in the management and care of an increasing number of active older horses.
The effects of dietary N‐3 and antioxidant supplementation on erythrocyte membrane fatty acid composition and fluidity in exercising horses
Authors: PORTIER K. , de MOFFARTS B. , FELLMAN N. , KIRSCHVINK N. , MOTTA C. , LETELLIER C. , RUELLAND A. , Van ERCK E. , LEKEUX P. , COUDERT J.
Published: June 2010

Reasons for performing study:Fatty acid supplementation could modulate erythrocyte membrane fluidity in horses at rest and during exercise, but information is lacking on the effect of exercise.

Objectives:To assess the effect of exercise with, and without, an oral antioxidant supplementation enriched with n‐3 fatty acids on erythrocyte membrane fluidity (EMF) and fatty acid composition in eventing horses.

Methods:Twelve healthy and regularly trained horses were divided randomly into 2 groups:group Sreceived an oral antioxidant cocktail enriched in n‐3 fatty acid (alphatocopherol, eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) whereasgroup Pwas placebo‐treated. At the end of 4 weeks, all horses performed a standardised exercise test (ET) under field conditions. Venous blood was sampled before starting treatment (T0), immediately before (T1) as well as 15 min (T2) and 24 h (T3) after ET. Spin labelled (16‐DOXYL‐stearic acid) red blood cell membranes were characterised using the relaxation correlation time (Tc in inverse proportion to EMF). Fatty acid composition (%) of the membrane was determined by gas‐liquid chromatography.

Results:Supplementation did not induce changes in EMF (T1 vs. T0) but significant changes in membrane composition were observed and there were increases in n‐3 polyunsaturated fatty acid PUFA, n‐3/n‐6 ratio, and total n‐3 fatty acids. Exercise (T2 vs. T1) induced a significant decrease of EMF ingroup P(Tc: +19%, P<0.05) and nonsignificant decrease ingroup S(Tc: +5%), whereas membrane fatty acid composition did not change in either group. During the recovery period (T3 vs. T2), EMF decreased significantly ingroup S(Tc: +29%, P<0.05) and nonsignificantly ingroup P(Tc: +18%) without any significant changes in fatty acid composition.

Conclusion and potential relevance:An enriched oral antioxidant supplementation induced changes in membrane composition, which modulated the decrease in EMF induced by exercise. Long chain n‐3 fatty acid supplementation might therefore be beneficial.
Hydration of exercised Standardbred racehorses assessed noninvasively using multi‐frequency bioelectrical impedance analysis
Authors: WALLER A. , LINDINGER M. I.
Published: June 2010

Reasons for performing study:In human and animal clinical practice, multi‐frequency bioelectrical impedance analysis (MF‐BIA) is increasingly used as a diagnostic tool to assess hydration of intra‐and extracellular fluid compartments. Accurate determination of changes in hydration status within individuals over time has remained problematic due to the requirement for complete impedance‐frequency relationships at the time points of interest.

Objectives:To use MF‐BIA in 13 Standardbred racehorses and 7 ‘endurance’ research horses to determine if MF‐BIA could be used to track changes in total body water (TBW), intracellular fluid volume (ICFV) and extracellular fluid volume (ECFV) resulting from exercise.

Methods:Jugular venous blood was sampled at rest and for 2–13 h following exercise. TBW, ECFV and plasma volume (PV) were measured at rest using indicator dilution techniques (D2O, thiocyanate and Evans Blue, respectively). TBW, ECFV, ICFV and PV were correlated to impedance measures and predictive equations used to determine hydration status from MF‐BIA measures.

Results:TBW loss continued throughout the recovery period, and was primarily borne by the ECF compartment at 90 min of recovery.

Conclusions:MF‐BIA predictions of compartmental hydration status were significantly correlated to measured/calculated decreases in these compartments.

Potential relevance:Practical applications for MF‐BIA in horses include monitoring of hydration status during transport and competition, assessment of body compostion, clinical health assessment and critical care management.
Is improved high speed performance following frusemide administration due to diuresis‐induced weight loss or reduced severity of exercise‐induced pulmonary haemorrhage?
Authors: ZAWADZKAS X. A. , SIDES R. H. , BAYLY W. M.
Published: June 2010

Reasons for performing study:Prerace administration of frusemide to horses has been linked with a significant improvement in racing performance, but the basis for this improvement is unclear.

Objective:To test whether improved performance with prerace administration of frusemide is due to the drug's diuresis‐induced weight loss rather than its apparent alleviation of exercise‐induced pulmonary haemorrhage (EIPH).

Methods:Eight thoroughbred horses underwent 3 trials in a random order, 2 or 3 weeks apart: control (C), frusemide/unburdened (FU), and frusemide/burdened (FB). None of the horses were known to have exhibited post‐exercise epistaxis or endoscopic evidence of EIPH. Endoscope‐guided bronchoalveolar lavages (BALs) were performed before and after each horse completed a standardised exercise test (SET) on an inclined treadmill to assess semi‐quantitatively the volume of EIPH. For C, horses received an i.v. saline placebo injection (5 ml) and were unburdened while performing the SET. With FU, horses received frusemide (0.5 mg/kg) and were also unburdened. For FB, horses received frusemide and were burdened with weight equal to that lost during the 4 h post frusemide injection period. Erythrocyte number in BAL fluid, mass specific VO2max, time and distance for the entire SET as well as at maximum speed were recorded. A one‐way repeated measures analysis of variance was conducted on all results.

Results:Mass specific VO2maxwas significantly higher for the FU than for FB or C. Mass specific VO2maxfor FB and C were not different. More RBCs were found in BAL samples after C runs than after both FU and FB trial runs. Horses with the frusemide treatment (either burdened or unburdened) produced less EIPH than in the C trial, but their mass specific VO2maxvalues were higher on the FU trial alone. For FU, horses ran longer at 115% VO2maxthan under C or FB conditions.

Conclusion and potential relevance:Improvement of performance in the furosemide trials was due more to the weight‐loss related effects of the drug than its apparent alleviation of EIPH. Further research is warranted with the same or similar project design, but with a larger sample size and with horses known to have more severe EIPH.
Effects of a pre‐moistened multilayered breathable fabric in promoting heat loss during recovery after exercise under hot conditions
Authors: FOREMAN J. H. , BENSON G. J. , FOREMAN M. H.
Published: June 2010

Reasons for performing study: Horses generate considerable internal heat burdens when exercising. Although common practice for a trainer or groom to place a wet blanket or towel on the dorsum of a hot horse post exercise, there are no data supporting the efficacy of this cooling method.

Objective: To test the hypothesis that a pre‐moistened blanket designed with a multilayered breathable fabric would enhance heat loss in horses post exercise.

Methods: Eight treadmill‐trained horses performed a standardised exercise test (SET) weekly for 3 weeks, with 3 different recovery treatments administered randomly. Pulmonary artery temperature (PAT) was measured via Swan‐Ganz catheter. The SET consisted of 10 min at 3.7 m/sec, 3 min at 11.0 m/sec, 25 min at 3.7 m/sec and 20 min of recovery walking at 2.0 m/sec (58 min exercise and recovery under laboratory conditions of 35.0–40.6°C and 27–49% RH). From 3–7 min during recovery, the treadmill was stopped and horses randomly received either: (a) no bath (negative control); (b) a bath consisting of 32 1 of 1–4°C water split into 3–4 cycles of bilateral water application (positive control) followed by water removal (‘scraping’); or (c) application of a multilayered fabric blanket soaked in 16–19°C water, wrung out, and placed over the dorsum and sides of the horse. PAT was compared using RM ANOVA with the Student Neuman‐Keul's test usedpost hocto discriminate between treatments at specific points in time.

Results: Mean PAT rose with each phase of exercise (P<0.001) and peaked at a mean of 40.2 ± 0.2°C. During recovery, the cold bath decreased HR and PAT for 9 min after walking resumed (P<0.001‐P<0.05). The blanket did not decrease HR or PAT compared to negative control (P>0.05), and both were hotter than the cold bath treatment through 16 min of recovery (P<0.05).

Conclusions: A specially‐designed cooling blanket failed to reduce PAT when compared to negative control. Cold water bathing decreased HR and PAT but was not effective throughout all of recovery.

Potential relevance: A specially‐designed, pre‐moistened multilayered breathable fabric failed to promote evaporative cooling compared to negative control. Cold water baths may need to be repeated throughout recovery to optimise their effect.
Contribution of exercise intensity and duration to training‐linked myosin transitions in Thoroughbreds
Authors: RIVERO J. L. , RUZ A. , MARTI‐KORFF S. , LINDNER A.
Published: June 2010

Reasons for performing study: The influence of relevant exercise parameters such as intensity and duration of exercise on the muscular response to training has not been reported in Thoroughbreds. This knowledge may be of great value in practice.

Objective: To define the relative contribution of the intensity and duration of exercise on the myosin heavy chain (MHC) response to training in Thoroughbred racehorses.

Methods: Six 2–3‐year‐old Thoroughbreds, following a randomised 6 times 6 latin square design, performed 6 consecutive conditioning programmes of varying lactate‐guided intensities and durations. Each programme lasted 22 days and consisted of 11 exercise sessions once a day, every second day on a 6% inclined treadmill followed by a 10 day resting period between consecutive programmes. Gluteus muscle biopsies (depth, 2 and 6 cm) were taken before, and after, each programme and electrophoretically analysed for MHCs.

Results: Overall, training increased the fraction of MHC HA (mean ± s.d., 41.1 ± 3.5% to 43.4 ± 4.42% P<0.001) and decreased that of MHC IIX isoform (from 50.2 ± 4.4% to 47.4 ± 5.6% P<0.001). Exercise intensity fixed effects on fast MHCs were highly significant (P<0.01), whereas exercise duration only had a marginal effect (P<0.1) on the IIA:IIX MHC ratio. On a per‐individual basis, training impact on fast MHCs was only significant (P<0.05) in horses exercised for the longest duration at both intensities.

Conclusion: The short‐term training‐induced up‐regulation of MHC IIA and down‐regulation of MHC IIX in Thoroughbreds are more dependent on intensity than duration of exercise. However, protocols with exercises of moderate intensity and long duration can induce MHC changes similar to those promoted by programmes with exercises of higher intensities.

Potential relevance: Exercises for up to 25 min/day at velocities eliciting a blood lactate concentration between 2.5 and 4 mmol/1 every second day for 3 weeks improve stamina in Thoroughbreds.
MCT1 and CD147 gene polymorphisms in Standardbred horses
Authors: REEBEN M. , KOHO N. M. , RAEKALLIO M. , HYYPPÄ S. , PÖSÖ A. R.
Published: June 2010

Reasons for performing study:Transport of lactate across membranes is facilitated by proton‐monocarboxylate transporters (MCT). The most widely distributed isoform is MCT1, which needs an ancillary protein CD147. Studies on erythrocytes have shown that high activity of MCT1 is inherited as the dominant allele and that activity is regulated through CD147. Mutations of human MCT1 have been described that appear to impair lactate transport in muscles and cause exertional rhabdomyolysis. There are no reports of this potential relationship in the horse.

Objectives:To obtain sequences of equine MCT1 and CD147 to examine differences between horses with high and low lactate transport activity in their erythrocytes.

Methods:Muscle biopsy samples were taken from 3 healthy Standardbred horses and from 7 horses which according to the owners had signs of myopathy after intense exercise. DNA and RNA were isolated and PCR analysis and sequencing performed.

Results:Currently, PCR fragments covering 100% of MCT1 and 70% of CD147 coding region are retained and sequence analysis has demonstrated one single nucleotide polymorphism (SNP) in the C‐terminal area of MCT1 and one SNP in the extracellular domain of CD147. Both cause an amino acid change. The SNPs found are not related to lactate transport activity in erythrocytes or signs of myopathy.

Conclusions:More samples need to be analysed to make conclusions on the significance of the polymorphisms found. Furthermore, full sequence coverage of the coding region of CD147 is needed.

Potential relevance:The molecular probes produced could be used as tools to study gene regulation of lactate transport.
Effects of prior exercise on components of insulin signalling in equine skeletal muscle
Authors: McCUTCHEON L. J. , GEOR R. J. , PRATT S. E. , MARTINEAU E. , HO K.
Published: June 2010

Reasons for performing study:Exercise is an important stimulus for the regulation of numerous metabolic functions in muscle, but there has been little investigation of the mechanism of exercise‐enhanced glucose utilisation.

Objective:To examine the effects of exercise on the signalling components Akt and glycogen synthase kinase‐3 (GSK3) involved in insulin regulation of glycogen synthase (GS) activity. It was hypothesised that hyperinsulinaemia and prior exercise would alter the extent of Akt phosphorylation and GSK3β deactivation and increase insulin stimulation of GS activity in skeletal muscle.

Methods:Eight Standardbred horses completed a euglycaemic‐hyperinsulinaemic clamp (EHC) either without prior exercise (NonEX) or at 0.5, 4 or 24 h post exercise (0.5 PostEX, 4 PostEX, and 24 PostEX, respectively). Muscle samples for determination of Akt and GSK3 serine phosphorylation, and GS fractional velocity (GSFV) were collected 5 min before (Pre‐INS) and at the end (Post‐INS) of each EHC (pre‐ and post insulin stimulation). Protein was separated by SDS‐PAGE on polyacrylamide gels, transferred to nitrocellulose membranes and incubated with antibodies against phospho‐Akt Ser473and GSK3α/β Ser21/9.

Results:GSFVwas increased (P<0.05) 2‐fold at 0.5 PostEX, 4 PostEX and 24 PostEX when compared to NonEX in Pre‐INS and in Post‐INS was increased 33 and 28% in NonEX and at 24PostEX (P<0.05), respectively, when compared to Pre‐INS in these trials. Phospho‐Akt Ser473was increased at 0.5 PostEX only (P<0.05) in Pre‐INS but increased in all trials in Post‐INS. Phospho‐GSK3α (Ser21) was also greater (P<0.05) at 0.5 PostEX in Pre‐INS than in NonEX and 24 PostEX and in Post‐INS increased (P<0.05) in NonEX and at 24 PostEX but not at 0.5 PostEX or 4 PostEX post exercise. There was no effect of time or treatment on GSK3, (Ser9) phosphorylation or on total GSK3.

Conclusions:Elevated plasma insulin and prior exercise were associated with Akt activation and GSK3α deactivation (0.5 PostEX) indicating that an effect of exercise is evident in the early post exercise period and supporting a physiological role for GSK3α in the regulation of GS activity. The changes are consistent with insulin signalling downstream from these molecules.
Monocarboxylate transporters (MCT) as lactate carriers in equine muscle and red blood cells
Authors: KOHO N. M. , HYYPPÄ S. , PÖSÖ A. R.
Published: June 2010

Reasons for performing study: Monocarboxylate transporters (MCT) facilitate the transport of lactate across membranes. In red blood cells (RBC) the transport activity varies interindividually due to differences in the amount of an ancillary protein CD147. Similar variations in muscles could have a great influence on lactate accumulation during exercise.

Objectives: To study the expression of MCT isoforms and CD147 in the middle gluteal muscle.

Methods: Venous blood and muscle biopsy samples were taken from 14 Standardbred horses. Lactate transport activity in RBC and the amounts of MCT1, 2, 4 and CD147 were measured.

Results: In muscle MCT1, MCT4 and CD147 were found. Amount of MCT1 was variable and not dependent on age or training. Expression of MCT4 increased with age and correlated positively with CD147. CD147 in muscle correlated with that in RBC. MCT4 in muscle and CD147/MCT1 in RBC were higher in race fit than in moderately trained horses.

Conclusions: MCT isoform profile in equine muscle is similar to that in man. The correlation between CD147 in muscle and RBC supports the view that lactate transport activity in muscles may vary interindividually as with RBC.

Potential relevance: A larger number of horses need to be analysed to confirm the relationship of CD147 in muscle and RBC; and to allow the use the lactate transport activity in RBC as an indicator of the respective activity in muscles.
Gene expression profiling in equine muscle tissues using mouse cDNA microarrays
Authors: MUCHER E. , JAYR L. , ROSSIGNOL F. , AMIOT F. , GIDROL X. , BARREY E.
Published: June 2010

Reasons for performing study:Progress could be achieved by using microarrays to understand metabolic adaptations and disorders in equine muscle in response to exercise.

Objectives:To test the feasibility of using mouse cDNA microarrays to analyse gene expression profile in normal equine muscles.

Methods:Muscular biopsies of dorsalgluteus mediusandlongissimus lumborumwere done in 4 healthy Standardbreds. Total RNA was extracted from the muscle samples. The concentration and quality of RNA were measured before and after amplification. Gene expression profiles were measured using mouse cDNA microarrays including 15,264 unique genes representing about 11,000 documented genes. Three hybridisation tests were performed to check interspecificity, reproducibility and to compare gene expression in these muscles. For each test, a dye‐swap hybridisation with Cy3 and Cy5 fluoromarkers were done and the gene list filtered according the signal level.

Results:According to the specificity test, the mouse cDNA microarrays were correctly hybridised by equine muscle cDNA. All positive control genes (GAPDH, HPRT and beta‐Actin) and no negative control gene (yeast, plant) hybridised. The reproducibility test demonstrated a good linearity between the duplicate hybridisations: 99.99% of the significant expressed genes have an expression ratio between 1.4 and 1/1.4 = 0.71. These limits can be considered as the thresholds to qualify as up‐regulated (ratio >1.4) or down‐regulated (ratio <0.71). In the muscle comparison test betweengluteus mediusvs.longissimus lumborum, 63 genes were found up‐regulated and 8 genes down‐regulated. The range of gene expression ratios in thegluteus mediuswas 0.61‐8.31 x thelongissimus lumborum.This list of modulated genes was classified by functions using a gene ontology data basis.

Conclusion:Mouse microarrays could be used to hybridise equine RNA extracted from muscle tissues. For many genes there are large sequence identities that allowed interspecific cDNA hybridisation. The sensitivity of the method allowed quantification of up‐ and down‐regulated genes after applying appropriate filters.

Potential relevance:Expression profiling could be used to explore the muscle metabolism changes related to exercise, training, pathology and illegal medication in horses.
Effects of egg‐bar shoes on the 3‐dimensional kinematics of the distal forelimb in horses walking on a sand track
Authors: CHATEAU H. , DEGUEURCE C. , DENOIX J. ‐M.
Published: June 2010

Reasons for performing study:Understanding of the biomechanical effects of egg‐bar shoes remains incomplete because kinematic studies are usually performed on hard tracks and with skin markers that do not measure the actual 3‐dimensional (3D) movements of the 3 digital joints.

Objective:To quantify the effects of egg‐bar shoes on the 3D kinematics of the distal forelimb in horses walking on a sand track.

Methods:Four healthy horses were equipped with ultrasonic markers fixed surgically to the 4 distal segments of the left forelimb. The 3D movements of these segments were recorded while the horses were walking on a sand track. Rotations of the digital joints were calculated by use of a joint coordinate system. Data obtained with egg‐bar shoes were compared to those obtained with standard shoes. Mean differences were expressed in a 0.95 confidence interval.

Results:With egg‐bar shoes, the initial sinking of the heels into the ground during landing was reduced and the heels were raised by up to 5.1° (3.5–6.7°) compared to standard shoes at mid‐stance. Concurrently, maximal flexion of the distal (DIPJ) and proximal (PIPJ) interphalangeal joints was increased by up to 3.2° (2.2–4.2°) and 1.8° (1.1–2.5°), respectively, at the beginning of the stance phase. At heel‐off, extension of the DIPJ was reduced by 3.8° (2.6–5.0°). In extrasagittal planes of movement, egg‐bar shoes prevented sinking of the medial quarter into the ground which led to a slight decrease of DIPJ medial rotation and lateromotion.

Conclusions:Egg‐bar shoes prevent the heels and, to a lesser extent, the medial side of the hoof from sinking into the ground on a sand track. They contribute to a decrease of DIPJ maximal extension at heel‐off and to hoof stabilisation in the transversal plane.

Potential relevance:Such quantitative results support the clinical indications of egg‐bar shoes.
Estimating peak strains associated with fast exercise in Thoroughbred racehorses
Authors: DAVIES H. M. S.
Published: June 2010

Reasons for performing study:The third metacarpal bones (MC3) of racing Thoroughbreds are a common site for bone damage. The midshaft dorsal cortex (DC) of MC3 thickens in response to fast exercise. It is not clear if it changes to a shape and size that limits the peak bone strains to a range associated with normal loading in other species.

Objectives:To relate the proportionate size of the DC cortex in racehorses exercising at racing speed to surface strains, and test whether the DC reached a plateau that was sustained through subsequent exposures to racing speed exercise.

Methods:Standardised lateral MC3 radiographs were taken weekly for 2–5 years in 40 racehorses in race training (16–19 m/sec). DC, medulla (M), and palmar cortex (PC) thickness were measured, at 2.5 cm distal to the nutrient foramen. An index (RI) of the relative thickness of the DC was calculated for each radiograph (RI = [DC+PC]/ M multiplied by [DC/PC]) and used to calculate strains at 12 m/sec from an equation published previously.

Results:Mean time to plateau in DC thickness was 501 days, mean increase in DC was 3.9 mm on the left and 3.7 mm on the right. Rate of change was 8.8 μm/day on the left, and 8.4 μm/day on the right during this time. In most horses the medulla width did not change between the first and last measurements so these bone growth rates reflect periosteal bone growth on the DC surface. No further significant change in DC or RI was found, once they had reached a plateau. Mean DC thickness at the plateau was 14.7 mm on the left and 14.9 mm on the right. Mean RI at the plateau was 3.7. This equated to peak microstrains at 12 m/sec of ‐2492 and suggests that strains much greater than 3000 microstrains occur at racing speed in most horses.

Conclusions:Experienced racehorses are likely to be exposed to peak strains beyond the normal limit for adult mammalian bone to resist without damage and strains associated with very fast exercise may not be sufficient stimulus to induce further bone modelling in these horses.

Potential relevance:Strains occur in the bones of experienced racehorses at a higher level than normal for other mammalian bones. Hence there may be other mechanisms operating in this particular bone in racehorses that protects the bone from failure when exposed to the high strains associated with fast exercise speeds. Investigation of such mechanisms may provide an insight on how to reduce the likelihood of damage to this bone during very fast exercise.
Gait pattern of the ataxic horse compared to sedated and nonsedated horses
Authors: STROBACH A. , KOTSCHWAR A. , MAYHEW I. G. , PEHAM C. , LICKA T.
Published: June 2010

Reasons for performing study:Equine ataxia is routinely evaluated subjectively by clinicians; however, objective measurements of the movement and coordination of ataxic horses have not been reported.

Objectives:To document the movement pattern of ataxic horses and compare the results to the movement of neurologically sound horses with, and without, sedation.

Methods:Seventeen ataxic horses were evaluated walking and trotting on a treadmill using a 3D high speed video system. From the horizontal movement of hoof markers the autocorrelation function (ACF) of the left forelimb and the cross correlation function (CCF) between the left forelimb and other 3 limbs (CCF foreleft/hindright [flhr], foreleft/hindleft [flhl], foreleft/foreright [flfr]) was calculated. This resulted in a value of motion cycle consistency. The results were compared to data of 17 neurologically normal horses with, and without, sedation with detomidine. For statistical analysis thettest for independent samples was used.

Results:Comparing normal (NO) and ataxic (AT) horses at the walk, highly significant differences for the ACF and for all the CCFs were documented. At the trot, ACF and CCFs flhr and flfr were significantly different in the NO and AT groups. Comparing sedated and ataxic horses, only the CCF flfr at walk and at trot were significantly different.

Conclusion and potential relevance:Ataxia is best documented and examined at the walk. At trot pendulum effect may make coordination easier for horses. The results of this study serve as basic data for evaluating questionably ataxic horses.