Topic:Exercise Physiology
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.
V(O2) recovery kinetics in the horse following moderate, heavy, and severe exercise. At the onset of exercise, horses exhibit O2 uptake (VO2) kinetics that are qualitatively similar to those of humans. In humans, there is a marked dissymmetry between on- and off-kinetics for VO2. This investigation sought to formally characterize the off-transient (recovery) VO2 kinetics in the horse within the moderate (M), heavy (H), and severe (S) exercise domains. Six horses were run on a high-speed treadmill at M, H, and S exercise intensities (i.e., that speed which yielded approximately 50, 85, 100% peak VO2, respectively, on the maximal incremental test). The time courses for the recov...
Locomotor, cardiocirculatory and metabolic adaptations to training in Andalusian and Anglo-Arabian horses. The effects of two training programmes in 20 Andalusian and 12 Anglo-Arabian horses were evaluated by an increasing intensity work test at velocities of 4, 5, 6, 7 and 8 m sec(-1). Heart rate was monitored and blood samples were drawn at rest and after each velocity to analyse packed cell volume, haemoglobin concentration, plasma lactate and potassium levels. Furthermore, the programmes were video-taped and stride length, duration and frequency, stance (restraint and propulsion), swing phase durations and stride vertical component were measured. The training protocol of the Andalusian horses p...
Methods, applications and limitations of gait analysis in horses. Over the last 30 years, the increase in interest in horses for racing and riding activities has stimulated scientific research in equine locomotion. This paper presents a review of the measurement methods and their applications used to assess equine locomotion. After describing gaits and velocity-related changes in stride variables, the current applications of gait analysis are presented. The economic consequences of lameness justifies the great effort now being put into lameness quantification and prevention. To improve breeding and reduce the costs of training, early performance evaluation t...
Morphometric study of the equine navicular bone: variations with breeds and types of horse and influence of exercise. Navicular bones from the 4 limbs of 95 horses, classified in 9 categories, were studied. The anatomical bases were established for the morphometry of the navicular bone and its variations according to the category of horse, after corrections were made for front or rear limb, sex, weight, size and age. In ponies, navicular bone measurements were smallest for light ponies and regularly increased with body size, but in horses, navicular bone dimensions were smallest for the athletic halfbred, intermediate for draft horse, thoroughbreds and sedentary halfbreds and largest for heavy halfbreds. The ...
Cardiovascular and metabolic adaptations in horses competing in cross-country events. The cardiovascular and metabolic response to two cross-country events (CC*: preliminary level and CC*** advanced level) were analysed in 8 male eventing horses (4 Anglo-Hunter and 4 Anglo-Arabian). This study focused on the establishment of the main metabolic pathways involved in the muscle energy resynthesis during the competitions. Heart rate (HR) was recorded throughout the CC events. Jugular venous blood samples were withdrawn before the warm-up period, immediately after the competitions and at 5 and 10 min in the recuperation period. The following haematological parameters were studied: r...
Skeletal muscle metabolic response to exercise in horses with ‘tying-up’ due to polysaccharide storage myopathy. Polysaccharide storage myopathy (PSSM) is a distinct cause of exertional rhabdomyolysis in Quarter Horses that results in glycogen and abnormal polysaccharide accumulation. The purpose of this study was to determine if excessive glycogen storage in PSSM is due to a glycolytic defect that impairs utilisation of this substrate during exercise. Muscle biopsies, blood lactates and serum CK were obtained 1) at rest from 5 PSSM Quarter Horses, 4 normal Quarter Horses (QH controls) and 6 Thoroughbreds with recurrent exertional rhabdomyolysis (TB RER) and 2) after a maximal treadmill exercise test in ...
Effects of inhaled dry powder ipratropium bromide on recovery from exercise of horses with COPD. The present study evaluated ventilatory, cardiovascular and metabolic parameters during recovery from strenuous exercise in horses suffering from a crisis of chronic obstructive pulmonary disease (COPD) and to determine whether ipratropium dry powder inhalation (DPI) before exercise has an effect on these parameters. When 6 saddle horses, affected with COPD, developed airway obstruction, they inhaled placebo and ipratropium (2400 microg/horse), the order being randomly chosen. Pulmonary function tests were then recorded 15 min after inhalation. Following these tests, the horses underwent a str...
Physiological responses of horses to a treadmill simulated speed and endurance test in high heat and humidity before and after humid heat acclimation. To investigate whether horses were able to acclimate to conditions of high temperature and humidity, 5 horses of different breeds were trained for 80 min on 15 consecutive days on a treadmill at 30 degrees C and 80%RH. Training consisted of a combination of long duration low-intensity exercise, medium duration medium intensity exercise and short duration high intensity exercise. Between training sessions the horses were maintained at 11+/-3 degrees C and 74+/-2%RH. Before (PRE-ACC) and after acclimation (POST-ACC) the horses undertook a simulated Competition Exercise Test (CET), designed to re...
Effect of rider and riding style on deformation of the front hoof wall in warmblood horses. A rider modifies the weight distribution and dynamic balance of the horse. But what effect does a rider have on the mechanical behaviour of the hoof during each stance phase? Does riding style have any effect on this behaviour? We attempted to answer these questions using strains recorded from 5 rosette strain gauges glued to the surface of the front hooves of 4 Warmblood horses. Comparisons were made between strains with and without a rider, and when the rider was sitting, rising at a trot, or in a forward seated position. The change in strains from trot to lead or nonlead at a canter, and th...
Variation in surface strain on the equine hoof wall at the midstep with shoeing, gait, substrate, direction of travel, and hoof shape. Objectives were to examine the deformation of the healthy equine front hoof during locomotion, by recording strains on its outer surface, and to test whether its mechanical behaviour is significantly altered under different locomotory conditions and variation in hoof shape. Strains were recorded in vivo from 5 rosette gauges around the circumference of the right forehooves of 12 horses. The magnitudes and orientations of principal strains at the midstep were compared statistically for different conditions of shoeing (shod vs. unshod), gait (walk vs. trot), substrate (treadmill vs. ground), and...
Sarcoplasmic reticulum responses to repeated sprints are affected by conditioning of horses. Sarcoplasmic reticulum (SR) responses to repeated sprints and to physical conditioning were studied in 10 Quarter Horses. Exercise tests (four repeated sprints on a treadmill) were conducted before and after 12 wk of sprint conditioning. Muscle samples from the middle gluteal muscle were taken before and after each exercise test, and SR vesicles were isolated. Calcium uptake was determined spectrophotometrically using antipyrylazo III, and Ca2+-ATPase activity was determined using an enzyme-linked optical assay. Conditioning increased calcium uptake rate and Ca2+-ATPase activity by 14 and 38%,...
Effect of regular training on the myocardial and plasma concentrations of taurine and alpha-amino acids in thoroughbred horses. Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 +/- 1.2 mumol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 +/- 0.9 and 7.7 +/- 0.69 mumol/g wet weight for glutam...
Effects of exercise and EDTA administration on blood ionized calcium and parathyroid hormone in horses. To determine effects of exercise on blood ionized calcium (Ca2+) and plasma parathyroid hormone (PTH) concentrations in horses and to compare the effects of exercise-induced and EDTA-induced hypocalcemia on PTH secretion. Methods: 17 horses entered in a show jumping competition and 5 horses given EDTA. Methods: Blood Ca2+ and plasma PTH concentrations were measured before and after exercise in the 17 horses entered in the jumping competition. In the other 5 horses, concentrations were measured during infusion of EDTA IV. Results: Exercise resulted in a significant decrease in blood Ca2+ concen...
Angular kinematic patterns of limbs in elite and riding horses at trot. Normal speed videography was used to determine the angular parameters of 28 Spanish Thoroughbreds at trot. Horses were divided into 3 groups: Group UT, comprising 9 animals (provided by the VII National Stud, Cordoba, Spain) which had undergone no specific training programme and which were hand led at the trot; Group T, formed by 19 horses considered to be highly bred and trained, and which were also hand led; and Group RT, comprising the same horses as the latter group but this time trotted by a rider. Each animal was filmed 6 times from the right-hand side, using a Hi8 (25 Hz) video camera. ...
Muscle anaerobic response to a maximal treadmill exercise test in Standardbred trotters. The purpose of this study was to develop a standardised maximal treadmill exercise test performed until fatigue in order to find reproducible markers for anaerobic metabolism, specifically adenine nucleotide degradation. Six Standardbred trotters performed an incremental maximal treadmill exercise test in 1 min steps (starting with 7 m/s) until they could no longer keep pace with the treadmill. The test was performed twice with at least one week between the tests. Heart rate was recorded and venous blood samples were obtained during the test and in the recovery period for determination of plas...
Intensity-dependent effects of acute submaximal exercise on the pharmacokinetics of bromsulphalein in horses. To determine the effects of acute exercise on hepatic blood flow by studying hepatic clearance of bromsulphalein for several submaximal exercise intensities. Methods: 8 adult Standardbred mares. Methods: Horses were subjected to 4 submaximal exercise intensities (resting and 40, 60, and 80% maximal oxygen consumption). After horses had been running at the required treadmill speed for 1 minute, bromsulphalein (BSP; 5 mg/kg of body weight, IV) was administered during a 45- to 60-second period, and horses continued at the desired speed for an additional 15 minutes. Blood samples were collected at...
Hepatic blood flow in horses during the recuperative period from maximal exercise. To determine effects of walking or standing on hepatic blood flow of horses after brief, intense exercise. Methods: 6 adult Thoroughbreds (4 mares, 2 geldings). Methods: Horses were preconditioned on a treadmill to establish uniform level of fitness. Once fit, treadmill speed causing each horse to exercise at 120% of maximal oxygen consumption was determined and used in simulated races at 14-day intervals. In a three-way crossover study, horses were exercised at a speed inducing 120% of maximal oxygen consumption until fatigued or for a maximum of 2 minutes. Three interventions were studied: r...
The influence of speed and height at the withers on the kinematics of sound horses at the hand-led trot. The influence of speed and height at the withers on some biokinematic stride parameters (linear, temporal and angular) was measured in 15 Spanish Thoroughbreds (Andalusian Purebred) trotted hand-led along a track; analysis was made of the correlation between speed and height at the withers and of some biokinematic parameters of equine locomotion. Both height at the withers and speed were positively and significantly correlated to the linear parameters examined. Temporal parameters did not reveal a significant correlation with the height at the withers. The correlations with the angular paramet...
Physical exercise, oxidative stress and muscle damage in racehorses. Since it has been suggested that lipid peroxidation following free radical overproduction may be one of the causes of physical exercise-induced myopathies and hemolysis in horses, we looked for the possible relationships between these phenomena and muscle fiber damage. We use a homogeneous group of Maremmana stallions which, after a 3-month training period, underwent a series of physical exercises of increasing intensity. We determined the contents of malondialdehyde (MDA), one of the main lipid peroxidation end-products, and glutathione the substrate of one of the most important free radical ...
Muscle-tendon stresses and elastic energy storage during locomotion in the horse. The stresses acting in muscle-tendon units and ligaments of the forelimb and hindlimb of horses were determined over a range of speed and gait based on recordings of ground reaction forces and limb kinematics. Maximum stresses of 40-50 MPa were calculated to act in several of the principal forelimb (superficial digital flexor (SDF), deep digital flexor (DDF), ulnaris lateralis (UL) and flexor carpi ulnaris/radialis (FCU/R)) and hindlimb tendons (plantaris, DDF) at the fastest galloping speeds recorded (up to 7.4 m s-1). Smaller stresses were found for the gastrocnemius (GAST) tendon (30 MPa) a...
Optimization of the mammalian respiratory system: symmorphosis versus single species adaptation. Taylor and Weibel's principle of symmorphosis hypothesized optimal design of the mammalian respiratory system, with no excess structure relative to its maximal O2 flux, VO2max. Although they found symmorphosis not to be a general principle of design, it might apply to a highly adapted aerobic athlete, e.g. the Thoroughbred racehorse. Using a mathematical model based on empirical data of the equine O2 transport system at normoxic VO2max, the fraction of the total limitation to O2 flux contributed by each of the respiratory transport steps is calculated as either the fractional change (F) in VO2...
Shear-induced platelet activation and platelet-neutrophil aggregate formation by equine platelets. To determine whether platelets become activated and form platelet-platelet or platelet-neutrophil aggregates, or both, when subjected to shear. Methods: Blood obtained from 3 Thoroughbreds. Methods: Blood, with PCV adjusted to 32 (low hematocrit) or 60 (high hematocrit)%, was subjected to shear rates of 11.25, 22.5, 45, 90, 225, and 750/s for 3 minutes by use of a cone-plate viscometer. Flow cytometric techniques were used to identify activated platelets, platelet-platelet aggregates, and platelet-neutrophil aggregates. Results: Shear resulted in decreased platelet count, increased mean platel...
Exercise-training-induced alterations in hepatic function in mares. The effects of exercise training on hepatic function in horses were determined by studying the plasma clearance of antipyrine (20 mg/kg iv) in adult mares that either underwent treadmill training for 5 wk (n = 7) or remained in box stalls for the same time period (n = 6). Training consisted of treadmill exercise at 60% (12 min/day) and 90% (3 min/day) of pretraining maximal oxygen consumption (V(O2)max) for 6 days/wk for 5 wk. V(O2)max and velocity to obtain a blood lactate concentration of 4 mmol/l were significantly increased (from 129 to 149 ml x min-1 x kg-1 and from 5.6 to 6.1 m/s, respec...
Effect of tryptophan and of glucose on exercise capacity of horses. We hypothesized that central fatigue may have a role in limiting the endurance capacity of horses. Therefore, we tested the effect of infusing tryptophan and/or glucose on endurance time and plasma concentrations of free tryptophan and other substrates thought to affect tryptophan uptake into the brain of seven mares (3-4 yr of age, 353-435 kg) that ran on a treadmill at 50% of maximal O2 consumption to fatigue. With use of a counterbalanced crossover design, the horses were infused with tryptophan (100 mg/kg in saline solution) or a similar volume of saline solution (placebo) before exercise....
Blood-gas measurements adjusted for temperature at three sites during incremental exercise in the horse. Rectal temperature (Tre) is often used to adjust measurements of blood gases, but these adjusted measurements may not approximate temperatures during intense exercise at main sites of gas exchange: muscle and lung. To evaluate differences in blood gases between sites, temperatures (T) were measured with thermocouples in the rectum (re), in mixed venous blood (v), in gluteal muscle (mu), and on the skin (sk) in seven Arabian horses as they underwent an incremental exercise test on a treadmill. Blood samples were drawn from the carotid artery and pulmonary artery (mixed venous) 30 s before each ...
A model equation for the prediction of mechanical internal work of terrestrial locomotion. By refining a previously published model, a simple equation for the estimation of the mechanical internal work during locomotion is presented. The only input variables are the progression speed, the stride frequency and the duty factor, i.e. the fraction of the stride duration at which a foot is in contact with the ground. The inclusion of this last variable, easily measurable, allows to obtain a single equation for both walking and running. The model predictions have been compared with the mechanical internal work experimentally obtained on humans in several conditions: speeds (range 0.8-3.3 ...
Selected blood parameters during recovery from strenuous running exertion in trotters. During training, in 10 trotters, blood samples from the vena jugularis were taken before and after a heat with 80% of maximum capability as well as in the recovery period. Lactic acid concentration and pH-value, haematocrit and haemoglobin content, as well as protein concentration and osmolality were measured. With the exception of protein concentration, the time course of the values during the recovery could be described by simple mathematical models (biexponential or exponential equations). Only in the case of blood lactate concentration, the basal value was not yet achieved 120 min after th...
Effect of density and weight of load on the energy cost of carrying loads by donkeys and ponies. Two experiments were designed to compare the energy used in carrying loads by donkeys and ponies. In the first experiment 3 donkeys and 3 ponies were compared on treadmills in the UK. Density of load (lead shot or straw) had no significant effect on the energy cost of carrying loads; however, the energy cost of carrying a load decreased significantly (p < 0.001) as the weight of the load increased (in donkeys 6.44, 4.35 and 3.03 J/kg load/m, in ponies 5.82, 3.75 and 3.68 J/kg load/m, for loads of 13, 20 and 27 kg/100 kg liveweight (M) respectively). Differences between species were not sign...