Horse training involves the systematic process of teaching horses specific behaviors and skills to enhance their performance and manageability. This process encompasses a variety of techniques and methods tailored to the individual horse's temperament, age, and intended use, such as riding, racing, or working. Training regimens aim to develop desired traits such as obedience, agility, and endurance while ensuring the horse's physical and mental well-being. This page compiles peer-reviewed research studies and scholarly articles that explore various aspects of horse training, including methodologies, behavioral outcomes, and the impact on equine welfare and performance.
Colahan PT, Kollias-Bakert C, Leutenegger CM, Jones JH.Physical exertion is a stimulus for the upregulation of cytokine production including IL-1beta, IL-1ra, IL-2, IL-4, IL-6, IL-10 and TNF-alpha in horses. To investigate that hypothesis, we initiated training of 5 stall-rested Thoroughbreds. Blood samples were drawn before and weekly during training. The relative transcription of mRNA within the leucocytes was measured using real time TaqMan quantitative PCR. The training protocol was walking (3 min), trotting (3 min) and cantering/galloping (6 min) increasing in intensity weekly (6 to 12 m/s) and culminating in an intense exercise period. Compa...
Young LE, Marlin DJ, Deaton C, Brown-Feltner H, Roberts CA, Wood JL.Maximum oxygen uptake also appears to correlate to athletic performance in horses. In the Thoroughbred industry, there has long been an empirical theory that heart size is related to athletic performance, despite a lack of scientific evidence supporting this assertion. To investigate the relationship between peak oxygen consumption (VO2max) and cardiac size measured by echocardiography, guided M-mode and 2-dimensional echocardiography were performed in 17 conditioned Thoroughbreds with a range of VO2max from 126 to 217 ml/min/kg STPD (mean +/- s.d. 158 +/- 28 m/min/kg). Horses were age 2-10 ye...
McDonough P, Kindig CA, Ramsel C, Poole DC, Erickson HH.In healthy man, conditions that change muscle O2 delivery affect the achievable maximum rate of O2 uptake as well as the metabolic (e.g. lactate threshold, LT) and gas exchange (e.g. gas exchange threshold, Tge) responses to incremental exercise. Inclined (I) compared to level (L) running increases locomotory muscle EMG at a given speed in the horse, indicative of elevated metabolic demand. To our knowledge, the effect of treadmill incline on VO2,max, LT and Tge has not been addressed in the exercising quadruped. We used blood sampling and breath-by-breath expired gas analysis to test the hypo...
Rabuffo TS, Orsini JA, Sullivan E, Engiles J, Norman T, Boston R.To determine associations between age, sex, or medical treatment and prevalence and severity of gastric ulceration in Standardbred racehorses in training. Methods: Cross-sectional study. Methods: 224 Standardbred racehorses in training. Methods: Gastroscopy was performed on each horse, and mucosal ulceration was graded from 0 (normal mucosa, no lesions) to 3 (extensive, often coalescing, lesions with areas of deep ulceration). Associations between age, sex, or treatment and prevalence and severity of ulcers were evaluated. Results: Prevalence of gastric ulceration was 87%. Although there was l...
Pinchbeck GL, Clegg PD, Proudman CJ, Morgan KL, Wood JL, French NP.We identified risk factors associated with falling during steeplechase racing. We used retrospective data from all steeplechase runs on UK racecourses during 1999: 10,866 starts with 647 horse falls. The relationship between continuous variables and falling was assessed using generalised additive models (GAMs). Polynomial fits then were included in a multilevel, multivariable logistic-regression model. The number of runners had a linear, positive association with the risk of falling. The distance of the race had a non-linear relationship with the risk of falling; the risk steadily increased in...
Van Eenoo P, Delbeke FT, Deprez P.Clenbuterol, a beta-adrenergic agonist, is used in the treatment of recurrent airway obstruction in horses. It is prohibited by horse racing authorities, because of its stimulating and growth-promoting properties. However, information on detection times of clenbuterol after administration by nebulization is lacking. In this study, a fast, sensitive quantitative GC-MS(2) method for the detection of clenbuterol in urine was developed. Alkaline liquid-liquid extraction was followed by derivatization to a cyclic methyl boronate derivative and analysis on a Finnigan MAT GCQ instrument. Method valid...
Yamano S, Eto D, Sugiura T, Kai M, Hiraga A, Tokuriki M, Miyata H.To determine the effect of growth and training on metabolic properties in muscle fibers of the gluteus medius muscle in adolescent Thoroughbred horses. Methods: Twenty 2-year-old Thoroughbreds. Methods: Horses were randomly assigned to 2 groups. Horses in the training group were trained for 16 weeks, and control horses were kept on pasture without training. Samples were obtained by use of a needle-biopsy technique from the middle gluteus muscle of each horse before and after the training period. Composition and oxidative enzyme (succinic dehydrogenase [SDHI) activity of each fiber type were de...
Back W, Schamhardtt HC, Barneveld A, van Weeren PR.Nowadays, ponies are used more and more for competitive equine sports, driving and racing. The locomotor performance of ponies, however, has been evaluated in only a few kinematic and kinetic studies. To compare the longitudinal development of locomotor characteristics in the pony to the same process in the horse, the kinematics of 23 Shetland ponies were recorded at the trot on a treadmill (3 m/s) at ages 4 and 30 months using a modified CODA-3 apparatus. Furthermore, the influence of specific feeding and training regimes on this development was evaluated. It appeared that stride and stance d...
Hillyer MH, Taylor FG, Proudman CJ, Edwards GB, Smith JE, French NP.A case control study was performed to identify risk factors for colic caused by simple colonic obstruction and distension (SCOD) in the horse. Case horses were recruited from 2 veterinary school clinics. Control horses were population based and matched by time of year. A number of risk factors were considered in the following areas: general carer and premises information; exercise information; husbandry information (housing- and pasture-related); feeding information; breeding information; behavioural information; travel information; preventive medicine information and previous medical informat...
Tenenbaum G, Lloyd M, Pretty G, Hanin YL.A study was carried out to examine the ability of equestrians to accurately report precompetition emotions and thoughts across varying time delays (3,7, and 14 days) after competition. Forty male and female dressage riders were randomly divided into two equal groups: participants who watched their videotaped precompetition routine before responding to the items, and participants who visualized the precompetition routine without any external aid. Each rider completed several questionnaires which measured emotions, items related to horses, and an open-ended question on thoughts and emotions at t...
Chateau H, Degueurce C, Jerbi H, Crevier-Denoix N, Pourcelot P, Audigié F, Pasqui-Boutard V, Denoix JM.The objective of this study was to assess the effects of asymmetric placement of the foot on the three-dimensional motions of the interphalangeal joints. Four isolated forelimbs were used. Trihedrons, made of three axes fitted with reflective markers, were screwed into each phalanx. They allowed to establish a local frame associated with each bone and thus to define the spatial orientation of the phalanges. The limbs were then placed under a power press, and subjected to compression with gradually increasing force (from 500 to 6 000 N). The procedure was performed in neutral position and with ...
Bachmann I, Staﾬher M.Out of a representative sample of 1861 Swiss horse yards, 622 horse keepers (35.2%) with 2536 horses, ponies and donkeys sent back a questionnaire about general farm characteristics, their horse-specific training, horse stock, housing conditions, intraspecific social contacts, feeding, ability to move freely, use of the horses and management. 83.5% of horses were kept individually (thereof 18.3% tethered, 32.3% in a loose box indoors, 28.4% in a loose box outdoors, and 4.5% in a loose box with permanent access to a paddock or an individual pasture), and 16.5% lived in group housing systems. 36...
Isenbügel E.Over 45 million years of evolution the horse developed to a highly specialized animal in anatomy, physiology and behavior. No other animal had influenced the economic and cultural history of men to such extent. Hunting prey since the ice age, domesticated 4000 B.C. and used for thousands of years as unique animal all over the world has attained a new role today as partner in sport, as companion animal and even as cotherapeutic. The well known behavioral demands in use and keeping are still often not fulfilled.
Caron JP, Peters TL, Hauptman JG, Eberhart SW, Orth MW.To determine the effects of orally administered glucosamine on concentrations of markers of bone and cartilage metabolism in Standardbred horses during race training. Methods: Twenty 16- to 20-month-old Standardbreds beginning race training. Methods: Horses were randomly assigned to 2 groups. One group received glucosamine hydrochloride (4 g, PO, q 12 h), and the second (control) group received glucose (4 g, PO, q 12 h). Serum samples were obtained prior to onset of the study (baseline) and at regular intervals for 48 weeks for determination of concentrations of keratan sulfate (KS), osteocalc...
Hamlin MJ, Shearman JP, Hopkins WG.Various changes in physiological parameters are associated with overtraining, which can be a serious problem for human and equine athletes. A 34 week longitudinal study was conducted to investigate the effects of an acute training overload on physiological parameters in 10 Standardbred racehorses. After 24 weeks of training, horses received 8 weeks of increased workload, followed by 2 weeks recovery. Horses performed a 2400 m time trial and a progressive submaximal exercise test on alternate weeks. By the end of the heavy training period, the average time for the final 1200 m of the time trial...
Shearman JP, Hamlin MJ, Hopkins WG.Human athletes taper or reduce their training load before a race to enhance performance, apparently because recovery from the effects of fatigue occurs faster than the loss of fitness from the reduced training. However, there appear to be no previous studies of tapering of equine athletes. Our aim in the present study was, therefore, to investigate the efficacy of tapering with Standardbred pacers. We determined the effect of repeated cycles of tapered training on performance of Standardbred pacers. After 8 weeks of jogging and 3 x 2 week cycles of pace work, 19 horses were randomised to a tap...
Szalay F, Back W, Barneveld A, Schamhardt H, Hajós F.A VHS video--computer-based image analysis combination is described as a low sampling rate motion analysis system. Video recordings were taken indoor without any artificial illumination at 25 fps sampling rate. The horse studied was running on a high-speed treadmill and observed at 1.6, 4 and 7 m/s velocities at walk, trot and canter, respectively. Left forelimb and hindlimb were recorded separately from lateral view. For comparison, parallel CODA-3 recordings were taken at the same time from the same position. Joint angles were expressed and compared in angle-time diagrams. Sampling of both s...
Dart AJ, Cries L, Jeffcott LB, Hodgson DR, Rose RJ.To evaluate the effect of a commercially available 25% propylene glycol hydrogel preparation (Solugel; Johnson and Johnson Medical, North Ryde, Australia) on healing of full-thickness skin wounds on the distal aspect of the limb in horses. Methods: Experimental. Methods: Eight Standardbred horses. Methods: Standardized (2.5 x 2.5 cm) full-thickness skin wounds were created over the mid-dorsomedial aspect of both metacarpi in 8 horses. One wound in each horse was dressed with saline solution (0.9% NaCl) soaked gauze, and one was treated with Solugel under dry regular gauze; wounds were then ban...
Kearns CF, McKeever KH, Kumagai K, Abe T.This study examined whether body composition was predictive of competitive success in elite standardbreds (STB). Rump fat and muscle thickness (MTH) (vastus lateralis/intermedius [VL], extensor carpi radialis [ECR]) were measured in vivo in male n=6; female n=8 by B-mode ultrasound. Percentage body fat (%fat) was calculated from rump fat. There were no gender differences for age, body mass (males 432+/-11 kg; females 443+/-13 kg), fat-free mass (FFM) (males 400+/-12 kg; females 400+/-11 kg), ECR MTH (males 61+/-2 cm; females 60+/-2 cm) or race time (RT) (males 113+/-3 s; females 114+/-2 s). Ma...
Arai T, Hosoya M, Nakamura M, Magoori E, Uematsu Y, Sako T.The activities of the enzymes involved in the malate-aspartate shuttle and m RNA expression of malate dehydrogenase (MDH), a crucial enzyme for the NADH shuttle that produces ATP in glucose metabolism in the peripheral leukocytes of horses, were measured to investigate the change in metabolic states with training. There were no significant differences in plasma glucose and immunoreactive insulin concentrations between race horses and riding horses, used as a comparable reference. The cytosolic and mitochondrial MDH activities in leukocytes of race horses were significantly higher than those of...
Okumura M, Kim GH, Tagami M, Haramaki S, Fujinaga T.Keratan sulphate (KS) concentration in sera from resting horses and horses training daily on a racetrack was measured by an inhibition enzyme-linked immunosorbent assay (ELISA) using anti-equine KS antibody 1/14/16H9. For the in-training horses, serum KS concentrations in 2-year-old-horses was significantly higher than 3- or 4-year-old-horses. A higher concentration of serum KS was found in the in-training group than in the long-term resting group in 2-year-old-horses. Serum KS concentration increased remarkably immediately after training in healthy horses, and at 1, 5, 9 and 24 h after traini...
Visser EK, van Reenen CG, van der Werf JT, Schilder MB, Knaap JH, Barneveld A, Blokhuis HJ.Forty-one Dutch Warmblood immature horses were used in a study to quantify temperamental traits on the basis of heart rate (HR) and heart rate variability (HRV) measures. Half of the horses received additional training from the age of 5 months onwards; the other half did not. Horses were tested at 9, 10, 21 and 22 months of age in a novel object and a handling test. During the tests, mean HR and two heart variability indices, e.g. standard deviation of beat-to-beat intervals (SDRR) and root mean square of successive beat-to-beat differences (rMSSD), were calculated and expressed as response va...
Dougherty DM, Lewis P.Using three horses we imvestigated responding on several concurrent variable-interval schedules. Each horse was first trained, using the method of successive approximations, to press a response lever with its upper lip. Following successful acquisition of the lip-press response, horses spent several days on pretraining schedules. These included a continuous reinforcement schedule and three variable-interval concurrent schedules: VI 15-sec VI 15-sec, VI 30-sec VI 30-sec, and VI 45-sec VI 45-sec. Horses were then exposed to the experimental sessions; sessions were conducted daily in the horse's ...
The Journal of heredityJuly 1, 1976
Volume 67, Issue 4 247-248 doi: 10.1093/oxfordjournals.jhered.a108721
Field JK, Cunningham EP.In an analysis of handicap ratings of 1158 3-year-old thoroughbred racehorses, estimates were obtained for the effects of sex differences, the correlation between mates, the effectiveness of selection in males and females, and the heritability of racing performance. The results agreed closely with those of a previous study, and indicated a heritability of about 0.35 to 0.40, some assortative mating, and highly effective selection for performance.
Gehlen H, Marnette S, Rohn K, Kreienbrock L, Stadler P.Echocardiographic measurements have to be reliable and reproducible with only a low day to day variability for detecting pathological changes of left ventricular myocardial function in horses. The day dependent fluctuation margin represents an important indicator for the reproducibility of a method. To find out the day to day variability of echocardiographic parameter in healthy warmblood horses, in the present study repeated echocardiographic measurements at three consecutive days were carried out (at the same time and by the same examiner) at 11 untrained and 7 trained warmblood horses. The ...
Hall Angerås M.In Sweden equestrian sport activities are the sixth most popular sport and predominantly women and girls are engaged. Horses are prey animals and humans are predators, and the two species therefore act in completely different ways. It is well known that accidents can occur when horses and humans interact. Literature from different countries in the world reveals that most accidents happen to females and also children are at risk. The most common accident is when a rider falls from a horse, but also unmounted humans are at risk for injuries. Most of the injuries are uncomplicated, but there are...
Smyth GB.A 3-year-old Thoroughbred filly examined because of poor performance after a fall was found to be ataxic. Radiography revealed a linear defect in the right dorsal cranial articular facet of the fifth cervical vertebra. The defect was thought to be a fracture or a developmental defect. Arthrodesis and stabilization were achieved by ventral implantation of a Bagby basket in the articulation between the fourth and fifth cervical vertebrae. The ataxia resolved within 4 months, and the filly was able to resume full race training.
Ljungvall K, Ronéus B.To describe the injuries in the middle carpal joint of trotting Standardbred racehorses in relation to future racing and to review the use of synovectomy in clinical cases. Methods: Review of medical records and racing statistics of clinical cases. Results: Sixty-six percent of horses undergoing arthroscopic surgery of the middle carpal joints returned to racing, but there were only weak associations between future racing success and findings at surgery. Lesions in the middle carpal joint were similar to what have previously been described, but there were no recorded injuries to the intermedia...
Munoz-Nates F, Chateau H, Van Hamme A, Camus M, Pauchard M, Ravary-Plumioen B, Denoix JM, Pourcelot P, Crevier-Denoix N.The repetitive impulsive loading resulting from foot and
ground interaction in the initial part of the stance phase
is often mentioned as a source of risk of developing
subchondral bone damage leading to osteoarthritis, both
in man and horses. Because of the high frequency of this
phenomenon, called the impact shock, accelerometry is
the preferred method to measure it. In the horse, measurement of the hoof ’s vertical deceleration at impact
has been shown to be a useful method for comparing
different track surfaces. However, accelerometric studies
comparing surfaces in trotters at h...
ter Braake F, Hesselink JW, Jonker FH.An eleven year old warmblood mare was referred to Dierenkliniek Emmeloord because of recurrent cyclic behavioral problems. A standing bilateral laparoscopic ovariectomy was performed. Due to this minimal invasive technique a quick return to training was possible.
Rossdale PD.The place of clinical research in the veterinary profession is discussed against the author's personal experiences and in the context of how research workers, clinicians, teachers and veterinary students might be brought into a more cohesive unit through the development of a Faculty of clinical research and experimental medicine. It is argued that students should receive training in research and teaching and that efforts should be made to break down the attitude of "them" and "us" which tends to separate the clinicians and academics.
Freeman DW, Potter GD, Schelling GT, Kreider JL.Nitrogen metabolism was measured in five mature geldings performing varying levels of work that simulated race training. Following an initial maintenance period without forced exercise, workload was increased in succeeding 18-d periods by doubling the distance the horses were galloped in each period from period 2 through 4. A 4-d N balance experiment was conducted at the end of each 18-d period. The maximum distance galloped daily, which was in period 4, was repeated in period 5. Then, workloads were decreased through period 7. Nitrogen balance was determined in two additional periods, 8 and 9...
Ostermeier S, Palme R, Vervuert I, Glomm B, Feige K, Macho-Maschler S, König von Borstel U, Venner M.In this study, gastroscopy was performed twice in 31 two-year-old Thoroughbred racehorses in training. Salivary cortisol (SC) and fecal cortisol metabolite (FCM) concentrations were determined to measure the stress impact. One gastroscopy was performed at the beginning and one six months later at the end of the horses' first training season. According to the Wilcoxon signed rank test, a mild but significant increase of SC (1st gastroscopy: = 0.0045, 2nd gastroscopy: < 0.0001) and FCM (1st gastroscopy: < 0.0001, 2nd gastroscopy: = 0.0006) values after gastroscopy compared to basal val...
Cameron-Whytock HA, Parkin TDH, Hobbs SJ, Brigden CV, Bennet ED.Equestrian eventing is a dangerous Olympic sport, with 16 rider and 69 horse fatalities at competition in the last 10 years. Despite this, there is limited research that aims to improve safety within the sport. Objective: The purpose of this study was to identify risk factors for horse falls, which are the leading cause of rider fatality within the sport. Methods: Retrospective cohort study. Methods: Competition data between January 2005 and December 2015 were analysed. Descriptive statistics followed by univariable logistic regression to identify risk factors for inclusion in a multivariabl...
Ralston SL.Equine teaching and research programs are popular but expensive components of most land grant universities. External funding for equine research, however, is limited and restricts undergraduate research opportunities that enhance student learning. In 1999, a novel undergraduate teaching and research program was initiated at Rutgers University, New Brunswick, NJ. A unique aspect of this program was the use of young horses generally considered "at risk" and in need of rescue but of relatively low value. The media interest in such horses was utilized to advantage to obtain funding for the program...
Pearson W.Standardbred trainers from 1 racetrack and 7 off-track training facilities were surveyed to determine the most common drugs, and prevalence of concurrent herb administration. Furosemide (on-track) and anti-inflammatory drugs (off-track) were the most common drugs administered. Among horses on-track, 9.8% received herbs compared with 13.8% off-track horses; 67% and 58% of these horses, respectively, received concurrent drugs. Les soigneurs de Standardbreds de 1 piste de course et de 7 installations d’entraînement hors piste ont été interrogés afin de déterminer les médicaments les plus...
Preston SA, Brown MP, Chmielewski TL, Trumble TN, Zimmel DN, Hernandez JA.To determine the effects of yearling sale purchase price, exercise history, lameness, and athletic performance (speed) on purchase price of 2-year-old in-training Thoroughbreds and to compare the distance exercised within 60 days prior to 2-year-old in-training sales between horses with high yearling sale purchase prices versus those with low yearling sale purchase prices and between horses with lameness during training and those without lameness during training. Methods: Prospective study. Methods: 51 Thoroughbreds. Methods: Thoroughbreds purchased at a yearling sale were trained prior to res...
Geor RJ, McCutcheon LJ, Shen H.The objectives of this study were to determine the effects of 10 consecutive days of moderate-intensity training on 1) the muscular metabolic response to exercise at 100% of the pre-training maximum rate of oxygen consumption (VO2max); and 2) mitochondrial enzyme markers (citrate synthase, CS; succinate dehydrogenase, SDH; 3-hydroxy-acyl-CoA dehydrogenase, HAD) of oxidative capacity in middle gluteal muscle. Six mature, unfit Thoroughbred horses completed both incremental (for determination of VO2max) and high-intensity exercise protocols before (HI1) and after (HI2) training. Training consist...
Palmer S, Gomez AMM, Mohammed HO.A longitudinal retrospective study was carried out to investigate the attrition of Thoroughbred (TB) and Standardbred (SB) horses racing at New York racetracks during the 2016 to 2019 seasons. The data were collected from the New York State Gaming Commission (NYSGC) Equine Breakdown, Death, Injury and Incident (EBDII), The Jockey Club InCompass Solutions, and The United States Trotting Association Pathway databases. Survival analysis was used to compare the predisposing factors by breed of the horse. The study included 431 horses (360 TB and 71 SB). There was a significant difference between t...
Sampson SN, Tucker RL, Bayly WM.We evaluated the relationships of heart score (HS) and echocardiographic measures to maximal oxygen consumption (VO2max), maximal cardiac output (Qmax), and maximal stroke volume (SVmax). Six fit, mature Thoroughbred horses weighing (mean +/- s.e.) 487 +/- 11 kg were run 4 times on an inclined (10%) treadmill. Each run consisted of a 3 min warm-up at 4 m/s followed by completion of an incremental exercise test in which each horse ran until VO2max was reached. Arterial and mixed venous blood was collected to determine arteriovenous oxygen content difference C(a-v)O2[ in the last 15 s of exercis...
MacKechnie-Guire R, Fisher M, Mathie H, Kuczynska K, Fairfax V, Fisher D, Pfau T.Thermography is a non-invasive method for measuring surface temperatures and may be a convenient way of identifying hypo/hyperthermic areas under a saddle that may be related to saddle pressures. A thermal camera quantified minimum/maximum/mean temperatures at specific locations (left/right) of the thoracic region at three-time points: (1) baseline; (2) post lunging; (3) post ridden exercise in eight non-lame sports horses ridden by the same rider. A Pliance (Novel) pressure mat determined the mean/peak saddle pressures (kPa) in the cranial and caudal regions. General linear mixed models with ...
Lansade L, Calandreau L.The use of conditioned reinforcers is increasingly promoted in animal training. Surprisingly, the efficiency of their use remains to be demonstrated in horses. This study aimed to determine whether an auditory signal which had previously been associated with a food reward 288 times could be used as a conditioned reinforcer to replace the primary reinforcer in an unrelated operant conditioning procedure. Fourteen horses were divided into two groups of 7: No Reinforcement (NR) and Conditioned Reinforcement (CR). All horses underwent nine sessions of Pavlovian conditioning during which the word "...
Schott HC, Hinchcliff KW.A number of feeding and management practices, dietary electrolyte supplements, and medications may affect fluid and electrolyte status in resting and exercising horses. The contents of the gastrointestinal tract of the equine athlete, unlike its human counterpart, are responsible for more than 10% of body weight. Although ingesta traditionally has been considered dead weight for the sprinting horse, it is a valuable reservoir of fluid and electrolytes that may be used during endurance exercise. Numerous strategies for hyperhydration of the equine athlete and for replacement of fluid and electr...
Bowers J, Slocombe RF.To compare the effect of girth materials and commonly used girth tensions on athletic performance of race-horses and to test the length tension properties of commercially available girths. Methods: Seven horses were exercised at speeds to produce 95% of maximal heart rates on 15 occasions using a randomised block design, and girthed with 5 different girths at 3 nominal tensions of 6, 12 or 18 kg. The girths used were a standard elastic race girth, an 'American' elastic race girth, an elastic race girth twice the normal width, a standard canvas race girth and a canvas race girth at twice the no...
Rivero JL, Serrano AL.Three different myosin heavy chain (MHC) isoforms have been identified in the equine gluteus medius muscle: the slow or MHC-I and the 2 fast MHC-IIA and MHC-IIX isoforms. They are distributed in 3 fibre types containing a single MHC (I, IIA, IIX) and 2 hybrid types co-expressing 2 isoforms (I + IIA, IIA + IIX). The aim of this study was to determine if heavy carriage training alters skeletal MHC composition in horses. Fourteen Andalusian mares age 42-46 months were used. Seven horses were used as controls to estimate the effects of growth on muscle. The remaining 7 horses underwent a training ...
