The purpose of this study was to determine whether significant differences exist in the position of a horse rider when assessed at different points in the horse's stride cycle at walk, trot and canter on the right rein. Video analysis was used to determine the absolute angles of the trunk, thigh and lower leg of five subjects during the walk, rising trot and canter. The range of movement of the trunk, thigh and lower leg during each gait was also determined. At walk significant differences in the rider's trunk angle were found between limb impacts (P<0.05). At trot significant differences were found in all angles between impacts of the horse's diagonal limb pairs (P<0.05). At canter, there were no significant differences in rider position between limb impacts. The range of movement of the trunk was 5.9°, 4.1° and 4.7° for walk, trot and canter, respectively. The corresponding ranges of the thigh and lower leg were 1.9°, 7.3° and 4.4°, and 2.9°, 5.2° and 3.9°, respectively. This preliminary study has demonstrated differences in rider posture between limb impacts in walk and trot. Further work is necessary to investigate the forces acting on the rider during each gait and the postural strategies employed by riders to maintain a balanced position. Such work is a necessary forerunner to the study of rider influence on horse performance.

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.

Equine and human athletic endeavour often requires near-maximal rates of aerobic metabolism. It, therefore, follows that any practical method of increasing the aerobic contribution to exercise should be of benefit to athletic performance. Prior ‘warm-up’ exercise is widely advocated before exercise performance in order to ‘prime’ the physiological mechanisms of power generation and energy supply. In the present review, we examine evidence that prior exercise, in both the horse and the human, results in marked increases in O2 supply and utilization during subsequent intense exercise. Much of this evidence stems from the study of pulmonary oxygen uptake dynamics and the related concepts of oxygen deficit and critical power. We, therefore, also review the effect of prior exercise in light of the exercise intensity domains in which the prior and subsequent exercise performances take place. Recent evidence suggests that both moderate and heavy exercise should improve subsequent severe exercise performance in both species by ∼2–3%, although much work remains to be done to establish the ‘optimal’ warm-up regime(s).

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).

The exercise performed by Thoroughbred (TB) and Standardbred (SB) racehorses is similar. Nevertheless, warm-up regimes seem to differ between trainers of the two breeds. The aim of this study was to collect some preliminary results on warm-up strategies used by trainers of SB and TB in Sweden and the physiological response to two warm-up regimes of practical relevance. A questionnaire was answered by eight and nine SB and TB trainers, respectively, and showed that the SB trainers tended to perform longer warm-ups than TB trainers. In the exercise study, a long and a short warm-up (LWU and SWU) were designed by two trainers (SB and TB, respectively) and performed prior to an intensive exercise session. The study showed that the recovery period in the LWU trial in SBs was prolonged compared with the SWU trial and associated with increased body temperature (39.6±0.3 versus 39.1±0.1°C 15 min post-exercise), heart rate, and breathing frequency (66±10 versus 55±6 beats min−1 and 86±11 versus 56±6 breaths min−1 15 min post-exercise). In addition, the body weight loss was increased by 129% compared with the SWU. In the TB trial, the post-exercise breathing frequency was higher following SWU compared with LWU (97±7 versus 71±8 breaths min−1 15 min post-exercise), indicating increased anaerobic metabolism. Although this study involves few animals, it indicated that the LWU for TBs and the SWU for SBs was most beneficial.

Exercise-induced pulmonary haemorrhage (EIPH) is a serious condition that affects the health and possibly the performance of all racehorses. However, only two treatments, furosemide and the Flair™ equine nasal strip, both of which reduce capillary transmural pressure, have been successful in reducing EIPH. Alternatively, transient impairment of platelet function and coagulation during exercise has been considered an additional contributor to EIPH. Consequently, herbal formulations designed to enhance platelet function, and hence coagulation, are hypothesized to reduce EIPH. To investigate the validity of this hypothesis, five Thoroughbred horses completed three maximal incremental exercise tests on a 10% inclined treadmill in a randomized cross-over design experiment. Treatments included twice daily oral administration (for 3 days) of a placebo (PL; cornstarch) and two herbal formulas, Yunnan Paiyao (YP) or Single Immortal (SI). Blood samples for coagulation profiles, complete blood counts and biochemistry profiles were collected before each exercise test. During each test, pulmonary arterial pressure, oxygen uptake, arterial blood gases, plasma lactate and time-to-fatigue were measured. Severity of EIPH was quantified via bronchoalveolar lavage (BAL) at 30–60 min post-exercise. The herbal formulations were not effective in decreasing EIPH (×106 red blood cells ml−1 BAL fluid: PL, 27.1±11.6; YP, 33.2±23.4; SI, 35.3±15.4, P>0.05) or in changing any of the other variables measured with the exception of time-to-fatigue, which was slightly but significantly prolonged by Single Immortal compared with placebo and Yunnan Paiyao (PL, 670±9.6 s; YP, 665±5.5 s; SI, 685±7.9 s, P<0.05). Thus, these results do not support the use of these herbal formulations in the prevention of EIPH.

The present study characterized the fluid and electrolyte shifts that occur in Standardbred racehorses during recovery from high-intensity exercise. Jugular venous blood was sampled from 13 Standardbreds in racing condition, at rest and for 2 h following a high-intensity training workout. Total body water (TBW), extracellular fluid volume (ECFV) and plasma volume (PV) were measured at rest using indicator dilution techniques (D2O, thiocyanate and Evans Blue, respectively). Changes in TBW were assessed from measures of body mass, and changes in PV and ECFV were calculated from changes in plasma protein concentration. Exercise resulted in a 26.9% decrease in PV. At 10 min of recovery TBW and ECFV were decreased by 2.2% and 16.5% respectively, while intracellular fluid volume was increased by 7.1%. There was a continued loss of fluid due to sweating throughout the recovery period such that TBW was decreased by 3.9% at 90 min of recovery. This decrease in TBW was nearly equally partitioned between the extracellular and intracellular fluid compartments. Plasma Na+ and Cl− contents were decreased at 1 min of recovery, but not different from rest by 40 min of recovery. Plasma K+ content at 1 min post exercise was not different from the pre-exercise value; however, by 5 min of recovery K+ content was significantly decreased and it remained decreased throughout the recovery period. It is concluded that there are very rapid and large fluid and electrolyte shifts between body compartments during and after high-intensity exercise, and that full recovery of these shifts requires 90–120 min.

The objective was to compare vitamin E content in the total diet of Arabian horses competing in the 80 km Research Ride 2002 to the oxidative stress and antioxidant measures throughout the race. Prior to the race, riders completed a detailed nutritional survey, which was used to calculate vitamin E intake. Blood samples, temperature and heart rate were taken the day before the race, at 27 and 48 km during the race, at race completion or elimination and 3 h after race completion. Plasma lipid hydroperoxides, α-tocopherol (TOC), creatine kinase (CK), aspartate aminotransferase (AST), albumin, red and white blood cell total glutathione and glutathione peroxidase were measured. Data were analyzed by Pearson's correlation in SAS. From the survey, it was estimated that horses consumed 2265±114 IU day−1 of vitamin E. A negative correlation was found between the vitamin E intake and CK (r = −0.23; P = 0.002), and AST (r = −0.22; P = 0.003). A positive correlation was found between the vitamin E intake and plasma TOC (r = 0.15; P = 0.005) at all sample times. This suggests that intensely exercising horses supplemented with vitamin E may not have an improved welfare and performance if they are supplemented vitamin E versus what is naturally found in forages and commercial feeds.

The purpose of the present study was to investigate the effect of adrenaline on cardiac function parameters. The infusion of adrenaline for induction of stress, its prospective side-effects as well as its effect on left ventricular function were investigated. A clinical examination and echocardiography were performed on 10 healthy horses before and after infusion of adrenaline. During a period of 6 min, infusion of 1 μg adrenaline kg−1 min−1 led to a significant increase in mean heart rate, from 36.5 to 55 beats min−1. Echocardiography during adrenaline infusion revealed a significant thickening of the interventricular septum (during systole) as well as a significant decrease in left ventricular diameter at the papillary muscle level (during both systole and diastole), and thus an increased contractility. The left ventricular area and the left ventricular volume were significantly decreased during adrenaline infusion, expressing the increased left ventricular contractility (during both systole and diastole). Other echocardiographic parameters of regional left ventricular function changed with only low-grade significance or without any significance at all. During and after infusion of adrenaline, the horses showed sweating, muscle tremor and other symptoms of discomfort. The study revealed that the increases in heart rate and myocardial contractility after infusion of adrenaline were low compared with changes observed during physical performance. Furthermore, severe adverse effects were observed. Taking into account the possible cardiotoxic effects of adrenaline, we do not consider this method appropriate for stress induction, particularly in horses with cardiac disorders.

This study tested our hypothesis that during an 80-km Research Ride in 2002 (R2) horses that did not finish (NF) the ride would have elevated muscle enzyme activities in the blood and changes in biomarkers of oxidative stress as compared to horses that finished (F) the ride. These results were then compared to previous rides – Old Dominion (OD) and the Research Ride 2001 (R1). For R2, 40 mostly Arabian horses competed and had blood samples collected before, at 27, 48 and 80 km, and 170 to 190 min after the 80-km race. Blood was collected similarly in R1 and OD. Blood was analysed for plasma lipid hydroperoxides (LPO), α-tocopherol (TOC), creatine kinase (CK), aspartate aminotransferase (AST), red and white blood cell total glutathione (GSH-T) and glutathione peroxidase (GPx). Data were analysed using a repeated measure ANOVA in SAS. Associations between muscle enzymes and antioxidant status were determined using Pearson's or Spearman's correlations. Activities of CK and AST were higher (P<0.05) before, during and after the ride in NF than in F; however, TOC, LPO, GSH-T and GPx were not different. In R2, negative correlations were found with GPx and CK (r = −0.21; P = 0.005), GPx and AST (r = −0.15; P = 0.05), and a positive correlation was found with GSH-T and CK (r = 0.18; P = 0.02). Values of CK, LPO, GPx and GSH-T were higher (P<0.05) in R2 than in R1 or OD. The overall comparison of 80-km endurance races suggests the importance of considering the horse's fitness, terrain, ambient conditions and calibre of race when interpreting results from markers of oxidative stress and muscle enzyme leakage.

To the authors' knowledge, the effect of hoof balance alteration on exercise capacity or performance has not been investigated. With the aim of evaluating the relationships between longitudinal front hoof balance and exercise capacity (lactate vs. speed relationship, run time and stride characteristics), two experiments were undertaken. In the first test the horses, left unshod, performed an incremental speed test in which parameters chosen to evaluate exercise capacity were related to hoof longitudinal balance. In the second part of the study the same group of horses had the length of the toe altered (decreased and increased) with the application of shoes, while the angle of the foot and the height of the foot from the ground remained the same. The relative change in exercise capacity due to the alteration of longitudinal balance was observed. In the unshod experiment, lactate level at the speed of 10 ms-1 (5.0±2.0 mmoll-1) was significantly associated with the angles DC° (angle described by the dorsal cortex with respect to the ground; 50.0±3.2°) and PC° (angle described by the palmar cortex with respect to the ground; 29.6 ± 2.9°), while run time (14.07 ± 1.44 min) was associated with breakover indices (Breakover index1 0.33±0.03; Breakover index2 0.30 ± 0.04 – all values mean ± standard deviation (SD)) (breakover indices were created to express the distance between the point of the toe and the point of the third phalanx relative to the length of the palmar cortex or relative to the distance between the point of the third phalanx and the centre of rotation of the distal interphalangeal joint). These associations have to be judged cautiously because the influence of hoof balance on exercise capacity could be biased by other physiological factors and because hoof balance parameters themselves could reflect the conformation of other anatomical structures far from the phalanges. The selective alteration of front hoof balance in the second part of the study produced a significant difference in blood lactate level only at 6 ms-1 (mean ± SD: La6?m?s-1 0.32 ± 0.39 mmoll-1), with this benefit in terms of lactate level being associated with an increase in stride length (mean ± SD: ΔSL6ms-1 0.01 ± 0.05 m; ΔSL10ms-1 0.112 ± 0.218 m). In conclusion, while higher exercise capacity seemed to be associated with lower DC°, PC° and breakover indices, decreasing the toe length without altering the foot angle was beneficial only in terms of lactate level at the speed of 6 ms-1 for horses with DC° greater than 45°; this benefit was accompanied by a slight lengthening of the stride at both 6 and 10 ms-1.

Pregnant mares are often removed from work during gestation. However, little is known about the effects of exercise on the pregnant mare and her foetus. In the present study, maternal and foetal heart rates were monitored by electrocardiography before and after exercise in four equine pregnancies (days 250–285). Exercise consisted of lungeing mares in 20 m circles for 5, 10 and 20 min. Following exercise, significant increases in maternal heart rate were detected (P<0.0001) but not in foetal heart rate (P = 0.4331). All mares gave birth to normal foals uneventfully. While these findings suggest that moderate exercise of the pregnant mare does not appear to be harmful to the equine foetus, data are insufficient to draw conclusions. A larger, more controlled study is necessary.

The resistance of a track surface to deformation is known to be positively related to the magnitude of foot impact experienced during locomotion. Although passive mechanics suggests that this might be entirely due to the action of the track surface material decelerating the foot, it is also possible that the dynamics of locomotion are altered in a way that changes the landing velocity of the foot. The observed relationship between track properties and foot impact would then be due to a combination of the direct effect of the surface material and altered foot kinematics at impact. In this study we measured hoof landing velocity, stance time and limb landing angle in horses trotting over surfaces that differed significantly in their deformability. In comparison with a surface that underwent negligible deformation during stance phase, a surface that deformed 25 mm led to significantly increased stance time, significantly greater leg landing angle and significantly greater hoof landing velocity. Although the increased hoof landing velocity would act to counteract the increased shock absorption on the softer surface, we suggest that this effect is relatively small.

The present study used the physicochemical approach to characterize the changes in plasma electrolyte and acid–base states that occur in horses in response to feeding. Jugular venous blood was sampled every 0.5–2 h over a 24-h period from two groups (n = 4 and n = 5) of Standardbreds fed a mixed hay and grain ration at 8 am and 7 pm. One group of horses was studied in October, and one in December. The time course and magnitude of feeding responses differed between groups, and between the morning and evening meals. Feeding-induced changes in plasma electrolyte and acid–base variables occurred rapidly, within the first 1–3 h of meal consumption. The plasma acidosis associated with eating the meal was marked by increased plasma [H+] and decreased TCO2. The primary contributors to the increases in plasma [H+] were the decrease in the plasma concentration of strong ions ([SID]) and the pCO2. The increase in plasma total weak acid (protein) concentration ([Atot]) post-feeding had only a minor effect on the acid–base state. The feeding-induced acidosis abated 3–6 h after the meal, showing cyclical recovery of physicochemical variables that contributed to the acid–base disturbance. It is concluded that several key plasma electrolyte and acid–base parameters undergo significant, cyclical fluctuations in response to feeding in horses.

Because athletic horses become hypoxaemic and hypercapnoeic during high-intensity exercise but ponies do not, six Thoroughbred horses and five ponies performed an incremental exercise test at speeds with calculated energy requirements that were 40, 60, 80 and 115% of V˙O2max, with the objective of comparing their blood gas and ventilatory responses to exercise. Expired gas and blood samples were taken and breathing mechanics were assessed before exercise and during the last 15 s at each intensity. Maximal V˙O2 and V˙CO2 in horses were 153±5 (SEM) and 187±4 ml kg−1 min−1, respectively, while corresponding values in ponies were 92±4 and 112±7 ml kg−1 min−1. During heavy and supramaximal exercise, horses, but not ponies, became hypoxaemic and hypercapnic. There was no significant difference for V˙E kg−1 between groups during maximal exercise, but PAO2, PaO2 and PvO2 were lower and PaCO2 and [(A−a)O2D] were greater in horses than in ponies. Additionally, the horses' maximal transpulmonary pressure difference was higher and their total pulmonary resistance and ventilatory equivalent lower than in ponies. Flow-volume loops suggested that horses experienced expiratory flow limitation but that ponies did not. These results indicated that horses like Thoroughbreds appear to be expiratory flow-limited and become hypoxaemic and hypercapnic when the demand for gas exchange associated with their high V˙O2max and V˙CO2max is greater than can be met by their ventilatory system. Ponies, which are less capable athletes, could better match their ventilatory response with their metabolic capabilities and so were able to maintain PaO2 in the pre-exercise range and decrease PaCO2 to a tension that was more compatible with acid–base homeostasis.

Subjective bias by judges within the dressage phase of eventing competition is problematic if correct evaluation of horse and rider performance is to be undertaken. The present study examines dressage penalty scoring (penalty scores are awarded for completion of a pre-set series of dressage movements) within a population of novice event horses (n = 2471). Between May and June 2003, 22 novice events within the UK were analysed, and at each event up to six competitions or sections (at the same competitive level) were run. The whole population data structure was normal in distribution, Pearson's skewness 0.314 (Kolmogorov–Smirnov Z = 1.855, P>0.05 from zero) and kurtosis at 0.425. The mean score recorded for the whole population was 37.82 penalty points (standard deviation = 5.65 and standard error = 0.11). A number of effects were observed within the population. Between-events effects were observed in three of the 22 events studied (P<0.01). Of those events running three or more sections (n = 16), within-event effects were observed for 10 events as differences (P<0.01) in mean scoring patterns between sections. All events running two sections (n = 4) were observed to exhibit differences (P<0.02) in mean scores. Differences (P>0.01) between the dressage test used at events were determined using post hoc Bonferroni tests. However, these differences were not found to have a confounding effect on the between-event observations. The study indicates that additional methodologies need to be implemented to ensure that accurate and impartial evaluation of event horses is conducted.

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.

It has been suggested that the presence of a bit reflexly increases salivation but, at the same time, interferes with the horse's ability to swallow. The objective of this study was to compare swallowing frequency in 12 horses exercising at canter while wearing a head collar, a bitless bridle, a jointed snaffle bit and a Myler correctional-ported barrel bit. Laryngeal movements were recorded videoendoscopically as the horses cantered (8 m s−1) on a high speed treadmill, with the use of side reins to flex the poll. Swallowing was stimulated artificially by infusion of sterile water at a constant rate of 5 ml min−1 through a cannula in the endoscope's biopsy port. The results showed large differences in swallowing frequency between horses. Swallowing frequency was lower for the Myler snaffle than for the other conditions (P<0.05). It is concluded that the presence of a bit does not preclude swallowing during exercise at canter with the poll in a flexed position, but certain types of bits may be associated with a reduction in swallowing frequency.

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.

A preliminary investigation into the structure of the competing sport horse population within the UK for the year 2000 was undertaken, comprising 30 974 horses and 39 679 individual performances. All performance data were expressed as total lifetime winnings. The level of non-winning horses, expressed as a percentage, was high in all disciplines: dressage 22%, eventing 50% and show jumping 23%. The percentage of horses competing in disciplines at the highest recognized level was small: dressage 2.5%, eventing 10% and show jumping 6.5%. Highest earners for all disciplines all earned considerably more than the threshold for highest performance level in their respective discipline (×2.2 dressage, ×24 eventing, ×365 show jumping). Data for all three disciplines were highly skewed. Structural analysis of the distributions by level showed a highly skewed hypogeometric distribution at the lowest level of competition for all disciplines, uniform distribution at intermediate levels (bimodal tendencies were observed within dressage) and normal distribution at advanced levels. Product–moment correlations showed a significant correlation between show jumping and eventing (0.228, P<0.01). Problems with data availability and presentation may mean that up to 12.9% of the population may have had a confounding effect on the results of this study.