Exercise in horses encompasses the physical activities that horses engage in, either through natural behaviors or structured training programs. These activities impact a horse's musculoskeletal, cardiovascular, and respiratory systems, influencing overall health and performance. Exercise can vary in intensity, duration, and frequency, and its effects are studied to understand conditioning, endurance, and recovery processes in equines. Research in this field often focuses on the physiological adaptations to different types of exercise, the prevention of exercise-related injuries, and the optimization of training regimens for various equestrian disciplines. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, biomechanical, and health-related aspects of exercise in horses.
Weiss DJ, Geor RJ, Burger K.To determine whether furosemide treatment altered the blood flow properties and serum and RBC electrolyte concentrations of Thoroughbreds during submaximal treadmill exercise. Methods: Thoroughbreds were subjected to submaximal treadmill exercise with and without treatment with furosemide (1 mg/kg of body weight, IV). Methods: 5 healthy Throughbreds that had raced within the past year and had no history of exercise-induced pulmonary hemorrhage. Methods: Venous blood samples were obtained before exercise, at treadmill speeds of 9 and 13 m/s, and 10 minutes after exercise, and hemorheologic and ...
Sinha AK, Gleed RD, Hakim TS, Dobson A, Shannon KJ.The object of this study was to relate pulmonary capillary pressure to arterial and wedge pressures during exercise. Pulmonary vascular pressures were measured in six standardbred horses exercising at speeds equivalent to 75, 90, and 100% of maximal heart rate. Vascular pressures were measured with transducer-tip catheters and expressed relative to esophageal pressure. Pulmonary capillary pressure was estimated by the arterial-occlusion technique modified for exercise. Mean pulmonary arterial, capillary and wedge pressures increased from 30.5 +/- 6.3, 17.8 +/- 4.3, and 13.4 +/- 1.6 mmHg, respe...
Ray CS, Baxter GM, McILWRAITH CW, Trotter GW, Powers BE, Park RD, Steyn PF.The objective of this study was to determine if damage to the articular cartilage alone or articular cartilage plus subchondral bone of the distal medial femoral condyle of young, exercised horses resulted in the formation of subchondral cystic lesions. Twelve Quarter Horses (age 1-2 years), free of clinical and radiographic signs of osteochondrosis and lameness were used. In 6 horses (Group 1), a 15 times 1 mm linear full thickness defect in the articular cartilage was made arthroscopically on the weightbearing surface of the distal aspect of the medial femoral condyle. In the other 6 horses ...
The Journal of physiologyApril 15, 1996
Volume 492 ( Pt 2), Issue Pt 2 587-596 doi: 10.1113/jphysiol.1996.sp021331
Lafortuna CL, Reinach E, Saibene F.1. To investigate the effect of locomotor activity on the pattern of breathing in quadrupeds, ventilatory response was studied in four healthy horses during horizontal and inclined (7%) treadmill exercise at different velocities (1.4-6.9 m s(-1)) and during chemical stimulation with a rebreathing method. Stride frequency (f(s)) and locomotor-respiratory coupling (LRC) were also simultaneously determined by means of video recordings synchronized with respiratory events. 2. Tidal volume (V(T)) was positively correlated with pulmonary ventilation (V(E)) but significantly different linear regressi...
Raulo SM, Hyyppa S, Räsänen LA, Pösö AR.The activities of lysosomal enzymes, such as beta-glucuronidase and N-acetyl-beta-D-glucosaminidase, have been shown to increase in muscle after endurance exercise. We examined whether measurable activities of lysosomal enzymes are present in equine plasma and whether the exercise-induced changes in the muscle are reflected in plasma. Six trained Standardbred trotters performed three exercise bouts with 1 h intervals and the same procedure was repeated 3 days later. Venous blood samples and muscle biopsies from the middle gluteal muscle were taken before and after exercise. The activities of b...
Persson SG, Funkquist P, Nyman G.The purposes of this study were to elucidate the influences of age and sex on the mass specific blood volume parameters: total blood volume (TBV/BW, ml/kg), plasma volume (PV/ BW, ml/kg), total red cell volume (CV/BW, ml/kg) and maximal packed cell volume (PCV, l/l, i.e. after total mobilisation of the splenic red cell reservoir) and to establish reference values for these in normally performing Standardbred trotting race horses. In total 205 horses were studied. They were all, according to their owners and/or trainers, performing satisfactorily in racing or training for shortly impending raci...
Theoret CL, Barber SM, Moyana T, Townsend HG, Archer JF.The reparative ability of equine synovium was determined by gross, histological, and ultrastructural examination. The functional potential of the synovium was estimated by examination of synovial cell organelles with transmission electron microscopy. Results from rested and exercised horses were compared to determine the effect of exercise on synovial healing. The response of synovectomized joint to exercise was evaluated with a standardized lameness examination and by gross, histological, and histochemical observations of the articular cartilage. A 7-mm diameter motorized synovial resector wa...
Tyler CM, Hodgson DR, Rose RJ.The VO2(max) in racehorses is approximately double that of elite human athletes and the rate of increase in VO2 at the onset of high intensity exercise is much greater than in man. The kinetics of gas exchange are affected by a warm-up prior to exercise in humans, there being a greater aerobic contribution to high intensity exercise after warm-up. Our hypothesis was that a warm-up would increase aerobic energy delivery in racehorses during high intensity exercise. Thirteen fit Standardbred racehorses ran to fatigue at 115% of VO2(max) on a treadmill at 10% slope. Prior to acceleration, horses ...
Weiss DJ, Richwagen K, Evanson OA.To evaluate the contribution of hematocrit and RBC deformability to pulmonary vascular pressures of racehorses. Methods: Pony lungs were isolated and right and left lungs were perfused separately with blood. The effects of changing hematocrit and of pentoxifylline treatment were evaluated. Methods: 11 healthy mixed-breed ponies. Methods: Ponies were anesthesized, blood was collected, and lungs were removed and perfused with blood at constant flow rate. Results: Increasing the hematocrit from 35% to 65% resulted in increases in pulmonary arterial pressure (53%, 45%), capillary shear stress (45%...
Holcombe SJ, Beard WL, Hinchcliff KW.To investigate the effect of a mask and pneumotachograph on ventilation, respiratory frequency, and tracheal and nasopharyngeal pressures in horses running on a treadmill. Methods: Six horses ran at 50, 75, and 100% of the speed that resulted in maximum oxygen consumption, with and without a mask and pneumotachograph. Tracheal and pharyngeal inspiratory and expiratory pressures, respiratory frequency, and arterial blood gases were measured. Methods: Six Standardbred horses. Methods: Oxygen consumption was measured during an incremental exercise test to determine the speed that resulted in maxi...
Kuwabara M, Inukai N, Inanami O, Miyake YI, Tsunoda N, Maki Y, Sato F.Hotbred (Thoroughbred) horses were grouped into three classes according to the levels of constant physical exercise (foals, 6 months old; racing horses, 5 years old; horses for breeding, 6-10 years old), and lipid peroxide levels in their sera were measured as thiobarbituric acid-reactive substances. No significant differences were observed among them. The superoxide-scavenging abilities of sera were measured next; to examine the antioxidative properties of hotbreds, and were found to be highest in the racing horses. The higher scavenging ability of the racing horses might contribute to keep t...
Hiney KM, Potter GD.Although a lot of research has been directed at attempts to improve performance of the equine athlete, many of the studies reviewed herein did not show statistically significant improvements in race times or increased time to fatigue. However, it must be remembered that success in racing performances is not always measured in time, but by comparative lengths or even by a nose. Therefore, improvement in the ability of an individual equine athlete is not always measurable and success is most frequently determined by one animal being better than the others in a particular competition. Therefore, ...
McLaughlin RM, Gaughan EM, Roush JK, Skaggs CL.The objective of the study reported here was to evaluate the effects of changing velocity on stance time and ground reaction force (GRF) measurements in horses at the walk and trot. Methods: Force plate gait analysis was used to evaluate clinically normal horses at variable velocities. Ground reaction force measurements and stance times were recorded and compared. Methods: 12 adult horses. Methods: Data were obtained from 192 valid trials at the walk and 162 valid trials at the trot. Vertical, braking, and propulsive peak forces and impulses were measured. Pearson's correlation coefficients we...
Mills PC, Smith NC, Casas I, Harris P, Harris RC, Marlin DJ.The effects of prolonged variable-intensity and short-term high-intensity exercise on indices of oxidative stress and iron homeostasis were compared in six fit horses under cool [20 degrees C, 40% relative humidity (RH)] or hot/humid (30 degrees C, 80% RH) environmental conditions. The exercise protocols were designed to simulate equine competition, including racing (intense exercise) or the speed and endurance phase of a 3-day event (prolonged exercise). Increased plasma concentrations of lipid hydroperoxides and haemolysate concentrations of oxidised glutathione (GSSG) were measured within 3...
Desmecht D, Linden A, Amory H, Art T, Lekeux P.Fifty-eight healthy horses were studied during five sporting events of various intensities and durations, namely show-jumping (n = 6), cross-country in a three-day event (n = 30), trotting races (n = 7), galloping races (n = 7) and endurance rides (n = 8). Venous blood samples were collected at rest and immediately after exercise and analysed for plasma cortisol (CORT) and lactate (LA) levels. The experimental procedure was the same throughout the investigation so as to permit a reliable comparison between the five types of exercise. The type of event significantly affected both the resting (p...
Moore BR, Krakowka S, Cummins JM, Robertson JT.Natural human interferon-alpha (nHuIFN alpha) was administered to actively training Standardbred racehorses with inflammatory airway disease (IAD). Inflammatory airway disease was characterized by poor exercise performance and inflammation and exudate in the upper and lower airway. Placebo, 50, 150, or 450 units(U) of nHuIFN alpha was administered orally for 5 consecutive days to eight horses per treatment group in a double-blind, randomized block design. Response to nHuIFN alpha was monitored by semiquantitative endoscopic examination score and cytologic examination of bronchoalveolar lavage ...
Davankar SP, Deane NJ, Davies AS, Firth EC, Hodge H, Parry DA.Since horses bred for the racing industry are subject to rigorous training procedures there is a real need to understand how the stresses experienced by their tendons and ligaments in vivo relate to the major load-bearing elements-the collagen fibrils. Consequently, an age-related study has been made of the collagen fibril diameter distributions of nine ligaments in and around the equine carpus. This is the first stage of a larger study aimed at understanding the ultrastructural changes that occur as a result of exercise. Most of the ligaments showed a bimodal diameter distribution at maturity...
Buchner HH, Savelberg HH, Schamhardt HC, Barneveld A.The kinematic patterns of head and trunk were studied in horses during induced supporting limb lameness to understand the mechanisms horses use to compensate for lameness and to evaluate different symmetry indices for their significance as lameness indicators. Using the locomotion analysis system CODA-3 the kinematics of 11 clinically nonlame Dutch Warmblood horses were recorded while walking (1.6 m/s) and trotting (3.5 m/s) on a treadmill. A transient lameness model, evoking pressure induced pain on the hoof sole, was used to induce 3 degrees of fore- and hindlimb lameness. Peak vertical disp...
Lund RJ, Guthrie AJ.This study determined the maximal O2 uptake (VO2max) of Thoroughbred horses acclimatised to mild hypobaric conditions using a standard exercise test on a treadmill inclined at a 7% slope. The O2 uptake (VO2) versus speed relationship was linear below the exercise intensity required to attain VO2max. The VO2max of individual horses ranged from 143.5 to 172.6 ml/kg/min. The proportion of total variance for the VO2 versus speed relationship was greater than 0.992, and the coefficients of variation in repeated tests in individual horses ranged between 0.07 and 1.54%. The VO2 versus speed relations...
Escribano BM, Castejon FM, Santisteban R, Aguera EI, Rubio MD.A study has been made of the variations experienced by the hemogram and blood volume indices in 16 Andalusian horses after carrying out an exercise test of increasing intensity consisting of 3 sequences of 1000 m each, before and after being subjected to a daily exercise programme for two months. Samples were taken by external jugular vein puncture: while at rest, within the first minute of finalizing each exercise stage and at 10 and 15 minutes of recovery. Both the red blood cells and the hematocrit value showed a significant decrease in their mean values after two months training; conversel...
Palmer JL, Bertone AL, Malemud CJ, Carter BG, Papay RS, Mansour J.The relevance of site and the influence of exercise on third carpal articular cartilage proteoglycan (PG) were assessed in 16 horses. Six horses were exercised (exercised group) for 30 minutes, 3 times/wk, for 6 weeks. The other 10 horses (nonexercised group) were housed in box stalls for the same 6-week period. At week 6, articular cartilage from the proximal surface of the right third carpal bone was harvested and cultured with radioactive sulfate to label newly synthesized PG. Endogenous PG was measured by use of a uronic acid assay. Newly synthesized and endogenous PG were characterized by...
Sticker LS, Thompson DL, Bunting LD, Fernandez JM, DePew CL, Nadal MR.Twelve light horse mares were fed a control diet that provided 100% of their maintenance protein and energy requirements for 7 d and were then either continued on the control diet or totally deprived of feed (with access to water) for 3 d . Plasma samples were drawn twice daily throughout the experiment, at 15-min intervals for 9 h beginning 45 h after feed removal, and at 10-min intervals around an exercise bout beginning 73 h after feed removal. Feed deprivation increased (P < or = .06) whole blood beta-hydroxybutyrate and plasma NEFA, urea N, L-lactate, and glucagon concentrations, decrease...
McConaghy FF, Hales JR, Rose RJ, Hodgson DR.Five horses were exercised on a treadmill [to central blood temperature (Tcore) approximately 42.5 degrees C]. Three of those horses were heated at rest in a climate room (53 degrees C, 90% relative humidity) (to Tcore approximately 41.5 degrees C). Temperatures were measured in the rectum, hypothalamus (Thyp), cerebrum, and cavernous sinus (Tsinus), on the skin of the head and midside, and Tcore. When Tcore increased above 38.5 degrees C, Thyp remained 0.6 +/- 0.1 degree C (SE) lower during heat exposure and 1 +/- 0.2 degrees C lower during exercise. During heat exposure, Tsinus was 2.2 +/- 0...
Jones JH, Carlson GP.The metabolic power required for sustained exercise in the horse is proportional to running speed. Moderately fast speeds require substantial energy expenditure and result in the generation of a massive metabolic heat load. Quantitative estimates of energy expenditure and heat production of horses at various running speeds were developed using empirically derived data from treadmill studies. Total metabolic power represents the sum of aerobic power indicated by the rate of oxygen consumption and net anaerobic power indicated by the rate of plasma lactate accumulation. These data were applied t...
Harris PA, Marlin DJ, Scott CM, Harris RC, Mills PC, Michell AR, Orme CE, Roberts CA, Schroter RC, Marr CM.Four horses (H, J, N and M) undertook a simulated competition exercise test (CET), designed to simulate physiological and metabolic stresses of the Speed and Endurance (S & E) test of a 3-day-event, under 3 different environmental conditions: 20 degrees C/40% relative humidity (RH) (cool, dry [CD] 2 sessions); 30 degrees C/40% RH (hot, dry [HD]) and 30 degrees C/80% RH (hot, humid [HH]) (Marlin et al. 1995a). Venous blood samples for electrolyte and total protein (TP) determinations were collected from indwelling catheters at predetermined time points throughout each CET and initial 30 min...
McCutcheon LJ, Geor RJ, Hare MJ, Ecker GL, Lindinger MI.The objective of this study was to determine the composition and extent of sweat losses during submaximal exercise under hot and humid conditions and to compare these findings with the same exercise protocol conducted under cool, dry and hot, dry conditions. Five Thoroughbred horses (age 3 to 6) completed exercise tests under each of 3 environmental conditions in random order: cool, dry (CD), room temperature (T) = 20 degrees C, relative humidity (RH) = 45-55%; hot, dry (HD), T = 32-34 degrees C, RH = 45-55%; and hot, humid (HH), T = 32-34 degrees C, RH = 80-85%. Horses exercised at 50% of the...
Andrews FM, Geiser DR, White SL, Williamson LH, Maykuth PL, Green EM.Haematological and biochemical changes in horses competing in the Endurance Test (Phase T and D) of an advanced Horse Trial (HT, n = 22) and the Endurance Test (Phases A-D) of an advanced (CCI) 3-day-event (TD, n = 11) over a similar course on the same day were studied. Environmental conditions during the event were cool (5.5-11.1 degrees C). Blood samples were collected from the horses in each group the evening prior to the Endurance Test, within 60 s after, and 10 min after, completion of Phase D (cross-country jumping). The following were determined in the blood samples and compared between...
Davies HM, Merritt JS.Bone strains quantify skeletal effects of specific exercise and hence assist in designing training programmes to avoid bone injury. Objective: To test whether compressive strains increase on the lateral surface of the inside third metacarpal bone (McIII) and the medial surface of the outside McIII in a turn. Methods: Rosette strain gauges on dorsal, medial and lateral surfaces of the midshaft of the left McIII in 2 Thoroughbred geldings were recorded simultaneously during turning at the walk on a bitumen surface. Results: Medial surface: Compression peaks were larger in the outside limb. Tensi...
Purohit RC, Nachreiner RF, Humburg JM, Norwood GL, Beckett SD.Circulating concentrations of angiotensin I and plasma renin activity (PRA) were determined in 45 Thoroughbreds before prerace medication (at rest), 1 to 1 1/2 hours before racing but after prerace medication (prerace), within 15 minutes after racing (immediately postrace), and between 1 to 2 hours after racing. Angiotensin I was measured by radioimmunoassay, and PRA was determined by the rate of generation of angiotensin I in plasma incubated at 37 C. Irrespective of prerace medication, there was a marked increase in angiotensin I (0.478 +/- 0.034 to 0.848 +/- 0.051 ng/ml) and PRA (0.191 +/- ...
Owen RA, Marsh JA, Hallett FR, Lumsden JH, Johnson J.Methylprednisolone acetate was injected repeatedly into both intercarpal joints of a horse that had a 3rd carpal bone fracture in 1 limb. Synovial fluid from intercarpal and radiocarpal joints of both limbs were obtained serially for study. Arthropathy developed in the fractured joint following prolonged corticosteroid therapy and exercise. In the corticosteroid-injected normal joint, the hyaluronic acid concentration initially decreased, then increased. A depletion in cartilage matrix was seen at necropsy, 175 days after onset of treatment. Determination of total protein content in synovial f...
Linden A, Art T, Amory H, Desmecht D, Lekeux P.Seven sport horses were investigated to compare physiological and pharmacological stresses on the plasma glucocorticosteroid levels. Venous blood was sampled and analysed for cortisol concentrations before and after each type of stress. The physiological stress was induced by the completion of a cross-country and the pharmacological one, by an intravenous ACTH administration (200 micrograms) in the same horses, one week after the course. Both exercise and ACTH injection induced a highly significant cortisol increase of 79 +/- 0.10% and 160 +/- 0.18%, respectively. The relative plasma cortisol ...
Parks CM, Manohar M.In recent years, increasing attention has been focused on the physiological responses of the horse to maximal exercise. Cardiovascular response in near maximally exercised galloping ponies (heart rate 225 +/- 7 beats/min; whole body oxygen consumption 122 +/- 12 ml/min/kg) comprised a marked increase in blood flow to the cerebellum, myocardium, diaphragm and the working muscles, while renal blood flow decreased precipitously. Cerebral and brainstem perfusion did not vary from resting values. Transmural homogeneity of myocardial blood flow persisted during near maximal exercise. It was reported...
Littlejohn A, Snow DH.These studies investigated circulatory, respiratory and metabolic responses in four Thoroughbred geldings during the first 400 metres of galloping (mean speed 14.4 +/- 0.38 m.s-1), cantering (mean speed 10.0 +/- 0.61 m.s-1) and walking (mean speed 1.58 +/- 0.05 m.s-1) from a standing start. A radio-controlled device which collected blood samples anaerobically during each 100 m section of the exercise track allowed analyses of changes in and functional relationships of the variables measured. During the 400 m gallop, the mean heart rate (HR) increased from 125 to 201 beats.min-1 and the haemato...
Smith JM, Meyers KM, Barbee DD, Schott H, Bayly WM.To determine whether plasma von Willebrand factor (vWf) concentration changes in horses during and after treadmill exercise. Methods: 5 mature, fit Thoroughbreds. Methods: A blood sampling catheter was placed in the right jugular vein. A warm-up period was followed by a 3-minute rest period. Horses were galloped at racing pace until fatigued (about 2 minutes). Blood samples were collected prior to warm-up, during the postwarm-up rest period, 1 minute into the run, at cessation of the run, and 5 to 120 minutes after cessation of the run. vWf activity was measured by ELISA and corrected for plas...
Borgia LA, Valberg SJ, McCue ME, Pagan JD, Roe CR.To evaluate effects of fats with odd and even numbers of carbon atoms on muscle metabolism in exercising horses with polysaccharide storage myopathy (PSSM). Methods: 8 horses with PSSM (6 females and 2 males; mean +/- SD age, 6.3 +/- 3.9 years). Methods: Isocaloric diets (grain, triheptanoin, corn oil, and high-fat, low-starch [HFLS] feed) were fed for 3 weeks each; horses performed daily treadmill exercise. Grain was fed to establish an exercise target, and HFLS feed was fed as a negative control diet. Daily plasma samples were obtained. For each diet, a 15-minute exercise test was performed,...
Urschel KL, McKenzie EC.Skeletal muscle comprises 40% to 55% of mature body weight in horses, and its mass is determined largely by rates of muscle protein synthesis. In order to support exercise, appropriate energy sources are essential: glucose can support both anaerobic and aerobic exercise, whereas fat can only be metabolized aerobically. Following exercise, ingestion of nonfiber carbohydrates and protein can aid muscle growth and recovery. Muscle glycogen replenishment is slow in horses, regardless of dietary interventions. Several heritable muscle disorders, including type 1 and 2 polysaccharide storage myopath...
McDonough P, Kindig CA, Hildreth TS, Behnke BJ, Erickson HH, Poole DC.Maximal cardiac performance is improved in man during upright compared to supine exercise. Whether cardiac performance in quadrupeds is dependent upon body position is unknown. Therefore, we undertook the present investigation to determine if peak cardiac output (Qpeak) would be influenced by body inclination in the Thoroughbred horse. To test the hypothesis, four Thoroughbred horses performed an incremental exercise protocol (speed increased by 1 m/s/min to fatigue) on both a level (L) and inclined (I: 6 degrees) treadmill. Specifically, we hypothesised that Qpeak would be increased on the in...
Peters LW, Smiet E, de Sain-van der Velden MG, van der Kolk JH.In particular branched-chain amino acids might limit muscle protein loss in pathological conditions. Little is known on basic amino acid utilization of muscle in horses. Objective: To assess amino acid utilization by the hindlimb of horses at rest and following low intensity exercise. ANIMALS & METHODS: Amino acid uptake by the hindlimb was investigated using the arteriovenous difference technique. Blood from six warmblood mares (mean age 12 ± 3 (SD) years and weighing 538 ± 39 kg) was collected simultaneously from the (transverse) facial artery and from the caudal vena cava. Food was wi...
Vinardell T, David F, Galezowski AM, Ali M, Qasim M, Massie SL, McCrae P, Filho S, Leguillette R.Swimming is used for rehabilitation of musculoskeletal injuries and for conditioning to improve equine fitness. However, there are anecdotal reports that suggest that tethered swimming can induce epistaxis, likely secondary to exercise-induced pulmonary hemorrhage (EIPH). The objective of this observational, prospective study was to investigate if EIPH occurs during intensive free-swimming training sessions (5 × 70m) using 15 endurance horses. On tracheo-bronchoscopic evaluations following swimming, low grade mucus scores were observed, but no tracheal blood was observed. Bronchoalveolar la...
Siewert C, Böttcher A, Hellige M, Beyerbach M, von Rautenfeld DB, Seifert H.This study tested for the first time an optoelectronic device (Perometer*) measuring limb volume of horses. An analysis of its application was performed regarding the influence of different types of physical exercise on the volume of the extremities. 40 horses were divided into four groups often horses, each group being exposed to exercise, differing in kind and duration of lunging, horse-ridden and riderless. The volume measurement was performed by determining the inactive value (I) after a twelfe-hour standing period, the load value (II) immediately after exercise and recovery value (III) on...
Hiraga A, Sugano S.The history of research on the exercise physiology of racehorses in Japan dates back to the 1930s. A research report entitled "Studies on exercise physiology and performance testing of the racehorse", published in 1933 by Shigeo Matsuba and Torao Shimamura of The University of Tokyo, was epoch-making and the most important study in the history of equine exercise physiology in Japan. Research results were reported from 92 Thoroughbred racehorses in a large-scale project during the period of 1928 to 1932 at the Shimofusa Imperial Farm and the Koiwai Farm, which were the two greatest racehorse fa...
Potard US, Leith DE, Fedde MR.Thoroughbred (TB) and draft horses (DH) have long been selected for tasks of very different intensities and force-speed relationships. To study their adaptations, we measured O2 consumption and related variables in three TB and four DH during progressive exercise tests on a level treadmill. The horses exerted a draft force of 0, 5, 10, 15, or 20% of their body weight at speeds that increased by 2 m/s every 3 min until they could not maintain that speed. We found that TB could exert the same draft forces as DH and, at each force, TB achieved about twice the speed, twice the external power, and ...
Jansson A, Lindholm A, Dahlborn K.The effect of a temporary increase in plasma aldosterone concentration on Na(+), K(+), and water balance was investigated in four horses. Aldosterone was injected intravenously for 6 h at 20-min intervals (total 5.4 microg/kg body wt). Samples were taken for 24 h before, during, and for 48 h after the treatment. Aldosterone treatment reduced the Na(+) loss via urine and feces by 99 and 72%, respectively, later followed by a marked increase in Na(+) excretion by both pathways. During the first 6 h after the treatment, fecal K(+) excretion was elevated, and the plasma K(+) concentration was lowe...
Raulo SM, Hyyppa S, Räsänen LA, Pösö AR.The activities of lysosomal enzymes, such as beta-glucuronidase and N-acetyl-beta-D-glucosaminidase, have been shown to increase in muscle after endurance exercise. We examined whether measurable activities of lysosomal enzymes are present in equine plasma and whether the exercise-induced changes in the muscle are reflected in plasma. Six trained Standardbred trotters performed three exercise bouts with 1 h intervals and the same procedure was repeated 3 days later. Venous blood samples and muscle biopsies from the middle gluteal muscle were taken before and after exercise. The activities of b...
Garcia MC, Beech J.Two identical experiments, using Standardbred and Thoroughbred horses (experiment A, n = 31; experiment B, n = 17) on a swimming regimen, were performed 1 week apart to evaluate short-term heart rate, hematologic, and endocrinologic changes. Horses were placed in 4 categories based on duration of swimming (1 to 5, greater than 5 to 10, greater than 10 to 15, and greater than 15 minutes). Heart rate, PCV, and plasma concentrations of total protein, cortisol triiodothyronine, thyroxine, insulin, and glucose of each horse were evaluated before, immediately after, and 1 hour after swimming. For ex...
Kemmink A, Westermann CM, van der Kolk JH.The quantity of glucose disposal during exercise (walk and trot) compared to rest by use of the hyperglycaemic clamp technique has not been reported previously and has relevance to nutritional requirements. Objective: Exercise (walk and trot) significantly increases glucose disposal compared to rest. Methods: Seven healthy Dutch Warmblood mares, all in dioestrus, mean ± s.d. age 11.6 ± 2.4 years and weighing 569 ± 40 kg were fasted for 12 h prior to a hyperglycaemic clamp at rest (maintaining a steady state of the blood glucose concentration during 30 min), walk (10 min, 1.5 m/s), trot (20 ...
Buchalski FM, Rankins EM, Malinowski K, McKeever KH.The purpose of this study was to examine the effects of an external nasal strip on thermoregulation during submaximal exercise in Standardbred horses. While several studies have been conducted to determine the effects of the external nasal strip on airway resistance, exercise induced pulmonary hemorrhage, gas exchange, and time to fatigue in maximally exercising horses, the effects of the nasal strip on equine thermoregulation have not yet been examined. It was hypothesized that the application of an external nasal strip would alter central venous temperature (T), skin temperature (T), and exe...
Breuhaus BA.This study was performed to determine whether anhidrotic horses have altered thyroid function compared with horses that sweat normally. Objective: Anhidrotic horses have normal thyroid function. Methods: Ten client-owned horses with clinical signs of anhidrosis were paired with 10 horses living in the same environment that had normal sweat production. Methods: Horses were diagnosed as having normal sweat production or being anhidrotic based on responses to intradermal injections of terbutaline and physiologic responses to lunging exercise. Control horses were selected from the same environment...
Santosuosso E, David F, Massie S, Filho SA, McCrae P, Johnson S, Leguillette R.Cardiac arrhythmias have not been previously reported in horses while swimming. Objective: To describe the type and frequency of encountered arrhythmias during repetitive swimming cycles. Methods: Descriptive observational study. Methods: Sixteen horses swam five pool lengths (75 m), each separated by an active recovery walk. Continuous electrocardiograms (ECGs) were recorded (n = 80) and analysed during the pre-swim, swim and active-recovery periods. Arrhythmias were categorised as sinus arrhythmia (SA), sinus block, sinus pause (compensatory and non-compensatory), second degree atriovent...
Poškienė I, Gruodytė R, Autukaitė J, Juozaitienė V, Antanaitis R.Fédération Equestre Internationale (FEI) has described equine endurance racing as the second largest discipline in the world, above which is only show jumping. The Žemaitukai is an ancient indigenous Lithuanian horse breed known since the 6th or 7th century. The Arabian horse breed is one of the oldest human-developed horse breeds in the world. Compared with other race horse breeds, the muscle tissue of Arabian horses is characterized by significant differences in structure-a predominance of oxidative fiber type I is observed in Arabians, making them the prevailing breed in endurance racing...
Miller PA, Lawrence LM.Eight horses exercised to fatigue were used to characterize the resulting changes in blood pH, in blood lactate, free fatty acid, bicarbonate, and ammonia concentrations, and in muscle glycogen concentrations. The exercise test was conducted at a speed of 4.5 m/s on a motorized equine treadmill set at a 9% grade. At fatigue, all variables differed significantly (P less than 0.05) from base-line values. Heart rate averaged 191.1 +/- 6.5 beats/min at fatigue, and the plasma lactate concentrations increased from 7.8 +/- 0.95 mg/dl to 94.3 +/- 19.2 mg/dl. Ammonia concentrations increased from 66.7...
Hawkins JF, Tulleners EP, Evans LH, Orsini JA.Between 1979 and 1992, the alar folds were resected bilaterally in 22 horses and unilaterally in 2 horses. Abnormal respiratory tract noise and exercise intolerance were the primary complaints prior to surgery. Significantly (P = 0.01) more Standardbreds underwent resection of the alar folds, compared with the number of Standardbreds in the hospital population during the same period. The alar folds palpated abnormally thick in 13 horses and normal in 11 horses. Temporary dilatation of the nares with mattress sutures or clips lessened the respiratory tract noise and improved exercise tolerance ...
Zentek J.In this case report on myopathies in 6 saddle-horses, a combined dietary vitamin E and selenium deficiency is presumed. Other disorders, such as exertional myopathy ("Monday morning disease") due to excessive energy intake or ionophore intoxication could be excluded by calculating the energy supply or by a simple colour test. The selenium requirement of horses is estimated to 0.1-0.2 mg/kg dry matter (Meyer 1986). If natural feed compounds are low in selenium, adequate amounts of this trace element can be supplied by means of supplemental feeds, sodium selenite (20 mg/500 kg BW/week) or bruise...
Aramaki S, Suzuki E, Ishidaka O, Momose A.The effects of exercise on the metabolism of caffeine (CA) were studied 3h after administration of the drug to race horses which then underwent exercise sets (1000-m gallop). Analysis was made of pharmacokinetics of CA, changes in its plasma concentrations, its metabolites, i.e., theophylline (TP), theobromine (TB) and paraxanthine (PX), and the molar concentration ratios of CA to these metabolites. After exercise, AUC and t1/2 tended to decrease, and the concentration of CA decreased, while the concentrations of TP and TB significantly increased. The TP/CA ratio and TB/CA ratio significantly ...
Peters LW, Smiet E, de Sain-van der Velden MG, van der Kolk JH.Acylcarnitines play an important role in fuel metabolism in skeletal muscle. Objective: To assess acylcarnitine ester utilization by the hindlimb of horses at rest and following low intensity exercise and carnitine supplementation. Methods: Acylcarnitine ester uptake by the hindlimb was investigated using the arteriovenous difference technique. Blood from six warmblood mares (mean age 12 ± 3 (SD) years and weighing 538 ± 39 kg) was collected simultaneously from the transverse facial artery and from the caudal vena cava. Food was withheld for 12 hours prior to exercise. Exercise comprised a s...
Jose-Cunilleras E, Hinchcliff KW, Lacombe VA, Sams RA, Kohn CW, Taylor LE, Devor ST.Fatiguing exercise substantially decreases muscle glycogen concentration in horses, impairing athletic performance in subsequent exercise bouts. Our objective was to determine the effect of ingestion of starch-rich meals after exercise on whole body glucose kinetics and muscle glycogen replenishment. In a randomized, cross-over study seven horses with exercise-induced muscle glycogen depletion were either not fed for 8 h, fed half of the daily energy requirements ( approximately 15 Mcal DE) as hay, or fed an isocaloric amount of corn 15 min and 4 h after exercise. Starch-rich meals fed after e...
Meijer AE, van den Hoven R.In this communication, the results of a histochemical and biochemical enzyme study on gluteus medius muscle of horses, sensitive to exertional myopathy, during attacks of rhabdomyolysis are presented. For the biochemical study the biopsy specimens investigated were selected by means of histological and enzyme histochemical staining methods. Dissected specimens were used which contained groups of muscle fibres with a high or low activity of glucose-6-phosphate dehydrogenase. The activity of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, glutathione reductase, glutathione per...
