Exercise physiology in horses involves the study of the physiological responses and adaptations of horses to physical activity. This field examines how exercise impacts various systems in the equine body, including the cardiovascular, respiratory, muscular, and metabolic systems. Researchers focus on understanding how these systems interact during different types and intensities of exercise, and how they contribute to performance and recovery. Key areas of interest include the assessment of aerobic and anaerobic capacity, muscle fiber composition, energy metabolism, and thermoregulation. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms of exercise physiology in horses, with an emphasis on performance optimization, training regimens, and the prevention of exercise-related disorders.
Colahan PT, Bailey JE, Chou CC, Johnson M, Rice BL, Jones GL, Cheeks JP.Twelve clinically sound, healthy, athletically conditioned Thoroughbred horses were subjected to an incremental exercise stress test to determine the effects and period of detection of a single dose of flunixin meglumine (1.1 mg/kg by intravenous injection) in serum and urine by ELISA. Flunixin concentrations, performance, and hematologic and clinical chemical parameters were measured. All horses were rotated through four treatment groups of a Latin-square design providing for each horse to serve as its own control. Flunixin meglumine reduced prostaglandin F(1alpha) and thromboxane concentrati...
The Journal of nutritionJune 4, 2002
Volume 132, Issue 6 Suppl 2 1622S-7S doi: 10.1093/jn/132.6.1622S
Marlin DJ, Fenn K, Smith N, Deaton CD, Roberts CA, Harris PA, Dunster C, Kelly FJ.Prolonged low-medium intensity exercise is associated with increased oxidative stress in humans. We hypothesized that competitive equine endurance racing would induce changes in circulatory antioxidants and produce systemic oxidative stress. Forty horses competing in a 140-km endurance race in warm conditions [shade temperature 15-19 degrees C; 62-88% relative humidity (%RH)] were sampled before (Pre), immediately after exercise (End) and at approximately 16 h into recovery (+16 h). Plasma ascorbic acid concentration was not different between Pre [11.1 (median); 4.6-20.3 micromol/L (range)] an...
Balogh N, Gaál T, Ribiczeyné PS, Petri A.Physical exercise in the horse induces a series of normal physiological and biochemical adaptations. Increasing metabolism and oxygen uptake may induce oxidative stress in various organs. The aim of this study was to examine exercise-induced changes in some plasma and RBC biochemical and antioxidant variables in pentathlon horses. Blood samples were taken from 14 horses before, immediately after, and 24 hours after competing in two 1-minute runs of intense exercise over jumps. The peak intensity periods were preceded by a 20-minute warm-up and separated by a 20-minute break. The following plas...
Kokkonen UM, Pösö AR, Hyyppä S, Huttunen P, Leppäluoto J.Previous data show that, in horses, plasma atrial natriuretic peptides (ANP and NT-ANP) remain elevated for a long time after exercise. To study whether exercise-induced changes in hormonal and fluid balance explain this, we measured plasma concentrations of COOH- and NH2-terminal atrial natriuretic peptides (ANP(99-129) and NT-ANP(1-98) together with arginine vasopressin (AVP), adrenocorticotrophin (ACTH), beta-endorphin, cortisol, catecholamines, and indicators of fluid balance in six Finnhorses after a graded submaximal exercise test on a treadmill. After exercise, AVP and catecholamines di...
McGowan CM, Posner RE, Christley RM.A questionnaire was used to determine the incidence of exertional rhabdomyolysis and the factors that might have contributed to its occurrence among 423 polo horses in 11 yards. The yards were selected at random, six of them with 111 horses, in north-eastern USA, and five with 312 horses in south-east England. During the 1999/2000 season the incidence of the condition was 7.3 per cent (9 per cent in the USA and 6.7 per cent in England). The incidence in mares was similar in the two countries, 8.4 per cent in the USA and 8.0 per cent in England, but the incidence in geldings in the USA (10 per ...
Voss B, Mohr E, Krzywanek H.The objectives of the present study were to investigate the effects of Aquatraining of horses (aqua-treadmill exercise; treadmill manufactured by Equitech - L.u.S. Equipment, Warendorf, Germany) on selected blood parameters [lactic acid concentration (mmol/l), haemoglobin content (g/l)] and on heart-rate variability (HRV) [heart rate (beats per min; b.p.m.), standard deviation of all NN-intervals (SDNN; ms), normalized power of the low and high frequency band (LFnorm, Hfnorm; au), % recurrence, % determinism and ratio(corr)]. Seven horses performed six exercise tests with different work loads ...
Moore JM, Timperio AF, Crawford DA, Burns CM, Cameron-Smith D.Jockeys are required to maintain very low body weight and precise weight control during competition. This study examined the weight loss and weight management strategies of professional horseracing jockeys in the state of Victoria, Australia. An anonymous, self-completed questionnaire was administered (55% response rate, n = 116). Almost half (43%) reported that maintaining riding weight was difficult or very difficult, with 75% routinely skipping meals. In preparation for racing, 60% reported that they typically required additional weight loss, with 81% restricting food intake in the 24 hours...
Butcher MT, Ashley-Ross MA.Fetlock joint kinematics during galloping in 2-, 3-, 4-, and 5-year-old Thoroughbreds in race training were quantified to determine if differences due to age could account for the observation that 2-year old Thoroughbred racehorses incur a high number of injuries to the bones and soft tissues in the distal forelimbs during training and at the outset of racing. Twelve Thoroughbred racehorses were videotaped in the sagittal plane at 250 frames/s during their daily galloping workout on a 7/8 mile sand-surface training track. Four galloping strides were recorded for each horse and subsequently dig...
Weishaupt MA, Hogg HP, Wiestner T, Denoth J, Stüssi E, Auer JA.To develop and validate a novel instrumented treadmill capable of determining vertical ground reaction forces of all 4 limbs simultaneously in horses. Methods: Data obtained while a horse was walking and trotting on the treadmill. Methods: 18 piezo-electric force transducers were mounted between the treadmill frame and supporting steel platform to measure the actual forces at the corresponding bearing points. Each of the 18 sensor forces is equal to the sum of the unknown hoof forces weighted with the transfer coefficients of the corresponding force application points. The 4 force traces were ...
Bröjer JT, Stämpfli HR, Graham TE.To determine proglycogen (PG) and macroglycogen (MG) content in equine skeletal muscle and to compare 2 analytical methods (acid hydrolysis [AC] and PG plus MG determination) for measurement of total muscle glycogen content (Gly(tot)) in biopsy specimens. Methods: Muscle biopsy specimens obtained from 41 clinically normal horses. Methods: Forty-five muscle biopsy specimens obtained from the middle gluteal (n = 31) or triceps (14) muscle were analyzed, using AC and MG plus PG determination for Gly(tot). Variability within muscle biopsy specimens for each method was calculated from duplicate ana...
Dingboom EG, van Oudheusden H, Eizema K, Weijs WA.In order to obtain broader insights into the equine musculoskeletal system, we studied the fibre type composition of 2 locomotory muscles in biopsies from Dutch Warmblood foals taken at 3 different ages in the first year postpartum. The muscle fibre types were determined histochemically as well as immunohistochemically. ATPase-characterised IIB fibres appear to express either IId or type lIa plus IId myosin heavy chain (MHC). A high percentage of fibres classified as IIA with ATPase expressed both fast types of MHC. The type I classification by the 2 methods matched almost completely. There wa...
Manohar M, Goetz TE, Humphrey S, Depuy T.It has been suggested that pulmonary injury and inflammation-induced histamine release from airway mast cells may contribute to exercise-induced arterial hypoxemia (EIAH). Because stress failure of pulmonary capillaries and EIAH are routinely observed in exercising horses, we examined whether preexercise administration of an H1-receptor antagonist may mitigate EIAH. Two sets of experiments, placebo (saline) and antihistaminic (tripelennamine HCl at 1.10 mg/kg iv, 15 min preexercise) studies, were carried out on seven healthy, exercise-trained Thoroughbred horses in random order 7 days apart. A...
McDonough P, Kindig CA, Erickson HH, Poole DC.The exercising Thoroughbred horse (TB) is capable of exceptional cardiopulmonary performance. However, because the ventilatory equivalent for O2 (VE/VO2) does not increase above the gas exchange threshold (Tge), hypercapnia and hypoxemia accompany intense exercise in the TB compared with humans, in whom VE/VO2 increases during supra-Tge work, which both removes the CO2 produced by the HCO buffering of lactic acid and prevents arterial partial pressure of CO2 (PaCO2) from rising. We used breath-by-breath techniques to analyze the relationship between CO2 output (VCO2) and VO2 [V-slope lactate t...
Van Harreveld PD, Lillich JD, Kawcak CE, Gaughan EM, Mclaughlin RM, Debowes RM.To evaluate clinical effects of immobilization followed by remobilization and exercise on the metacarpophalangeal joint (MPJ) in horses. Methods: 5 healthy horses. Methods: After lameness, radiographic, and force plate examinations to determine musculoskeletal health, 1 forelimb of each horse was immobilized in a fiberglass cast for 7 weeks, followed by cast removal and increasing amounts of exercise, beginning with hand-walking and ending with treadmill exercise. Lameness examination, arthrocentesis of both MPJ, single-emulsion radiographic examination, nuclear scintigraphic examination, grou...
Couroucé A, Chrétien M, Valette JP.We hypothesised that the derived physiological variables V2 and V4 (velocity to achieve a blood lactate concentration of 2 and 4 mmol/l, respectively), HR2 and HR4 (the corresponding heart rate) and V200 (the velocity for a heart rate of 200 beats/min) would improve with training state and age, in French Trotters. A total of 194 French Trotters from one training establishment were followed for 6 years and 1105 standardised field exercise tests performed on a sand training track. The horses were divided into 6 age groups (from 1 to > or = 6 years) and 4 training groups (beginning, endurance tra...
Bayly WM, Duvivier DH, Votion D, Vandenput S, Art T, Lekeux P.Six Warmblood horses suffering an acute exacerbation of COPD were tested to investigate whether inhalation of ipratropium bromide (IB) dry powder (2,400 microg) 30 min preexercise would improve their exercise capacity. A cross-over protocol with an inert powder placebo (P) was used. Mechanics of breathing and arterial blood gases were determined before treatment, after treatment but pre-exercise, and during an incremental exercise test. Oxygen consumption (VO2) was also measured before and during exercise, and the time to fatigue recorded. Inhalation of IB reduced total pulmonary resistance (R...
Hinchcliff KW, Lauderdale MA, Dutson J, Geor RJ, Lacombe VA, Taylor LE.High intensity exercise is associated with production of energy by both aerobic and anaerobic metabolism. Conditioning by repeated exercise increases the maximal rate of aerobic metabolism, aerobic capacity, of horses, but whether the maximal amount of energy provided by anaerobic metabolism, anaerobic capacity, can be increased by conditioning of horses is unknown. We, therefore, examined the effects of 10 weeks of regular (4-5 days/week) high intensity (92+/-3 % VO2max) exercise on accumulated oxygen deficit of 8 Standardbred horses that had been confined to box stalls for 12 weeks. Exercise...
Popot MA, Bobin S, Bonnaire Y, Delahaut PH, Closset J.Insulin-like growth factor-I (IGF -I) is likely to be an indicator of somatotropin (ST) administration in the horse. To investigate the different ways ST administration may be detected, the following aspects of IGF -I concentrations in plasma were studied: (i) the daily variation; (ii) variation following a treadmill test; (iii) concentrations at rest and after exercise; and (iv) concentrations in plasma from two young horses and two adults treated with methionyl equine somatotropin (e ST). In the population of horses at rest, IGF -I mean concentration (SEM) was 261 (104) ng ml(-1). In post ra...
Alexander RM.This research presents the hypothesis and findings that short muscle fibers in horses and other large mammals may protect bones and tendons from damaging vibrations during running, negating the previous […]
Murray RC, Vedi S, Birch HL, Lakhani KH, Goodship AE.It was hypothesised that subchondral bone thickness, hardness and remodelling are influenced by exercise intensity, and by location within a joint. Dorsal carpal osteochondral injury is a major cause of lameness in horses undergoing high intensity training. This project aimed to determine the subchondral bone thickness, formation, resorption and hardness at sites with high and low incidence of pathology in 2 year-old horses undergoing 19 weeks high intensity treadmill training or low intensity exercise, and to compare these factors between exercise groups. Dorsal and palmar test sites were ide...
Wilson AM, McGuigan MP, Su A, van Den Bogert AJ.The muscular work of galloping in horses is halved by storing and returning elastic strain energy in spring-like muscle-tendon units.These make the legs act like a child's pogo stick that is tuned to stretch and recoil at 2.5 strides per second. This mechanism is optimized by unique musculoskeletal adaptations: the digital flexor muscles have extremely short fibres and significant passive properties, whereas the tendons are very long and span several joints. Length change occurs by a stretching of the spring-like digital flexor tendons rather than through energetically expensive length changes...
Gellman KS, Bertram JE, Hermanson JW.The semispinalis capitis and splenius muscles of the horse were analyzed for gross morphology, microarchitecture, fiber length, and fiber type. Although these two muscles are similar in size and anatomical position, they are very different from one another in structural design and histochemistry, implying diverse functional roles in the animal's behavior. The histochemical staining profile was limited to two fiber types: slow oxidative and fast glycolytic. The splenius muscle has simple architecture, long fibers, and a 60/40 ratio of SO to FG cross-sectional area. The semispinalis capitis has ...
Jose-Cunilleras E, Hinchcliff KW, Sams RA, Devor ST, Linderman JK.In a randomized, balanced, crossover study each of six fit, adult horses ran on a treadmill at 50% of maximal rate of oxygen consumption for 60 min after being denied access to food for 18 h and then 1) fed corn (51.4 kJ/kg digestible energy), or 2) fed an isocaloric amount of alfalfa 2-3 h before exercise, or 3) not fed before exercise. Feeding corn, compared with fasting, resulted in higher plasma glucose and serum insulin and lower serum nonesterified fatty acid concentrations before exercise (P < 0.05) and in lower plasma glucose, serum glycerol, and serum nonesterified fatty acid conce...
Zips S, Peham C, Scheidl M, Licka T, Girtler D.The toelt of the Icelandic horse is a symmetric 4-beat gait, with alternating single and double support phases. By definition, the duration of the diagonal and ipsilateral stance phases should be similar. The aim of this study was to investigate the stride characteristics of horses ridden at toelt, and to compare these to previous descriptions of this gait. The kinematics of 23 Icelandic horses was measured using the Expert Vision System. Mature and sound horses, used for pleasure riding and/or competitions, were ridden at toelt at 3 different speeds. For each horse, 10 strides were measured a...
Preedy DF, Colborne GR.Metabolic and mechanical energy costs of locomotion can be combined to calculate locomotor efficiency, which is the quotient of the mechanical energy and metabolic costs. The purpose of this pilot study was to evaluate the mechanical and metabolic energy costs of locomotion at a range of 7 trotting speeds (2.5 to 6.2 m/s) on a level treadmill. A single, sound Thoroughbred horse was modelled as a system of 15 linked segments incorporating all 4 limbs, head, neck and trunk. The horse performed a continuous incremental exercise test at increasing trotting speeds while VO2 was recorded using a bre...
Roepstorff L, Johnston C, Drevemo S.The objective of this study was to validate a simple method to measure the mediolateral expansion of the heels and to apply this method in an in vivo experiment. It was also the aim to quantify the mediolateral expansion in different areas of the heel using an in vitro model. In the in vitro study, 5 right and 5 left distal forelimb specimens from 5 Standardbreds were mounted vertically in a custom-made compressive test machine. The heel expansion was measured using optical kinematic analysis and a potentiometer system. Specimens were tested unshod, with frog pressure and with the weightbearin...
Barrey E, Evans SE, Evans DL, Curtis RA, Quinton R, Rose RJ.The potential racing and locomotory profile of a Thoroughbred yearling should be taken into account for its training programme and racing career. A gait test has been designed to assist the trainer in this task. The aim of this study was to investigate the temporal and kinetic locomotory variables of Thoroughbreds at the gallop, in relationship to their racing ability. Thirty Thoroughbred horses in race training were tested at maximal speed during a training session. The training exercise consisted of a warming-up session at trot and canter for 10 min followed by a gallop session at increasing...
Holcombe SJ, Cornelisse CJ, Berney C, Robinson NE.To determine whether the hyoepiglotticus muscle has respiratory-related electromyographic activity and whether electrical stimulation of this muscle changes the position and conformation of the epiglottis, thereby altering dimensions of the aditus laryngis. Methods: 6 Standardbred horses. Methods: Horses were anesthetized, and a bipolar fine-wire electrode was placed in the hyoepiglotticus muscle of each horse. Endoscopic images of the nasopharynx and larynx were recorded during electrical stimulation of the hyoepiglotticus muscle in standing, unsedated horses. Dorsoventral length and area of ...
La Gerche A, Daffy JR, Mooney DJ, Forbes G, Davie AJ.It has been observed that microbubbles may pass through the pulmonary circulation of dogs and humans during exercise. In humans, this phenomenon has been associated with lower pulmonary artery pressures, enhanced right ventricular function and greater exercise capacity. In the exercising Thoroughbred horse, extraordinarily high cardiac outputs exert significant pulmonary vascular stresses. The aim of this study was to determine, using contrast echocardiography, whether Thoroughbred horses performing strenuous exercise developed pulmonary transit of agitated contrast microbubbles (PTAC). At res...
Doherty O, Booth M, Waran N, Salthouse C, Cí·¯ord D.The energy expenditure and heart rate of five Shetland ponies were measured during transport and compared with the values recorded while they were at rest and walking. Secondary aims of the study were to investigate whether there was any correlation between heart rate and energy expenditure and whether different orientations affected the values to different degrees. The measurements were recorded at one-minute intervals while the ponies were at rest, walking and being transported in four different orientations, on journeys lasting 30 minutes. There were significant increases (P < 0.001) in ...
Hall MC, Steel JD, Stewart GA.Data on resting heart rates, pre-exercise heart rates, the anticipatory rises before exercise, the influence of speed of work and recovery heart rates have been presented. Some observations on differences in the heart rate response on slow and fast working days are also recorded. In conformity with other workers, a linear relationship between heart rate and working speed within the range of 400-800 metre/min was observed. When the speed of work was between 400-800 metre/min, horses with resting ECG's classed as abnormal had significantly higher heart rates than those regarded as normal. It was...
Bayly WM, Kingston JK, Brown JA, Keegan RD, Greene SA, Sides RH.Horses experience major perturbations in acid-base balance during supramaximal exercise. Ion movement in and out of erythrocytes (RBCs) is believed to be important in maintaining acid-base balance but it is unclear as to the extent to which this happens, nor how it affects single measurements of ion concentrations in arterial and venous blood. Objective: To clarify the role RBCs play in mitigating perturbations in acid-base balance during high speed exercise in horses, and to describe associated differences in arterial (a) and mixed venous (v) concentrations of key ions. Methods: Six exercise-...
Mercier Q, Aftalion A.The objective of this work is to provide a mathematical analysis on how a Thoroughbred horse should regulate its speed over the course of a race to optimize performance. Because Thoroughbred horses are not capable of running the whole race at top speed, determining what pace to set and when to unleash the burst of speed is essential. Our model relies on mechanics, energetics (both aerobic and anaerobic) and motor control. It is a system of coupled ordinary differential equations on the velocity, the propulsive force and the anaerobic energy, that leads to an optimal control problem that we sol...
Foster CV, Harris RC.There was no detectable loss of total carnitine associated with intense exercise from the middle gluteal muscle of Thoroughbred horses. Measurements made on a single biopsy obtained during the course of a normal training and exercise programme may, therefore, be considered representative of the normal content at rest. The variability in total carnitine content within the normal muscle biopsy area amounted to 13.2 per cent of the normal mean content. Approximately 50 per cent of this variability could be attributed to covariation with citrate synthase, to which it was highly significantly corre...
Manohar M.Strenuously exercising Thoroughbreds exhibit a dramatic increase in pulmonary capillary blood pressure, which contributes to stress failure of pulmonary capillaries resulting in exercise induced pulmonary haemorrhage (EIPH). One strategy to prevent EIPH is, therefore, to lower the pulmonary capillary blood pressure of exercising horses. Recent work in several species suggests that nitric oxide plays a significant role in maintaining low vascular resistance in the pulmonary circulation; however, the effects of nitrovasodilators (which work via the same mechanism as nitric oxide) on equine pulmo...
Kriz NG, Hodgson DR, Rose RJ.To investigate the effects of deconditioning on cardiac dimensions and indices of cardiac function in horses. Methods: Thirteen 3-to 4-year-old Standardbred geldings. Methods: All horses had echocardiographic measurements performed at the conclusion of 9 months of intense training and at weeks 1.5, 4, 8, and 12 of deconditioning. Direct echocardiographic measurements included interventricular septal thickness, left ventricular internal dimensions, left ventricular freewall thickness, left atrial dimension, aortic diameter, diameter of the pulmonary artery, slopes of the mitral valve, heart rat...
Sosa León LA.One of the most common consequences of prolonged exercise is fluid and electrolyte depletion. Fluid and electrolyte losses during exercise may limit the horse's performance and, in extreme cases, jeopardize its health. To avoid or treat the deleterious effects of dehydration, fluid and electrolyte supplementation is essential. This article provides recommendations for fluid and electrolyte supplementation for horses involved in endurance-related events.
Fielding CL, Magdesian KG, Elliott DA, Cowgill LD, Carlson GP.To evaluate the use of multifrequency bioelectrical impedance analysis (MF-BIA) for estimating total body water (TBW), extracellular fluid volume (ECFV), and intracellular fluid volume (ICFV) in horses. Methods: 9 healthy mares. Methods: TBW and ECFV were measured by use of deuterium oxide and sodium bromide dilution techniques, respectively. Intracellular fluid volume was calculated as the difference between TBW and ECFV. Concurrently, MF-BIA recordings were obtained by use of 4 anatomic electrode positions and 3 measurements of length. Models for MF-BIA data were created for all combinations...
Arfuso F, Piccione G, Trimarchi F, Panzera MF, Giannetto C.Horse trekking is a non-competitive sport that, as other kinds of exercise, involves skeletal muscle effort and may implicate significant energy expenditure leading to stress. The aim of the current study was to assess the effect of trekking on metabolic and stress response as well as muscle damage markers in clinically healthy horses. Thirty horses were equally divided in 3 groups according to trekking course: Group A (trekking course 15 km long), Group B (trekking course 35 km long starting;), Group C (three trekking courses for three consecutive days; during the first day the trekking cours...
Winkelmayr B, Peham C, Frühwirth B, Licka T, Scheidl M.Force transmission under an English saddle (ES) at walk, trot and canter is commonly evaluated, but the influence of a side saddle (SS) on the equine back has not been documented. Objective: Force transmission under a SS, with its asymmetric construction, is different from an ES in walk, trot and canter, expressed in maximum overall force (MOF), force in the quarters of the saddle mat, and centre of pressure (COP). The biomechanics of the equine back are different under a SS compared to ES. Methods: Thirteen horses without clinical signs of back pain ridden in an indoor riding school with both...
Carlson GP, Jones JH.This study was undertaken to evaluate the effects of frusemide on the concentration of plasma electrolytes and the relationship between changes in electrolyte concentration and the simultaneous changes in acid-base balance in arterial and venous blood during intense exercise. Five exercise-conditioned Thoroughbred horses were exercised on a high-speed treadmill at a slope of 10% at speeds known to exceed VO2max. Horses participated in 3 randomised exercise trials in which they received either placebo (control), low-dose frusemide (0.5 mg/kg bwt), or high-dose frusemide (1.0 mg/kg) 4 h prior to...
Rej R, Rudofsky U, Magro A, Prendergast J.Aminotransferase activities were measured in the serum of two- to three-year-old Thoroughbred fillies and colts during a four week period of peak training for flat racing. Aspartate aminotransferase (AspAT, EC 2.6.1.1), mitochondrial aspartate aminotransferase (m-AspAT) and alanine aminotransferase (AlaAT, EC 2.6.1.2) activities in serum were measured and the relative proportions of apoenzyme and holoenzyme were determined. The aminotransferase activities were increased only slightly immediately following exercise. This small and immediate post exercise increase in activity did not vary greatl...
Karagianni AE, Summers KM, Couroucé A, Depecker M, McGorum BC, Hume DA, Pirie RS.Mild-to-moderate equine asthma is prevalent in young racehorses, particularly early in their training period. Although the precise etiopathogenesis remains undetermined, it is possible that the susceptibility of this population might partly reflect an exercise-associated immune derangement at the level of the airway. We performed a genome-wide basal gene expression scan on alveolar macrophages (AMs) isolated from Standardbred racehorses before and after commencement of competition race training with a view to identifying any exercise-associated gene expression modulation consistent with functi...
Zawadzkas XA, Sides RH, Bayly WM.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 p...
Fredricson I, Drevemo S, Dalin G, Hjertën G, Björne K.Locomotive disorders constitute a serious problem in horse racing which will only be rectified by a better understanding of the causative factors associated with disturbances of gait. This study describes a system for the quantitative analysis of the locomotion of horses at speed. The method is based on high-speed cinematography with a semi-automatic system of analysis of the films. The recordings are made with a 16 mm high-speed camera run at 500 frames per second (fps) and the films are analysed by special film-reading equipment and a mini-computer. The time and linear gait variables are pre...
Chen J, Gollnick PD.Horses were subjected to treadmill running at 65% (submaximal) or 100% (maximal) VO2,max to examine the effects of exercise on subcellular distribution of hexokinase (HK) and on mitochondrial respiration. It is hypothesized that the fraction of HK bound to mitochondria will be reduced due to an elevation of glucose-6-phosphate (G-6-P) concentration in the exercising muscle and that such release of HK from mitochondria will depress oxidative phosphorylation. Changes in muscle G-6-P concentration, pH, subcellular HK distribution, mitochondrial respiration and other metabolites were determined in...
Ainsworth DM, Smith CA, Eicker SW, Ducharme NG, Henderson KS, Snedden K, Dempsey JA.In exercising quadrupeds, limb movement is often coupled with breathing frequency. This finding has lead some investigators to conclude that locomotory forces, associated with foot plant, abdominal visceral displacements or lumbo-sacral flexion, are the primary determinants of airflow generation. Analysis of respiratory muscle electrical activation (EMG) and contraction profiles in chronically instrumented dogs and horses, along with measurements of esophageal pressure (Pes) changes and limb movements, provide evidence that each breath during the exercise hyperpnea is determined by respiratory...
Gansen S, Lindner A, Marx S, Mosen H, Sallmann HP.The effects of 3 different conditioning programmes on muscle glycogen concentration in horses were examined. Speed of exercise was selected according to the blood lactate values for each horse derived from a standardised exercise test before beginning a conditioning programme. Six 2-year-old Haflinger stallions were assigned randomly to one of 3 conditioning programmes according to a 6 x 3 latin square design: 45 min at their individual v1.5 or v2.5 and 25 min at v4. Each conditioning programme lasted 6 weeks (21 exercise sessions), followed by 5 weeks without conditioning (resting period). Al...
Murphy J.This study investigated the effects of weighted boots on horses (n=6) jumping a 1.25 m oxer fence. The horses had similar training experience and were assigned to two groups of three subjects (groups G1 and G2). All horses performed 10 jumping efforts: G1 horses made attempts 1-5 without boots and 6-10 with boots; G2 made attempts 1-5 with boots and 6-10 without boots. Data were available via sagittal plane S-VHS recordings and t test analyses focussed on limb-placement dimensions. There were no differences among performances of the horses in the horizontal plane, but there were significant di...
Manohar M, Goetz TE, Hassan AS.Because sensitivity of equine pulmonary vasculature to endogenous as well as exogenous nitric oxide (NO) has been demonstrated, we examined whether endogenous NO production plays a role in exercise-induced arterial hypoxemia. We hypothesized that inhibition of NO synthase may alter the distribution of ventilation-perfusion mismatching, which may affect the exercise-induced arterial hypoxemia. Arterial blood-gas variables were examined in seven healthy, sound Thoroughbred horses at rest and during incremental exercise protocol leading to galloping at maximal heart rate without (control; placebo...
Räsänen LA, Myllymäki T, Hyyppä S, Maisi P, Pösö AR.Plasma concentrations of hypoxanthine, uric acid, and allantoin, which are breakdown products of adenine nucleotides, were measured in Standardbred and Finnhorse trotters during and after an exercise test on a high-speed treadmill, after an incremental exercise test performed on a racetrack, and after a racing competition. Fiber-type composition of the middle gluteal muscle and the muscle concentrations of adenine nucleotides and inosine monophosphate were measured after the racetrack test. Changes in the concentration of hypoxanthine were not observed in any of the tests. Peak concentration o...
Schryver HF, Hintz HF, Lowe JE.The effect of exercise on the pathways of metabolism of 40Ca and 47Ca was studied in 4 yearling Standardbred horses in 4 consecutive treatment periods: (1) no exercise, (2) trotting 16 km/day, (3) trotting 10 km/day, and (4) no exercise. Metabolic balance studies and studies of 47Ca kinetics were conducted during the final week of each month-long treatment period. The urinary excretion of 40Ca and 47Ca decreased 50% to 75% during the exercise periods. Retention of 47Ca increased during the exercise periods, but the retention of dietary Ca (40Ca) did not change. The efficiency of Ca absorption ...
