Kinematic studies of western pleasure horses are limited and were performed before current changes in the stock breed association judging standards on the western pleasure gaits. The objective was to measure the kinematics of the jog and lope of the stock breed western pleasure horse. Reflective markers attached along palpation points of the joint centres of the left forelimb and hind limb of four stock breed western pleasure horses were tracked for five strides for each gait for each horse. Both the jog and lope were determined to be four-beat stepping gaits. During the jogging stance, the elbow (159.7 ± 6.6°), carpal (179.9 ± 1.1°), fore (227.6 ± 2.7°) and hind fetlocks (227.4 ± 6.9°), stifle (159.5 ± 6.5°) and tarsal (166.5 ± 6.5°) joints demonstrated peak extension. The same joints demonstrated during swing peak flexion with the hind fetlock joint having double peaks of flexion (195.7 ± 3.2°, 182.3 ± 2.1°). During loping stance, the elbow (153.4 ± 4.2°), carpal (179.7+0.4°), and fore (228.3 ± 9.7°, 229.8 ± 10.0°) and hind fetlock (232.1 ± 2.6°) joints of the leading limbs demonstrated peak extension with tarsal peak extension (157.0 ± 9.6°) occurring at lift-off. Peak flexion occurred during swing for the elbow (105.1 ± 3.1°), carpus (119.8 ± 6.1°), hip (83.5 ± 5.4°), stifle (129.8 ± 9.6°) and tarsus (127.5 ± 6.1°). Kinematic measurements will assist in objectively defining the stock breed western pleasure gaits.

l-Carnitine supplementation can stimulate erythropoiesis, reduce exercise-induced plasma lactate concentrations and decrease post-exercise muscle damage. Next to horses, Greyhounds represent the premier animal racing species and perform short-duration, very high-intensity exercise that has the potential to incur substantial muscle damage. Under resting and standard racing conditions (5/16 mile), we tested the novel hypotheses that l-carnitine supplementation in Greyhounds would: (1) elevate haematocrit at rest and immediately post-exercise; (2) reduce peak post-exercise plasma lactate; and (3) reduce indices of muscle damage (plasma creatine phosphokinase, CPK and aspartate aminotransferase, AST). Six conditioned Greyhounds (30.1 ± 1.6 kg) underwent a randomized placebo-controlled crossover study to determine the effects of 6 weeks of l-carnitine supplementation (100 mg kg− 1 of body weight/day) at rest and following a maximal speed 5/16 mile race. In accordance with our hypotheses, l-carnitine elevated resting and immediately post-race haematocrit (control, 60.1 ± 1.7, l-carnitine, 63.6 ± 1.7; P < 0.05) and reduced peak post-race plasma CPK and AST concentrations (both P < 0.05). Those dogs with the highest peak post-exercise plasma CPK concentrations under placebo conditions evidenced the greatest reduction with l-carnitine supplementation (r = 0.99, P < 0.01). However, contrary to our hypotheses, l-carnitine did not change peak post-exercise plasma lactate concentrations (control, 27.0 ± 2.1, l-carnitine, 27.7 ± 1.3; P>0.05). We conclude that l-carnitine supplementation increases the potential for oxygen transport and reduces plasma indicators of muscle damage, CPK and AST in racing Greyhounds.

East African athletes now dominate international distance running events from the 800 m to the marathon. Explanations for their phenomenal success have included optimal environmental conditions for developing distance running performance, psychological advantage and advantageous physiological characteristics. It is well established that genetics plays a role in determining inter-individual differences in exercise performance and adaptation to training stimuli. It is not known, however, to what extent inter-population differences (i.e. between ‘races’ and/or ethnic groups) in exercise performance can be attributed to genetics. There have been considerations that ‘black’ athletes are genetically adapted towards performance, given the concurrent success of athletes of West African ancestry in sprint events. However, the current notion of ‘race’ is not universally accepted, and genetic differences within and between populations are not clearly delineated by geographical or ethnic categorizations. Recent findings from mitochondrial DNA show that the populations from which Ethiopian athletes are drawn have not been isolated populations and are not genetically distinct from other Ethiopians. Y-chromosome analysis of the same population shows concurrent results, although some differences are present between athletes and the general Ethiopian population, suggesting an influence of the Y chromosome on athlete status in Ethiopia. It is concluded that there may be a role for genetics in the success of East African athletes; however, any genetic component to their success is unlikely to be limited to East Africans and is more likely to be found in other populations. At present it is unjustified to implicate a role for genetics in the success of East African runners when no genes have been identified as being important to their performance.

When a human begins to move or locomote, the energetic demands of its skeletal muscles increase abruptly and the oxygen (O2) transport system responds to deliver increased amounts of O2 to the respiring mitochondria. It is intuitively reasonable that the rapidity with which O2 transport can be increased to and utilized by (VO2) the contracting muscles would be greater in those species with a higher maximal VO2 capacity (i.e., VO2max). This review explores the relationship between VO2max and VO2 dynamics or kinetics at across a range of species selected, in part, for their disparate VO2max capacities. In healthy humans there is compelling evidence that the speed of the VO2 kinetics at the onset of exercise is limited by an oxidative enzyme inertia within the exercising muscles rather than by VO2 delivery to those muscles. This appears true also for the horse and dog but possibly not for a certain species of frog. Whereas there is a significant correlation between VO2max and the speed of VO2 kinetics among different species, it is possible to identify species or individuals within a species that exhibit widely disparate mass-specific VO2max capacities but similar VO2 kinetics (i.e., superlative human athlete and horse).

This study aimed to produce a weight-independent algorithm for determination of body surface area (BSA; cm2) to within 5% accuracy of the directly determined value in selected horses and ponies under field conditions. Quantification of BSA in equines has applications in the fields of energy budgeting, growth, thermoregulation, conformation and drug kinetics. A simple algorithm for determining BSA to ±5% accuracy was produced for Shetland ponies, Shire horses, Welsh Mountain Section A ponies and Hanoverian mature horses and foals. The accuracy of the method was ±8% for Welsh Mountain-type ponies and Hanoverian two-year-olds. The data were produced by tiling of the shoulder region on one side of the animal with chalk and adapting a simple geometrical integrative technique. Linear anthropometric measurements were of limited use in predicting BSA in that they produced algorithms of ±5% accuracy for ponies of uniform conformation only (Welsh Mountain Section A ponies). The relevant equations were:for Arab-based breeds (Welsh Mountain-type and Section A ponies and Hanoverian horses and foals) andfor UK native breeds (Shetland ponies and Shire horses), where ‘surface area of shoulder region on one side’ was defined by the anterior margins of the supraspinatus and deep pectoral, and the posterior margin of the triceps muscles. This tiling procedure fulfilled the aim of the study and also provided quantitative information on proportional differences in areas of body regions between and within these selected breeds.

This study examined the changing levels of air pollution at major racetracks in the United States over the past 35 years of Grade I Stakes Thoroughbred racing (n = 675) to evaluate the impact on race performance. Information on winning race times, race speed, temperature, track conditions, ozone and particulate matter was analysed using multiple regression and ANOVA. The 8, 9 and 12 furlong races showed slight improvement in winning times over the 35-year time span. Although there was no significant difference in mean race speed in terms of particulate matter (F4,112 = 0.514, α < 0.05), the few races run under ‘hazardous’ ozone levels, based on the Pollutants Standards Index, were markedly slower (F4,251 = 12.365, α < 0.05). A multiple regression analysis of six additional pollutants in the Californian races revealed no significant effects beyond a slight improvement in the 7 furlong races, with decreased nitrogen dioxide levels. Of the nine racetracks with 9 furlong races, winning times in Pimlico and Belmont were approximately 4 s slower than average. Belmont also had the greatest percentage of races with hazardous ozone conditions. Other correlations between year, pollutants and improvements in race time were of small magnitude and may be an artefact of the sample size rather than of true predictive value. While racing under high levels of certain pollutants appears detrimental to equine athletes, very few races are run under these conditions and other factors such as breeding, training and individual variation may play a more significant role than this study could document with respect to pollution.

The aim of the present study was to quantify the inter-day reliability of force platform data from horses at the trot. The subjects were ten horses judged to be sound on the basis of clinical evaluation and similarity of ground reaction force peaks of left and right limbs. The same handler trotted horses in hand for four consecutive days over a force platform at their natural and comfortable velocity between 2.70 and 3.60 m s−1. For each horse, velocity was controlled in a range of±0.15 m s−1. Five contacts per limb were recorded on each day. Custom-written code in MATLAB was used to smooth the data and time-normalize to 101 data points. The agreement boundary was used to determine the reliability of seven force variables. Stance duration, peak vertical force and vertical impulse were the most reliable variables (<10% variability in the mean), while peak braking and propulsive forces and impulses had larger variation across the three days (>20% variability in the mean). Variables with low variability may require fewer animals, trials and days to obtain accurate data while maintaining adequate statistical power. These results may act both as a reference when studying variability in lame horses and as a guide for planning future equine kinetic studies.

The fatigue of high-intensity exercise is now believed to reside primarily within the excitation–contraction coupling processes associated with the plasma membrane of skeletal muscle (sarcolemm) and calcium-mediated events leading to myofilament sliding. This paper summarizes recent developments and advances in the identification of factors that contribute to changes in sarcolemmal excitability of mammalian skeletal muscle as a consequence of high-intensity exercise. There is an increasing recognition of the probable role that is played by the transverse tubular system (T-system), a system that comprises c. 80% of the total sarcolemmal surface capable of ion exchange. Furthermore, the fluid within the T-system has limited access to interstitial fluid bathing myofibres; hence, T-system fluid is probably markedly different from interstitial fluid during high-intensity exercise. Mechanically skinned fibre preparation is providing many new insights into functions of the surface membrane and T-system in fatigue. A scenario is developed whereby accumulation of potassium within the T-system ([K+]o) contributes to reduced membrane excitability, as well as lowering of T-system sodium and chloride, concomitant with loss of intracellular potassium ([K+]i) and accumulation of intracellular sodium ([Na+]) and chloride ([Cl−]). Lowering the [Na+]o/[Na+]i ratio and raising myoplasmic [Na+]i have been shown to decrease membrane excitability and impair action potential propagation. Maintained high [Cl−]o may also have a protective effect in maintaining membrane excitability, and this effect appears to be very pronounced in the presence of raised [K+]o. In contrast to dogma associating high [H+] to fatigue, recent studies have also shown that induced acidosis that results in increased [H+]o and [H+]i restores force production in muscles and skinned fibres fatigued by intermittent tetanic stimulation. This effect may be due to a decrease in surface membrane Cl− permeability that serves to restore membrane excitability. During high-intensity exercise, simultaneous changes in trans-membrane ion concentrations and membrane ion conductances may serve to reduce impairment of membrane excitability that provides for a maintained, though reduced, contractile function.

The purpose of the present study was to determine the influence of fitness on cardiac function, particularly on left ventricular function parameters. Fifteen healthy ‘three-day event’ warmblood horses were examined at rest and immediately after high-speed treadmill exercise (3% incline, 3 min 1.8 m s−1, 3 min 4 m s−1, 3 min 5 m s−1, 3 min 6 and 3 min 7 m s−1, 1.5 min 8 m s−1). Horses were divided into two groups. Group 1 consisted of nine conditioned horses and group 2 included six unconditioned horses. Left ventricular dimensions and function were acquired using standardized echocardiographic indices. To assess the level of fitness, heart rate and blood lactate concentration were determined at rest and immediately after exercise. The group of conditioned horses showed a significantly lower blood lactate concentration (mean value 2.39 mmol l−1) after high-speed treadmill exercise than did the group of unconditioned horses (mean value 3.81 mmol l−1), which clearly revealed the difference in fitness between the two groups. During exercise the heart rate was not significantly different between both groups. Only in the recovery phase did the trained horses show a significant faster decrease in heart rate than did the untrained horses. Mean heart rate during echocardiography immediately after exercise (within the first 2 min) was 105 bpm in the group of trained horses and 113 bpm in the group of untrained horses.Within each group of horses, several echocardiographic parameters differed significantly between resting values and values after treadmill exercise. Particularly, in the group of trained horses, 17 out of 30 echocardiographic parameters (most diastolic) differed significantly between rest and exercise. In the group of untrained horses, only six out of 30 parameters were significantly different. At rest, left ventricular diameter at the apex cordis, left ventricular free wall at papillary muscle level, left ventricular volume and stroke volume, as well as fractional shortening (at the apex cordis and at papillary muscle level) were significantly different between both groups. After treadmill exercise comparison of echocardiographic parameters of the conditioned to those of the unconditioned animals showed no significant differences. In the present study, data have been provided for stress echocardiography in conditioned and unconditioned warmblood horses without any disorders of the cardiovascular system.

Carbohydrate and fat are the predominant sources of energy during exercise in mammals. Carbohydrates, such as muscle glycogen and plasma glucose, and fats from adipose tissue and intramuscular triglycerides are oxidized during exercise in amounts and proportions that vary depending on the exercise intensity, level of fitness and nutritional status. In horses, muscle glycogen, and to a lesser extent plasma glucose, are oxidized in substantial amounts during low-, moderate- and high-intensity exercise. Carbohydrate availability to skeletal muscle affects exercise performance in humans, however this relationship is not well outlined in horses. Glucose supplementation by intravenous administration during exercise in horses increases duration of moderate-intensity exercise. However, the effect of glucose supplementation by ingestion of a soluble carbohydrate-rich meal prior to exercise on athletic performance has not been established in horses. Low muscle glycogen concentrations prior to exercise in horses are associated with decreased time to exhaustion at moderate- and high-intensity exercise. Nutritional interventions intended to enhance muscle glycogen resynthesis have proved less successful in horses than in other species. Replenishment of muscle glycogen after strenuous exercise in horses is not complete until 48–72 h after exercise, whereas in humans and laboratory animals it is complete by 24 h. The slower rate of muscle glycogen replenishment after exercise in horses may be related to an inherent lower ability to digest starch and other sources of glucose, a lower ability to synthesize muscle glycogen, or both. The aim of this review is to describe the present understanding of carbohydrate metabolism in the exercising horse, its implications on nutrition and athletic performance, and to contrast it with that in other species.

Measurement and interpretation of acid–base status are important in clinical practice and among racing jurisdictions to determine if horses have been administered alkalinizing substances for the purpose of enhancing performance. The present study used the physicochemical approach to characterize the daily variation in plasma electrolytes and acid–base state that occurs in horses in the absence of feeding and exercise. Jugular venous blood was sampled every 1–2 h from two groups (n=4 and n=5) of Standardbred horses over a 25 h period where food and exercise were withheld. One group of horses was studied in October and one in December. The time course and magnitude of circadian responses differed between the two groups, suggesting that subtle differences in environment may manifest in acid–base status. Significant daily variation occurred in plasma weak acid concentration ([Atot]) and strong ion difference ([SID]), [Cl−], [K+], [Na+] and [lactate−], which contributed to significant changes in [H+] and TCO2. The night-time period was associated with a mild acidosis, marked by increases in plasma [H+] and decreases in TCO2, compared with the morning hours. The night-time acidosis resulted from an increased plasma [Atot] due to an increased plasma protein concentration ([PP]), and a decreased [SID] due to increases in [Cl−] and decreases in [Na+]. An increased plasma [K+] during the night-time had a mild alkalotic effect. There were no differences in pCO2. It was concluded that many equine plasma electrolyte and acid–base parameters exhibit fluctuations in the absence of feeding and exercise, and it is likely that some of these changes are due to daily variation.

Humans undergoing intense exercise exhibit transient microalbuminuria. Previous studies have shown that swimming, but not running, induces microalbuminuria in dogs. In this study, urine samples were collected from nineteen well-conditioned Alaskan sled dogs and analysed by the Heska ERD-Screen Test for microalbuminuria. None of the dogs has microalbuminuria, indicated that well-trained dogs do not develop microalbuminuria after running. Further studies are needed to determine if these dogs do develop microalbuminuria after competition or longer-distane runs.

Eventing is a three-phased discipline with a stratified progressive performance structure. Sample data (10%) were analysed from all horses competing within the UK (n = 53 890) during 2003 at all five levels of competition (intro, pre-novice, novice, intermediate, advanced). Five performance penalty score contributors were examined (dressage score, show jumping time faults, show jumping jump faults, cross-country jumping faults and cross-country time faults – independent variables) with regard to their effect on final ranking in competition (dependent variable). Percentage accruement of penalty points showed dressage to be the largest contributor (69%) at the intro level, falling to 53% at the advanced level. The show jumping phase was the smallest percentage contributor (greatest influence seen at the novice level, 9%). The influence of cross-country increased as the level of competition became more difficult (greatest at the advanced level, 42%). Linear regression analysis was undertaken with the use of a standardized linear model. The models accounted for between 75 and 83% of all variance dependent on level. Accession of data to the model was almost identical from novice level upwards, with cross-country time and dressage faults exerting the greatest influence. At the lower levels of competition a more complex picture of accession was observed. The use of regression analysis supported the stated sporting aims of eventings governing bodies.

Osteocalcin (OC), bone fraction of alkaline phosphatases (BAP) and hydroxyproline (HOP) are markers of bone cell activity. The kinetics of these markers and the analysis of their variations could be related to the osteoarticular status (OAS) of young horses. The growth of Thoroughbreds, French Trotters and Selle Français horses was followed up to 18 months. Blood samples were taken regularly to measure OC, HOP and BAP by standardized techniques. The OAS was evaluated by radiographic examination of the limbs. Based on radiographic findings, two groups of horses were investigated, with no lesions or severely affected. Analysis of variance was used to detect the effects of age and breed, and OAS on parameters. The logarithmic model was used to determine the kinetics of the markers. A rapid decrease in marker concentrations with age and differences between breed was observed. At birth, BAP, OC and HOP concentrations were significantly higher in normal horses (1910 UI l− 1, 192 ng ml− 1 and 35 mg l− 1, respectively) than in horses with severe lesions (1620 UI l− 1, 149 ng ml− 1 and 24 mg l− 1, respectively). During the first 6 months, OC, HOP and BAP remained lower in severely affected horses.

Gaited horse research is limited, with the majority of the research focusing on the measurement of the temporal variables of adult-gaited horses. The objective was to measure the fore and hind limb kinematics of the flat-walking Tennessee Walking Horse (TWH) yearling. Four TWH yearlings were filmed at 60 Hz being led at a consistent flat walk that followed breed standards. Reflective markers attached along palpation points of the joint centres of the fore and hind limbs were tracked for five strides for each yearling. During stance, the elbow (154±3°), carpal (185±3°), fore (222±9 and 221±9°) and hind fetlocks (216±11°), hip (111±3°), stifle (157±4°) and tarsal (167±9°) joints demonstrated peak extension with the forelimb fetlock joint having double peaks of extension. During swing, the same joints demonstrated peak flexion with the elbow (109±3°) and hip (88±6°) peak flexion occurring later in the swing phase. The carpal (54±4°) joint demonstrated a greater range of motion than the tarsus (40±9°) with less vertical displacement. The hind fetlock (60±10°) had greater range of joint motion compared with the forelimb fetlock (45±8°), but lacked the double peak of extension during swing. Kinematic measurements will assist in objectively defining the gait for both clinical and performance applications.

Physiological studies of elite and sub-elite black South African runners show that these athletes are typically about 10–12 kg lighter than white athletes and that they are able to sustain higher exercise intensities for longer than white runners. Such superior performance is not a result of higher V O2max values and hence cannot be due to superior oxygen delivery to the active muscles during maximal exercise, as is predicted by the traditional cardiovascular/anaerobic/catastrophic models of exercise physiology. A marginally superior running economy is also unlikely to be a crucial determinant in explaining this apparent superiority. However, black athletes are able to sustain lower rectal and thigh, but higher mean skin, temperatures during exercise. Furthermore, when exercising in the heat, lighter black athletes are able to maintain higher running speeds than are larger white runners matched for running performance in cool environmental conditions. According to the contrasting theory that the body acts as a complex system during exercise, the superiority of black African athletes should be sought in an enhanced capacity to maintain homeostasis in all their inter-dependent biological systems despite running at higher relative exercise intensities and metabolic rates. In this case, any explanation for the success of East African runners will be found in the way in which their innate physiology, training, environment, expectations and genes influence the function of those parts of their subconscious (and conscious) brains that appear to regulate the protection of homeostasis during exercise as part of an integrative, complex biological system.

Scientific investigation of racial athletic aptitude has been preceded by a century of pseudo- and quasi-scientific speculations on this topic. For this reason, physiological and anatomical research on African runners is performed in a social context that is still permeated by folkloric ideas about racial differences, some of which pertain to athletic performance. A powerful stereotype of ‘tropical nature’ and its ‘superabundant’ vitality has influenced non-African thinking about African athletic potential. The idea that evolutionary adaptation in Africa is a particularly severe version of natural selection has had a similar effect on Western thinking about African runners. Romantic ideas about African athletic aptitude may, therefore, be understood as modern versions of the doctrine of black ‘hardiness’ that survives in contemporary biomedicine in various forms.

Diminished basal plasma cortisol concentrations and a blunted cortisol response to exercise have been observed in human asthmatics. In horses with recurrent airway obstruction (RAO), plasma concentrations of cortisol at rest are not significantly different from those of healthy horses, but the effect of exercise on endogenous cortisol concentrations has not been described. Ascorbic acid is a non-enzymatic antioxidant with proposed immune-modulating properties. In man, supplementation with ascorbic acid has been shown to attenuate the exercise-induced increase in plasma cortisol following prolonged, submaximal exercise. The relationship between cortisol and ascorbic acid has not previously been investigated in the horse. In a blinded cross-over design, five horses with RAO and six healthy non-RAO controls performed a standard exercise test following 4 weeks of supplementation with either an antioxidant (providing 10 mg ascorbic acid kg−1 day−1) or a placebo (<1 mg ascorbic acid kg−1 day−1). Venous blood samples were obtained 1 h prior to exercise and at 0, 15, 60 min and 24 h thereafter. Exercise resulted in a significant increase in plasma cortisol concentrations in both groups of horses (P<0.05). Basal and post-exercise concentrations of plasma cortisol in the RAO group (136±16 and 210±16 μmol l−1, respectively) were not significantly different from those in the non-RAO group (129±43 and 218±30 μmol l−1, respectively). Antioxidant supplementation increased basal and post-exercise concentrations of plasma ascorbic acid in RAO and non-RAO horses (P<0.05) but had no effect on plasma cortisol concentration in either group, before or after exercise (RAO: rest 157±27 μmol l−1, post-exercise 222±21 μmol l−1; non-RAO: rest 140±11 μmol l−1, post-exercise 227±35 μmol l−1). In conclusion, RAO-affected horses in remission demonstrate the same cortisol response to exercise as healthy controls. Antioxidant supplementation had no impact on post-exercise concentrations of plasma cortisol in either healthy or RAO-affected horses in remission.

Genes undoubtedly play a role in the development of a successful athlete. This view has flourished on anecdotes such as the observation of a child who displays the same aptitude for a particular sport as one of their parents, or a pair of sisters who both excel in the same discipline. However, the conclusions made from this type of observation have an obvious limitation: that similar environmental factors may be just as responsible as genetic inheritance in explaining the passage and sharing of talent between family members. Here, we review briefly the salient data showing that genes do play a role in athletic performance, and although the data examining the effect of specific genes are limited, we present data examining the role of the angiotensin-converting enzyme gene in human physical performance.

Temporal stride characteristics of the canter were compared between performance-shod (PS) and light-shod (LS) Tennessee Walking Horses, which generally differ in training and shoeing methods. Four consecutive strides for ten PS and ten LS horses were filmed (30 Hz), and frame-by-frame analysis performed to determine stride duration and individual limb stance duration. Also analysed was the percentage of stride duration devoted to single, bipedal or tripedal limb support. Footfall sequence for PS was trailing hind (TrH), leading hind (LdH), trailing fore (TrF) and leading fore (LdF), whereas footfall sequence for LS horses varied, with the majority of LS performing a sequence of TrH–TrF–LdH–LdF. Stride duration was greater for PS. As a percentage of stride duration, PS demonstrated greater duration of TrF and LdF, while LS demonstrated greater LdH duration. Hind and fore single limb support, and tripedal support, were greater for LS; however, PS utilized bipedal support to a larger extent than LS. Hind or forelimb bipedal support was demonstrated only in PS, while only LS demonstrated lateral bipedal support. Thus, while both performance- and light-shod Tennessee Walking Horses perform the canter, temporal variables for this gait differ dramatically between the two groups.