Endurance in horses refers to the ability of these animals to sustain prolonged physical activity, often assessed in the context of endurance racing or long-distance riding. This capability is influenced by a combination of physiological, genetic, and environmental factors. Key aspects of equine endurance include cardiovascular efficiency, muscular stamina, and metabolic adaptations that allow for sustained energy production. Research in this area often focuses on the mechanisms of energy metabolism, the impact of training regimens, and the genetic markers associated with endurance performance. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, genetic, and environmental determinants of endurance in horses.
Serteyn D, Sandersen C, Lejeune JP, de la Rebière de Pouyade G, Ceusters J, Mouithys-Mickalad A, Niesten A, Fraipont A, van Erck E, Goachet AG....Intense physical exercise can induce the degranulation of neutrophils leading to an increase in plasma concentration of the neutrophil marker enzymes myeloperoxidase (MPO) and elastase (ELT). These enzymes have pro-oxidative and pro-inflammatory properties and may play a role in the exercised-induced muscular damage. Objective: To measure MPO and ELT concentrations in plasma and muscles of endurance horses and to correlate them to the extent of exercise-induced muscular damage. Methods: Seven endurance horses qualified on 120 km races were tested in this study. Neutrophil count, serum creatine...
Barnes A, Kingston J, Beetson S, Kuiper C.This study investigated the physiology of endurance horses competing in warm weather over technical terrain, a situation where horses may become metabolically compromised. Objective: There will be changes in physiological, haematological and biochemical variables as horses progress through the 160 km ride and horses detected clinically at the veterinary inspections as metabolically compromised will have significant differences in measured laboratory variables compared to horses that complete the ride successfully. Methods: Forty-eight horses competing in the Australian Tom Quilty 160 km endura...
Viu J, Jose-Cunilleras E, Armengou L, Cesarini C, Tarancón I, Rios J, Monreal L.Acid-base disturbances are traditionally assessed using the Henderson-Hasselbach equation. The simplified strong ion approach describes more accurately the complex acid-base and electrolyte abnormalities present in endurance horses. Objective: To describe acid-base and electrolytes changes in fit horses competing in a FEI*** 120 km endurance race and to compare the traditional vs. strong ion approaches. Methods: Thirty horses were initially enrolled in the study. Venous blood samples were obtained before the race (n = 25), at the second (n = 29; 65.4 km) and third vet-gates (n = 23, 97.4 km) a...
De Mello Costa MF, Anderson GA, Davies HM, El-Hage CM, Slocombe RF.Investigate angiotensin converting enzyme (ACE) activity in equine plasma as a predictor of performance in endurance competitions and the effect of endurance exercise on ACE activity. Objective: Precompetition values of ACE activity in equine blood are correlated with performance results and with heart rates pre- and post competition used as indicators of fitness. Endurance exercise increases ACE activity. Methods: Nineteen horses participating in an 80 km endurance competition had venous blood samples collected before and after the ride. ACE activity and total protein were measured in the blo...
Cywinska A, Gorecka R, Szarska E, Witkowski L, Dziekan P, Schollenberger A.Changes in serum levels of acute phase proteins (APPs) reflect the acute phase reaction, a rapid and nonspecific response to any tissue damage. Serum amyloid A (SAA) is the main APP in horses, which increases in various diseases, surgical injuries and after long distance endurance rides; however, this nonspecific parameter has not been investigated as an indicator of subclinical disorders, which may result in elimination during endurance competitions. Objective: To evaluate the serum concentration of SAA as a potential indicator for the status of horses prepared for long distance endurance rid...
Trigo P, Castejon F, Riber C, Muñoz A.Endurance races are the competition with the biggest metabolic demands for the sport horse. During races, some horses show homeostasis alterations, having repercussions in diverse biochemical parameters and negative consequences on performance and health. Objective: To evaluate the utility of biochemical analysis in the early diagnosis of metabolic stress and to determine cut-off values of biochemical parameters to assist in the prevention of metabolic alterations in endurance horses. Methods: This study involved 36 CEI races and 283 horses (41 eliminated because of metabolic disturbances). Bl...
Sloet van Oldruitenborgh-Oosterbaan MM, Genzel W, van Weeren PR.Welfare concerns over the reasons for interruption or termination of a sporting career in horses have been expressed. Objective: To study the career of competition horses and factors that influence career length. Methods: In 2004, 46,576 rider-horse combinations were registered with the Dutch National Equestrian Federation (KNHS) in dressage, show jumping, eventing and endurance. From this population, approximately 1% of horses in each discipline were selected at random and all recorded competition data from the KNHS registration system collected and supplemented by detailed rider/owner teleph...
Treiber KH, Boston RC, Geor RJ, Hess TM, Harris PA, Kronfeld DS.Tools and criteria to evaluate and understand glucose metabolism are essential to optimise equine energy utilisation for exercise performance and reduced metabolic health risks. Objective: To re-evaluate models of glucose kinetics in the horse at rest and during endurance type exercise using a single injection technique and compartmental modelling. Methods: Twelve exercise trained Arabian geldings received a bolus of 100 µmol/kg bwt [6,6-(2) H]glucose i.v. while at rest and while running at ∼ 4 m/s on a treadmill. Tracer and tracee glucose curves from 4-150 min after the bolus dose (while t...
Holbrook TC, McFarlane D, Schott HC.The inflammatory and neuroendocrine response to endurance exercise and relationship of these parameters to performance is not well documented in horses. HYPOTHESES OR OBJECTIVES: Evidence of systemic inflammation is associated with poor performance in horses competing in endurance events. Methods: Blood was collected prior to and at the finish or elimination point from horses competing in both the 80 and 160 km American Endurance Ride National Championship competitions in 2006. Immunoreactive alpha-melanocyte stimulating hormone (α-MSH) and tumour necrosis factor-alpha (TNF-α) were quantifie...
Tamzali Y, Marguet C, Priymenko N, Lyazrhi F.Equine gastric ulcers syndrome (EGUS) prevalence studies are rare in the endurance horse and none has been carried out to date in horses competing at high level. Objective: To determine the prevalence of EGUS in high-level endurance horses. Methods: Thirty endurance horses competing at high level were selected and submitted to 2 gastroscopic examinations. The first gastroscopy was performed during the interseason period, and the second during the competition season within 2-3 days following a ride of 90-160 km. Data related to housing, feeding, training system as well as age, breed and gender ...
Yamano S, Kawai M, Minami Y, Hiraga A, Miyata H.We evaluated differences in muscle fiber recruitment patterns between continuous and interval training to develop an optimal training program for Thoroughbred horses. Five well trained female thoroughbred horses (3-4 years old) were used. The horses performed two different exercises on a 10% inclined treadmill: 90%VO2 max for 4 min (continuous) and 90% VO2 max for 2 min × 2 times with 10-min interval (interval). Muscle samples were obtained from the middle gluteal muscle before and immediately after the exercises. Four muscle fiber types (type I, IIA, IIA/X, and IIX) were immunohistochemicall...
Campbell EH.Equine conditioning programmes are rarely driven by science. Indeed, the scientific literature on conditioning responses often refers to conventional technique rather than physiological driving parameters. This, alongside poor classification of conditioning protocols, has reduced the possibility of comparative data analysis. Recent interest into lactate-driven conditioning programmes has driven this review which provides a summary of equine protocols used to date and their responses. Key areas identified for further standardisation and/or investigation include (1) the treadmill acclimation pro...
Capomaccio S, Cappelli K, Barrey E, Felicetti M, Silvestrelli M, Verini-Supplizi A.It is known that moderate physical activity may have beneficial effects on health, whereas strenuous effort induces a state resembling inflammation. The molecular mechanisms underlying the cellular response to exercise remain unclear, although it is clear that the immune system plays a key role. It has been hypothesized that the physio-pathological condition that develops in athletes subjected to heavy training is caused by derangement of cellular immune regulation. The purpose of the present study was to obtain information on endurance horse gene transcription under strenuous conditions and t...
Muñoz A, Riber C, Trigo P, Castejón F.Arginine vasopressin (AVP) is released in response to depletion of the effective circulating blood volume. Endurance horses might develop exhaustion because loss of water and electrolytes in sweat with hypovolaemia and electrolytes abnormalities. Therefore, AVP should act in the control of volemia in these animals. This research evaluates the differences in AVP, hydration, electrolyte status and serum muscle enzymes in successful endurance horses in comparison with those eliminated from the competition because of exhaustion. Eighteen endurance horses, divided into two groups, successful (n = 1...
Cywińska A, Wyszyńska Z, Górecka R, Szarska E, Witkowski L, Dziekan P, Winnicka A, Schollenberger A.Strenuous exercise is recognized as a stress, which may induce functional immunodeficiency and increase individual susceptibility to infection. It has been shown in equine athletes, that alterations in leukocyte functions occur after moderate and submaximal exertion, however, no data deal with the effect of extreme physical exertion. In this study, we evaluated leukocyte functions (neutrophil oxidative burst and lymphocyte proliferation activity in response to mitogens) in horses following the CEI 3* 162 km endurance ride. Exercise-induced stress was manifested as neutrophilic leukocytosis and...
Lindner AE.The speed producing the maximal lactate steady state (maxLASS) is supposed to be the optimal speed to condition for endurance. The maxLASS was defined as the maximal speed at which the blood lactate concentration ([LA]) between the 5th and the 25th min of continuous exercise did not increase by more than 1 mmol/L. According to the aerobic-anaerobic lactate threshold concept determined in humans, maxLASS corresponds to v(4) [speed in a standardized exercise test (SET) shown to produce an [LA] of 4 mmol/L; generalized to v(i) for the speed producing an [LA] of i mmol/L]. Four Thoroughbreds were ...
Fielding CL, Magdesian KG, Rhodes DM, Meier CA, Higgins JC.To describe the clinical and clinicopathologic abnormalities in endurance horses eliminated from competition and requiring emergency medical treatment. Methods: Retrospective study over a 2-year period (2005-2006). Ten horses that successfully completed the ride in 2006 were included for comparison. Methods: Temporary equine emergency field hospital. Methods: All horses (n=30) that were removed from endurance competition and treated for a metabolic abnormality were studied. Methods: Horses were treated with IV fluids and analgesics. Monitoring included lab work (PCV, total protein, and electro...
Haggett E, Magdesian KG, Maas J, Puschner B, Higgins J, Fiack C.Exercise causes an increase in the production of reactive oxygen species, which can result in oxidant/antioxidant disequilibrium. Deficiency of antioxidants can further alter this balance in favor of pro-oxidation. Selenium (Se) is one of many antioxidant catalysts, as a component of the glutathione peroxidase enzymes. Soils and forages vary widely in Se concentration and a deficient diet can lead to sub-clinical or clinical deficiency in horses. Endurance horses are prone to oxidative stress during long periods of aerobic exercise and their performance could be affected by Se status. This stu...
Harris P.This article reviews the principles of feeding management for endurance horses. The amount and type of dietary energy (calories) are key considerations in dietary management, because (1) there is evidence that the body condition score, an indicator of overall energy balance, influences endurance exercise performance, and (2) the source of dietary energy (ie, carbohydrate versus fat calories) impacts health, metabolism, and athletic performance. Optimal performance is also dependent on provision of adequate feed, water, and electrolytes on race day.
Cappelli K, Felicetti M, Capomaccio S, Spinsanti G, Silvestrelli M, Supplizi AV.Adequate stress response is a critical factor during athlete horses' training and is central to our capacity to obtain better performances while safeguarding animal welfare. In order to investigate the molecular mechanisms underlying this process, several studies have been conducted that take advantage of microarray and quantitative real-time PCR (qRT-PCR) technologies to analyse the expression of candidate genes involved in the cellular stress response. Appropriate application of qRT-PCR, however, requires the use of reference genes whose level of expression is not affected by the test, by ge...
Treiber KH, Geor RJ, Boston RC, Hess TM, Harris PA, Kronfeld DS.Advances in modeling and tracer techniques provide new perspective into glucose utilization and potential consequences to health or exercise performance. This study used stable isotope and compartmental modeling to evaluate how adaptation to a feed high in sugar and starch (SS) compared with a feed high in fat and fiber (FF) affects glucose kinetics at rest and during exercise in horses. Six trained Arabians adapted to each feed underwent similar tests at rest and while running approximately 4 m/s on a treadmill. For both tests, horses received 100 micromol/kg body weight [6,6-(2)H]glucose thr...
Muñoz A, Cuesta I, Riber C, Gata J, Trigo P, Castejón FM.Trot is a symmetric gait and asymmetry might appear or increase during endurance rides due to lameness, pain or excessive fatigue. Objective: To assess whether trot asymmetry increases during endurance competitions, whether it is possible to discriminate between horses with different performance and also its possible relationship with metabolism. Methods: Fifty-eight horses were filmed at trot during the lameness examinations in the vet-gates, before the competition (BCO), and after phases 1 (at 29 km), 2 (at 59 km) and 3 (at the end of the ride, at 80 km) and stride duration (SD) measured in ...
Riber C, Cuesta I, Muñoz A, Gata J, Trigo P, Castejón FM.Fatigue during endurance rides might induce changes in gait pattern that could be difficult to distinguish from subtle lameness. Objective: To assess changes in gait pattern en route, in fore(FL) and hindlimbs (HL) and establish differences between excellent (EP) and good performers (GP). Methods: Seventy-five sound and fit horses that completed endurance rides of 80 km were filmed at trot in the vet-gates (VGs) prior to competitions (VGO), and at 29 km (VG1), 59 km (VG2) and 80 km (VG3). Mean gait velocity (V), stride length (SL), duration (SD) and frequency (SF) were measured. Also, stance (...
Kinnunen S, Laukkanen R, Haldi J, Hanninen O, Atalay M.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. Objective: 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 an...
Wickler SJ, Greene HM, Egan K, Astudillo A, Dutto DJ, Hoyt DF.The relationship between fatigue and stride and/or muscle stiffness requires further study. Objective: To measure stride parameters in horses undergoing fatigue associated with running at submaximal speeds both on a treadmill and in an endurance ride. Objective: Stride frequencies and estimates of hindlimb stiffness would be decreased in fatigued horses. Methods: Horses were fatigued using 2 paradigms: run to exhaustion at a treadmill (4.5 m/sec, 6% incline) and finishing an 80 km endurance ride. Videos were digitised before and after fatigue and analysed for stride parameters: hind limb lengt...
Colahan PT, Savage KA, Tebbett IR, Rice BL, Jackson CA, Freshwater L.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. Objective: 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...
Art T, Franck T, Gangl M, Votion D, Kohnen S, Deby-Dupont G, Serteyn D.In man, exercise of any type has been shown to induce neutrophil degranulation and respiratory burst activity, as well as an increase in plasma myeloperoxidase (MPO), a specific enzyme of neutrophil azurophilic granules with a strong oxidative activity. Until now, it is not known whether this is the same in horses. Objective: To study whether degranulation of blood neutrophils may be induced by exercise by measuring the total concentration of MPO and assess the possible influence of type of competition on this exercise-induced adjustment. Methods: Blood was sampled before, and 30 min after, th...
Holbrook TC, Birks EK, Sleeper MM, Durando M.Information is lacking regarding the influence of long distance exercise on the systemic concentration of cardiac troponin I (cTnI) in horses. Objective: To determine if the concentration of cTnI in horses competing in 80 and 160 km endurance races increases with exercise duration and if cTnI concentrations can be correlated with performance data. Methods: Blood samples for the measurement of cTnI and 3 min electrocardiogram recordings were obtained from horses prior to, during and after completion of 80 and 160 km endurance races at 3 ride sites during the 2004 and 2005 American Endurance Rid...
Sampieri F, Schott HC, Hinchcliff KW, Geor RJ, Jose-Cunilleras E.There is no evidence that use of oral electrolyte pastes enhances performance in competing endurance horses. Objective: To ascertain whether oral administration of a high dose (HD) of sodium chloride (NaCl) and potassium chloride (KCl) to endurance horses would differentially increase water intake, attenuate bodyweight (bwt) loss and improve performance when compared to a low dose (LD). Methods: A randomised, blinded, crossover study was conducted on 8 horses participating in two 80 km rides (same course, 28 days apart). Thirty minutes before and at 40 km of the first ride 4, horses received o...
Graves EA, Schott HC, Marteniuk JV, Refsal KR, Nachreiner RF.Limited information exists about changes in circulating thyroid hormone concentrations during prolonged endurance exercise in horses. Objective: To examine the effects of prolonged exercise on serum iodothyronine concentrations in horses performing endurance exercise of varying distances. Methods: Serum concentrations of iodothyronines were measured in horses before and after completion of 40, 56, 80 and 160 km endurance rides (Study 1); daily during a 5 day, 424 km endurance ride (Study 2); and before and for 72 h after completion of a treadmill exercise test simulating a 60 km endurance ride...
Flethøj M, Kanters JK, Pedersen PJ, Haugaard MM, Carstensen H, Olsen LH, Buhl R.Although premature beats are a matter of concern in horses, the interpretation of equine ECG recordings is complicated by a lack of standardized analysis criteria and a limited knowledge of the normal beat-to-beat variation of equine cardiac rhythm. The purpose of this study was to determine the appropriate threshold levels of maximum acceptable deviation of RR intervals in equine ECG analysis, and to evaluate a novel two-step timing algorithm by quantifying the frequency of arrhythmias in a cohort of healthy adult endurance horses. Results: Beat-to-beat variation differed considerably with he...
Rose RJ.Blood counts and noradrenaline estimations were performed in 14 horses competing in a 160 km endurance ride. Samples were collected before the ride, immediately after the ride. 30 minutes after the ride and the day after the ride. For statistical analysis, a group of seven horses that completed the ride at a mean speed of 234 m/minute (fast group) was compared with seven horses that completed the ride at a mean speed of 144 m/minute (slow group). Immediately after the ride the fast group of horses had higher packed cell volume, haemoglobin, neutrophils and lower lymphocyte counts than the slow...
White SL, Williamson LH, Maykuth PL, Cole SP, Andrews FM.The exercise intensity of horses competing in 3-day combined training events at 3 different levels of competition (CCI, n = 7; CCI, n = 11; CCI, n = 23) was investigated. Environmental conditions during all events were cool with 100% cloud cover. Heart rates were continuously recorded at 5 s intervals by a heart rate monitor. Mean +/- s.d. heart rate for all horses during each phase were: Phase A = 118 +/- 11 beats/min, Phase B = 179 +/- 22.7 beats/min, Phase C = 129 +/- 13.9 beats/min and Phase D = 174 +/- 19.6 beats/min. Mean +/- s.d. heart rates on Phase A and C were significantly different...
Schroter RC, Marlin DJ.This study provides an objective method for estimating the oxygen consumption of horses while running on variable slopes so that realistic comparisons may be made of the locomotory transport cost involved in 3-day events, particularly the Speed and Endurance Test, at sites of differing terrain. A knowledge of the work profile over a particular course would enable competitors to plan speed and interval times appropriately along its length. We have developed a semi-empirical, but mechanistically based, model to calculate the oxygen cost of transport [COTpath in ml O2/kg/m path] for running on th...
Rajão MD, Leite CS, Nogueira K, Godoy RF, Lima EMM.The aim of this study was to understand the bone response against the exercise adaptations to reduce the occurrence of orthopedic injuries in endurance horses. To this end, the objective of the present work was to investigate how the bone adaptation on adult equines that were trained for 4-5 yr to endurance races responds to the long-term exercise of moderate intensity by comparing to non-athlete horses. For this purpose, 14 Arabian horses were selected and divided equally into two groups; a control group formed by animals that had never practiced physical activity nor been tamed and an exerci...
Sampieri F, Schott HC, Hinchcliff KW, Geor RJ, Jose-Cunilleras E.There is no evidence that use of oral electrolyte pastes enhances performance in competing endurance horses. Objective: To ascertain whether oral administration of a high dose (HD) of sodium chloride (NaCl) and potassium chloride (KCl) to endurance horses would differentially increase water intake, attenuate bodyweight (bwt) loss and improve performance when compared to a low dose (LD). Methods: A randomised, blinded, crossover study was conducted on 8 horses participating in two 80 km rides (same course, 28 days apart). Thirty minutes before and at 40 km of the first ride 4, horses received o...
Tarancón I, Armengou L, Melendez-Lazo A, Pastor J, Ríos J, Jose-Cunilleras E.To assess the prevalence of exercise-induced pulmonary hemorrhage (EIPH) among elite endurance horses after competition in a long-distance race. 20 endurance horses and 12 nonexercised or minimally exercised age-, breed-, and trainer-matched horses from the same environment (control horses). Bronchoalveolar lavage fluid samples collected from endurance horses at 3 to 8 days (sample A) and 36 to 38 days (sample B) after the race (100 km in 1 day [n = 3], 70 km/d for 2 days [12], or 100 km/d for 2 days [5]) were cytologically examined for the presence of hemosiderophages. Samples from control ho...
Raidal SL, Rose RJ, Love DN.In this study, the effects of prolonged, high intensity training on aspects of peripheral blood and bronchoalveolar lavage (BAL)-derived leucocyte function were evaluated in 8 horses. All horses undertook a 7 week endurance training programme, followed by 5 weeks of high intensity training (HIT). Thereafter, horses were divided into control (C) and overtraining (OT) groups. The frequency and intensity of training were increased more substantially for horses in the OT group. Training was terminated in week 32 when horses in the OT group demonstrated a significant performance reduction. Peripher...
White SL.Horses competing in 3-day, combined-training events develop a metabolic acidosis that is partially compensated for by a respiratory alkalosis immediately after phases B and D. By the end of phase C and 30 minutes to 2 hours after phase D, the acidosis is resolved by the oxidation of lactate, and a metabolic alkalosis prevails. A reduction in TBW and cation content occurs, which often is not replenished 12 to 24 hours after the event, even though the serum or plasma concentration of various constituents may be within normal limits. Hypochloremia and hypocalcemia, however, may persist 12 or more...
Hinchcliff KW, Kohn CW, Geor R, McCutcheon LJ, Foreman J, Andrews FM, Allen AK, White SL, Williamson LH, Maykuth PL.We examined the effects of participation in each of 3 modifications of Day 2 of a 3-day-event on blood and serum variables indicative of hydration, acid:base status and electrolyte homeostasis of horses. Three groups of horses - 8 European (E) horses and 2 groups each of 9 North American horses performed identical Days 1 (dressage) and 3 (stadium jumping) of a 3-day-event. E horses and one group of the North American horses (TD) performed modifications of Day 2 of a 1 Star 3-day-event and the other group of North American horses (HT) performed a Horse Trial on Day 2. Jugular venous blood was c...
Physick-Sheard PW.The quality of the overall response to exercise in the horse is very similar to that seen in man and laboratory animals; differences are mainly quantitative and persist when relative body weight is taken into account. The apparently greater flow capacity of the equine muscle bed during maximal whole-body exercise implicates the extent of central circulatory adaptations as the limiting factor in performance but implies a role for increase in arteriolar capacitance/muscle capillarity as an appropriate response to intense endurance training. The blood oxygen-carrying capacity of the horse is ofte...
Hess TM, Kronfeld DS, Williams CA, Waldron JN, Graham-Thiers PM, Greiwe-Crandell K, Lopes MA, Harris PA.To compare effects of oral supplementation with an experimental potassium-free sodium-abundant electrolyte mixture (EM-K) with that of oral supplementation with commercial potassium-rich mixtures (EM+K) on acid-base status and plasma ion concentrations in horses during an 80-km endurance ride. Methods: 46 healthy horses. Methods: Blood samples were collected before the ride; at 21-, 37-, 56-, and 80-km inspection points; and during recovery (ie, 30-minute period after the ride). Consumed electrolytes were recorded. Blood was analyzed for pH, PvCO2, and Hct, and plasma was analyzed for Na+, K+,...
Fielding CL, Meier CA, Fellers GK, Magdesian KG.OBJECTIVE To compare results of point-of-care laboratory testing with standard veterinary clinical examination findings at a single time point during endurance competition to identify horses at risk for elimination. ANIMALS 101 endurance horses participating in the 2013 Western States 160-km (100-mile) endurance ride. PROCEDURES At the 58-km checkpoint, blood samples were collected from all horses. Samples were analyzed for pH, Pco2, base excess, anion gap, PCV, and whole blood concentrations of sodium, potassium, chloride, total carbon dioxide, BUN, glucose, and bicarbonate. Corrected electro...
Mukai K, Ohmura H, Takahashi Y, Kitaoka Y, Takahashi T.We investigated whether horses trained in moderate and mild hypoxia demonstrate greater improvement in performance and aerobic capacity compared to horses trained in normoxia and whether the acquired training effects are maintained after 2 weeks of post-hypoxic training in normoxia. Seven untrained Thoroughbred horses completed 4 weeks (3 sessions/week) of three training protocols, consisting of 2-min cantering at 95% maximal oxygen consumption under two hypoxic conditions (H16, F O = 16%; H18, F O = 18%) and in normoxia (N21, F O = 21%), followed by 2 weeks of post-hypoxic traini...
Aguilera-Tejero E, Estepa JC, López I, Bas S, Garfia B, Rodríguez M.To evaluate changes in plasma ionized calcium (Ca2+) and parathyroid hormone (PTH) concentrations in horses competing in endurance rides. Methods: Longitudinal clinical study. Methods: 28 horses. Methods: Venous blood samples were obtained from horses before and after racing 80 km. Plasma pH and concentrations of Ca2+, PTH, inorganic phosphorus, albumin, lactate, and magnesium were measured. Results: Overall, a significant decrease in mean (+/- SD) plasma Ca2+ concentration (from 6.44 +/- 0.42 to 5.64 +/- 0.42 mg/dl) and a significant increase in plasma PTH concentration (from 49.9 +/- 30.1 to...
Sauer FJ, Bruckmaier RM, Ramseyer A, Vidondo B, Scheidegger MD, Gerber V.The aims of this study were to better characterize the adrenal response to i.v. adrenocorticotropic hormone (ACTH) in horses with and without gastric disease and to validate and simplify the ACTH stimulation test by determining the diagnostic accuracy of six consecutive sampling time points after ACTH administration for equine glandular gastric disease (EGGD) and equine squamous gastric disease (ESGD). Twenty-six endurance and eventing horses without clinical disease [Sport Horse Population (SHP)] and an independent population of 62 horses [General Population (GP)] were grouped by gastroscopic...
Boucher JH, Ferguson EW, Wilhelmsen CL, Statham N, McMeekin RR.The erythrocytes of 14 conditioned horses participating in a 157-km endurance ride (requiring 14-21 h) were examined before the ride, immediately upon entering the 44-91-, and 130-km rest stops, and at the finish. At the first rest stop (44 km), the mean erythrocyte count increased 41% (P less than 0.001), the mean hematocrit (Hct) increased 30% (P less than 0.001) and the mean hemoglobin (Hb) increased 33% ( P less than 0.001). Although subsequent mean erythrocyte counts, Hct, and Hb values remained significantly elevated above controls, the values decreased 9-9% from the 4-km values later in...
Essén-Gustavsson B, Jensen-Waern M.Glycogenolysis and lipolysis are essential for energy production in muscle during prolonged exercise but less is known about the role of amino acid metabolism. The aim was to study the effect of an endurance race on pro- and macroglycogen, triglycerides and amino acid concentrations in muscle and on selected blood parameters, especially the amino acid response in the blood during the recovery phase. Seven endurance-trained horses completed a race covering 100-120 km. Blood samples were collected one day before the race, after the finish and 1 and 8 days after the race. Needle biopsy specimens ...
Rivero JL, Serrano AL, Quiroz-Rothe E, Aguilera-Tejero E.The objective of this study was to investigate the relationship between kinematic variables and muscle characteristics by determining (1) if heavy endurance training alters these variables and (2) if such modifications occur in a coordinated manner. Fifteen Andalusian stallions age 41-45 months were used. Five horses were used as controls and 10 horses underwent a training programme based on aerobic exercise for 8 months. Intensity of exercise was adjusted individually for each horse according to a standardised exercise test. Stride kinematic characteristics at the trot were analysed by videog...
Goachet AG, Julliand V.Measurements of respiratory exchanges in genuine exercise conditions are undoubtedly of interest to further define the energy needs of endurance horses. However, the equine K4b2, the gas exchanges portable device validated for equines, has not been used in Arabian endurance horses yet. Therefore, the objective of this study was to implement field cardio-respiratory measurements in such horses using the equine K4b2 in order to assess energy expenditure (EE). Measurements of heart rate (HR), oxygen uptake (VO2), carbon dioxide production (VCO2), respiratory frequency (RF), tidal volume (VT) and ...
Rose RJ, Hodgson DR.Eleven horses were studied throughout a 12 week training schedule. Serial blood samples were taken for haematological analysis and an extensive biochemical profile, including the following parameters: sodium, potassium, chloride, bicarbonate, glucose, creatinine, urea, bilirubin, iron, total protein, albumin, alkaline phosphatase, aspartate aminotransferase, creatine kinase, gamma glutamyl transferase, calcium phosphate and cholesterol. There were few significant changes detected and it was concluded that routine haematological and biochemical screening has no useful role in assessing the fitn...
Smith JE, Barnes AL, Maloney SK.Body temperature can be a useful measure of how well the horse responds to thermal challenges of exercise and environment. Currently there is little information available about how body temperature changes throughout an endurance ride, and no nonsurgical methods to evaluate internal temperature of exercising horses during prolonged periods and during long distances. Objective: To develop and test a nonsurgical method, using temperature loggers, of continuously recording internal temperature during exercise and over an extended period. Methods: Loggers were inserted transcervically into the ute...
Lucke JN, Hall GN.Blood samples were taken before and immediately after 80 km and 40 km rides held on consecutive days and analysed for haematocrit, blood glucose and lactate, plasma sodium, potassium, calcium, albumin, free fatty acids (FFA), glycerol, bicarbonate, insulin, cortisol, glucagon, urea, creatinine, uric acid, bilirubin and alkaline phosphatase. Unusually hot weather probably contributed to haemoconcentration with a significant (P < 0.001) increase in haematocrit and plasma albumin. A fall in blood glucose, with a rise in FFA and glycerol were consistent with long distance riding and were associ...
Holbrook TC, McFarlane D, Schott HC.The inflammatory and neuroendocrine response to endurance exercise and relationship of these parameters to performance is not well documented in horses. HYPOTHESES OR OBJECTIVES: Evidence of systemic inflammation is associated with poor performance in horses competing in endurance events. Methods: Blood was collected prior to and at the finish or elimination point from horses competing in both the 80 and 160 km American Endurance Ride National Championship competitions in 2006. Immunoreactive alpha-melanocyte stimulating hormone (α-MSH) and tumour necrosis factor-alpha (TNF-α) were quantifie...
Bollinger L, Bartel A, Weber C, Gehlen H.High elimination rates and concerns for horse welfare are important issues in endurance riding. Improved understanding of the causes of elimination could increase completion rates in this sport. We have identified pre-ride laboratory risk factors that enable an assessment of potential elimination before the ride. A longitudinal cohort study was performed among 49 healthy horses competing in the 160 km endurance ride at the 2016 World Championship of Endurance Riding in Samorin/Slovakia. Blood samples were taken before the event. For statistical evaluation, horses were categorized into three gr...
Barton MH, Williamson L, Jacks S, Norton N.To determine plasma endotoxin concentration in horses competing in a 48-, 83-, or 159-km endurance race and its importance with regard to physical, hematologic, or serum and plasma biochemical variables. Methods: 3 horses. Methods: Weight and rectal temperature measurements and blood samples were obtained before, during, and after exercise. Blood samples were analyzed for plasma endotoxin concentration; serum antiendotoxin antibody titers; thromboxane B2 (TxB2) and 6-keto-prostaglandin F1alpha (PGF1alpha) concentrations; tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) activitie...
Rose RJ, Ilkiw JE, Sampson D, Backhouse JW.Sixteen horses competing in a three-day event had venous blood samples collected during the speed and endurance test (day 2) to examine changes in blood gas ands acid-base balance, and the concentrations of lactate, pyruvate, beta-hydroxybutyrate, acetoacetate, alpha-ketoglutarate and cortisol. Following the roads and tracks and steeplechase phases there was a significant metabolic and respiratory alkalosis despite a rise in lactate. After completion of the cross country section, although there was a significant decrease in total base, there was no significant change in pH from pre-event value...
