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.

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.

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.

Chromium (Cr) is required for insulin function in the control of cellular glucose uptake. Other functions of Cr relate to its effects on growth, lipid metabolism, immune responses and interactions with nucleic acids. This study was conducted to obtain information on the effect of Cr supplementation on the metabolic responses of five exercising Standardbred horses. During the experiment, horses were fed every day for a 21-day period in a randomized order either a yeast product without Cr (control) or with 4.15 or 8.3 mg Cr day−1. Horses were exercised on a treadmill, alternating a work day of low-speed exercise at 5 m s−1 on a 3% incline for 45 min with a rest day. Each horse was adapted over a 21-day period to his or her respective supplementation before undergoing a standardized exercise test (SET). The SET comprised five incremental steps, each of 4 min duration, on a treadmill with a 3% incline; the first step was at 5 m s−1 and was followed with increments of 1 m s−1. Blood samples were taken for lactate, plasma glucose, serum insulin and cortisol estimation before, during and after each SET (30, 120 min and 24 h post-exercise). Blood Cr was estimated 2 h after feeding the control or Cr-enriched yeast (intake 8.3 mg Cr) in two horses. Heart rate was monitored throughout each SET. Blood lactate and plasma glucose peaks were highest at 8 and 9 m s−1 during the SET when 8.3 mg Cr was supplied. Serum insulin levels declined during the SET and there were no treatment-related changes. Twenty-four hours after exercise, plasma glucose and serum cortisol concentrations returned to basal levels or lower. Serum insulin rebounded 30 min after exercise but 24 h later, serum insulin concentrations were below resting levels. During the recovery period, Cr supplementation did not clearly affect metabolic responses. These results suggest that Cr supplementation had no beneficial effect in healthy, exercising horses.

Five male ponies (3–6 years, 208±11 kg) were used to examine the haemodynamic effects of resistance exercise. The experiment consisted of a 30 min catheterization period and a 15 min equilibration period followed by the test. Initially, the ponies stood quietly on a treadmill for collection of 5 min of baseline data. They then walked at 1.9 m s−1 for 1 min sets while carrying 0 kg, 67 kg or 134 kg of weight loaded on the saddle area. Weights were applied in a randomized order using a chain hoist and sling. The ponies rested unloaded for 2 min between sets and all cardiovascular parameters returned to baseline before beginning the next set. Haemodynamic measurements (heart rate (HR), carotid artery systolic (SP), diastolic (DP), pulse (PP) and mean pressure (MAP), right atrial pressure (RAP), right ventricular pressure (RVP) and right ventricular maximum rate of pressure rise (dP/dtmax)) were recorded continuously and data collected during the last 18 s of each set were averaged and analysed. HR increased (P<0.05) with unloaded exercise (201%) and with increases in load (252 and 271% at 67 and 134 kg, respectively). RAP increased (P<0.05) with exercise, with differences (P<0.05) between the response to the 0 kg (66%), 67 kg (121%) and 134 kg (138%) loads. RVP increased (P<0.05) incrementally with load during exercise (58, 110 and 136%, respectively), with differences (P<0.05) between 0 versus 67 kg and 67 versus 134 kg. Right ventricular dP/dtmax increased (P<0.05) incrementally and showed differences (P<0.05) between loads (131, 191 and 252% at 0, 67 and 134 kg, respectively). There were increases (P<0.05) in MAP (20%), SP (20%) and DP (27) with exercise, but no difference (P>0.05) between the response to 67 versus 134 kg load (43 and 51%; 40 and 46%; 49 and 62, respectively). Pulse pressure did not change (P>0.05) from baseline values. These data suggest that resistance exercise in the form of weight carried increases intraventricular pressure through a significant increase in both cardiac pre-load and after-load.

Training and competing at elite as well as sub-elite level requires an optimal functioning of the body. This review looks at the case of the Kenyan runners, who consume a relatively high-quality diet based on vegetable sources with maize and kidney beans as the staple foods. The diet is high in carbohydrate and total protein, but low to borderline in a few essential amino acids. The timing of diet intake – immediately after training sessions – is optimal for skeletal muscle glycogen resynthesis that is enhanced without the help of insulin up to 60 min after cessation of exercise. Whether the total energy intake of the Kenyan runners is adequate is debatable. However, chronic undernutrition is not possible for athletes who engage in daily high-quality and -quantity physical exercise throughout most of the year. It is suggested that Kenyan runners participate in well-controlled, laboratory studies to investigate the quality of local foods and performance, as well as possible physiological adaptation mechanisms among athletes with a high habitual energy turnover.

A prospective, blinded, randomized and controlled study was conducted in horses with traumatic arthritis of the metacarpophalangeal joint in order to evaluate the efficacy of defocused carbon dioxide (CO2) laser therapy. Sixteen horses were randomly assigned to two groups: active laser (an output power of 16 W, scanned over 42 cm2, an average dose of 91 J cm− 2) and sham laser (the laser beam directed at the non-reflecting floor). All the horses received a total of five treatments during 1 week. The horses were evaluated with respect to the degree of initial lameness by conventional lameness examination and an objective accelerometer technique before the onset of treatment, and at 1 and 3 weeks. The concentrations of substance P (SP), prostaglandin E2 (PGE2) and Met-enkephalin-Arg-Phe (MEAP) in synovial fluid were also assessed. Our study demonstrates that there was no significant difference in lameness score between the laser- and the sham-treated group before the treatment and at 1 and 3 weeks after the initial examination. Moreover, no significant difference in the concentrations of SP, PGE2 and MEAP in synovial fluid in the active laser group compared with the sham-treated group was observed. In conclusion, this study suggests that treatment with defocused CO2 laser in the management of traumatic arthritis of the metacarpophalangeal joint is not statistically better than sham treatment at reducing the grade of lameness as evaluated by conventional lameness examination and accelerometer technique.

The objective of this study was to determine the relationship between insulin sensitivity and aerobic capacity and serum adipocytokine (leptin, adiponectin) concentrations in 14 mature, unconditioned Standardbred horses (eight mares, six geldings). Each horse underwent a euglycaemic–hyperinsulinaemic clamp (EHC) and a frequently sampled intravenous glucose tolerance test (FSIGT) for assessment of insulin sensitivity. Aerobic capacity was determined by measurement of the peak rate of oxygen uptake (V˙O2peak) during an incremental exercise test (IET). Serum leptin and adiponectin concentrations were measured in baseline samples obtained before tests of insulin sensitivity. Mean body weight, condition score, V˙O2peak and run time during the IET did not differ between the sex groups. However, minimal model analysis of the FSIGT showed that insulin sensitivity (SI, ×10−4 l mU−1 min−1) was higher (P = 0.002) in geldings (4.21±0.78) than in mares (2.43±0.95), while the acute insulin response to glucose (AIRg) and glucose utilization independent of insulin (SG) were significantly higher in mares. Similarly, glucose uptake (M) per unit of serum insulin (I) during the EHC (M/I ratio) tended (P = 0.08) to be higher in geldings than in mares (×10−2 mg kg−1 min−1 per μU ml−1: 2.41±0.64 vs. 1.80±0.51). There was no significant relationship between V˙O2peak and measures of insulin sensitivity. Stepwise multiple linear regression modelling determined that sex (65%) and leptin concentrations (13.7%) accounted for 78.7% of the variance in SI, while 46% of the variance in M/I could be attributed to sex. It was concluded that aerobic capacity is not an important determinant of insulin-mediated glucose disposal in mature, untrained Standardbred horses. Further studies are needed to examine the influence of gender on insulin sensitivity in horses.

Silicon appears to be an essential element for proper endochondral ossification and glycosaminoglycan synthesis. Osteochondrosis (OC) is characterized by disturbed endochondral ossification, and glycosaminoglycan loss has been reported in OC lesions. Therefore, silicon may be effective in reducing OC lesions. The objective of the study was to evaluate the effects of supplemental silicon on OC lesion size. Initial radiographs were taken on 2-year-old Standardbreds (n = 44) on private facilities to identify OC defects in the distal third metacarpus/tarsus or osteochondral fragments at the dorsal aspect of the joint and defects/fragments at the distal tibia and on the trochlear ridges of the talus. Only clinically sound horses were included. Follow-up radiographs were taken at 120 days. Radiographs were digitized and the length and height of the OC defects/fragments were measured. Horses meeting study-inclusion requirements (n = 8) were pair-matched by facility and affected joint(s) and assigned to a group: control (receiving 200 g whole grain flour) and silicon supplemented (receiving 200 g bioavailable silicon source). Treatments were top-dressed on the feed for 120 days. Due to the onset of lameness, four horses did not complete the 120-day study duration. There was no effect (P>0.22) of treatment, time or treatment × time on lesion length, height or area. Silicon supplementation did not alter the radiographic appearance of OC lesions. Future research should focus on the effects of a silicon supplement on the prevention of OC lesions.

Despite the high athletic demands of Greyhound racing and recommendations for the inclusion of pre-race warm-up by some veterinarians, the extent of warm-up practices by Greyhound owners and trainers remains unexplored. We postulated that little pre-race warm-up occurred and any warm-up activities were performed at random. A cross-sectional study design was used to examine pre-race warm-up practices in a sample of 80 Greyhounds. Warm-up components were recorded and scores were assigned in order to quantify the total amount of warm-up undertaken. Associations between total warm-up and signalment and race characteristics were analysed statistically. Correlations between total warm-up performed and all variables including race distance, race order, grade of Greyhound and trainer were poor (all r < 0.2). No statistically significant association between total warm-up and any variable examined could be demonstrated at the P = 0.05 level, although a weak trend towards graded Greyhounds performing more warm-up was noted (P = 0.09). We conclude that little pre-race warm-up is performed in Greyhounds and that when practised, the amount and methods of warm-up are inconsistently applied.

Our objective was to determine if feeding a high-fat supplement versus a control supplement to growing yearling mares would affect growth an/r body composition parameters as assessed via body weight (BW), body condition scores (BCS) and concentrations of plasma hormones. Eight yearling mares were paired by initial BW (348±19kg) and maintained on pasture and supplemented with either a high-fat supplement (16% fat) or a control supplement (3% fat) at 0.8% of their BW in two daily meals for 8 weeks. Both BW and BCS increased for all mares throughout the study (each P<0.0001); however, no difference in BW or BCS could be attributed to treatment effects. Nonetheless, plasma concentrations of leptin were greater in mares fed the high-fat supplement (P = 0.0001) compared with the control supplement. Plasma concentrations of growth hormone tended to be greater in high-fat-fed mares (P = 0.06). Plasma concentrations of insulin did not differ between treatment groups (P = 0.96). Although no gross difference in BW or BCS was discernable among mares fed the control versus high-fat supplement, these data provide evidence that increasing fat content in the diet may alter leptin levels independent of changes in body composition.

The role of cardiac function or dysfunction in the pathogenesis of exercise-induced pulmonary hypertension and haemorrhage in horses has been minimally investigated. We hypothesize that pericardiotomy would enhance diastolic function and attenuate pulmonary vascular pressures in maximally exercising horses. Our objective was to evaluate diastolic function and cardiopulmonary pressures before and after pericardiotomy, at rest and at maximal exercise. Study design was both self- and externally controlled. Five horses underwent pericardiotomy after a baseline exercise test. They subsequently performed the same exercise protocol at 1 week and 13 weeks post-operatively. An external, unoperated control group of five horses performed the same experimental protocol. Pulmonary arterial pressure (PAP), pulmonary artery wedge pressure (PWP), right ventricular pressure, heart rate (HR) and oesophageal pressure were measured continuously at rest and at maximal exercise; maximum rates of ventricular pressure decrease (−dP/dtmax), relaxation half-time (t1/2), time constant of isovolumic relaxation (τ) and pulmonary capillary pressures (PcapP) were derived. Statistical analysis was performed using two-tailed Wilcoxon's signed-rank and rank-sum tests, with significance set at P<0.05. No significant differences were found in any variable after pericardiotomy was performed or between the experimental and external control groups. We conclude that during a 13-week study period, pericardiotomy does not alter pulmonary or ventricular pressures or rate of ventricular relaxation in the resting or maximally exercising horse. Results indicate that, in past and future studies requiring an open pericardium in normal horses, the cardiopulmonary parameters measured here are not affected by reduced pericardial pressure.

The interactions between nutrition, energy status and acid–base balance during exercise are poorly understood. Exercise, under conditions of prior glycogen depletion (GD) and low-carbohydrate diet, results in a decreased rate of skeletal muscle glycogenolysis, greatly decreased muscle pyruvate and lactate contents with decreased plasma [lactate] (Putman et al., Am J Physiol, 265: E752, 1993). Therefore, it is hypothesized that exercise in GD, compared with normal (NG) or high-carbohydrate conditions, will result in a reduced magnitude of acidosis due to reduced production and accumulation of lactate. In two trials (GD, then NG) separated by 1–2 weeks, four men cycled at 75% of peak VO2 until the time of exhaustion in GD (57 ± 7 min). At 2 min of exercise, femoral vein (fv) plasma [H+] was increased by 21 ± 4 neq l− 1 (NG) and 14 ± 3 neq l− 1 (GD); increases in arterial [H+] were only c. 45% of those in fv plasma. The increase in fv PCO2 (NG, 25 ± 2 mm Hg and GD, 15 ± 2 mm Hg) was the primary variable responsible for the increased [H+]. During NG, the increase in fv [lactate− ] exceeded the decrease in strong ion difference [SID], with electrolyte charge balance mainly due to increased [Na+]. In the GD trial, arterial [SID] decreased and was the primary contributor to the increased [H+], as passage of blood through the lungs eliminated the CO2 contribution prevalent in fv plasma. Throughout GD, plasma [lactate− ] increased less than in NG and the decrease in [SID] in GD was also significantly less than in NG. In summary, in GD conditions, an attenuated production/release of lactate−  and CO2 from muscle resulted in reduced magnitude and duration of acidosis compared with NG conditions. In fv plasma, increased PCO2 was the primary variable responsible for the rapid and sustained elevation in [H+], whereas in arterial plasma decreased [SID], due to increased [lactate− ], was primarily responsible for increased [H+].

Repeated strenuous exercise while breathing cold air is believed to induce chronic airway inflammation and hyperreactivity, a condition referred to in humans as ‘ski asthma’. However, the time course of development and resolution of ski asthma is unknown. We have previously shown that multi-day aerobic exercise induces airway inflammation and hyperreactivity in racing sled dogs. In the present study, a similar group of subjects was examined at multiple times during training to test the hypothesis that ski asthma spontaneously resolves during seasonal detraining, but is re-induced during training in the cold weather. At the beginning of training, bronchoalveolar lavage fluid (BALF) from detrained elite sled dogs (n = 16) had higher concentrations of lymphocytes (median 53.63 vs. 8.30 cells μl−1) and neutrophils (median 23.03 vs. 1.10 cells μl−1) compared with normal laboratory dogs (n = 5). However, there was no significant effect of training on BALF nucleated cell concentrations from exercised sled dogs (n = 11) compared with sedentary sled dogs (n = 8). In contrast to our hypothesis, our data support the contention that cold weather exercise-induced airway inflammation can persist through seasonal detraining, but that routine training does not cause significant worsening of the condition.

We studied the extent to which intra-articular hyaluronic acid (HA) administered to horses with experimentally induced synovitis in the third middle carpal joint altered cartilage proteoglycans (PGs) and the biomechanical properties of the third carpal bone. Intra-articular HA (Hylartin-V®) was administered to the middle carpal joints of healthy horses before and after the induction of synovitis by Escherichia coli lipopolysaccharide (LPS). Two groups of horses received intra-articular HA only, with evaluation 2 and 6 weeks later (group 2 and group 4). Two other groups (group 1 and group 3) received LPS followed by intra-articular HA and evaluation 2 and 6 weeks later. Ex vivo third carpal bone cartilage PG synthesis was measured by 35SO4 incorporation and third carpal bone cartilage PG content was determined by an assay for glucuronic acid. Biomechanical properties were measured by indentation testing. At the 2-week evaluation, HA did not ablate the quantitative reduction in PG synthesis and PG content in animals with experimental synovitis. However, by 6 weeks, there was a significant rebound effect in that PG synthesis and PG content were elevated in horses with experimental synovitis that had received intra-articular HA, compared with horses that had received HA only for that period of time. There were also alterations in the gel filtration profiles of newly synthesized PGs on Sepharose CL-2B among the groups. However, there were no de novo PG species associated with any of the treatments. Furthermore, we found that the biomechanical properties of third carpal bone cartilage were not altered in any of the groups. These studies showed that intra-articular HA administered to horses with experimentally induced synovitis did not provide short-term (i.e. 2-week) benefit to third carpal bone cartilage PG synthesis. However, a long-term benefit of intra-articular HA may occur after the acute effects of synovitis on PG synthesis and PG content subside.

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).

Several studies have shown that the placement of a face mask on a horse can have effects on ventilation, gas exchange and the cardiovascular system during exercise. The aim of the present study was to determine if airflow and ventilation measured with the same ultrasonic flowmeters were different during exercise between horses wearing half- (HM) and full-face (FM) masks. Five clinically healthy Thoroughbred horses with no history of respiratory disease were studied in an unbalanced crossover design. They were exercised on a treadmill at speeds between 1.7 and 11ms−1 on a 3° incline wearing both masks. The following variables were recorded: peak inspired (PIF) and peak expired flow rates (PEF), inspiratory tidal volume (VT), respiratory rate (fR ), inspiratory minute ventilation (VE), inspiratory time, (TI), expiratory time (TE ), total breath time (TT), end tidal oxygen (ETO2), end tidal carbon dioxide (ETCO2) and heart rate (HR). A mask by speed of exercise interaction term was not significant for any of the models. The PEF (mean difference 12.91s−1; lower and upper 95% CI 7.6 and 18.21s−1, respectively; P<0.0001) and ETO2 (mean difference 0.77%; lower and upper 95% CI 0.48 and 1.00%, respectively; P<0.0001) were significantly greater and ETCO2 was significantly lower (mean difference −1.3%; lower and upper 95% CI −2.0 and 0.7%, respectively; P<0.0001) with the FM compared with the HM. There was also a trend for inspired VE to be higher with the FM compared with the HM (mean difference 1021min−1; lower and upper 95% CI 26 and 1781 min−1, respectively; non-significant). We conclude that the HM may impair ventilation in the horse during exercise compared with the FM, despite the latter having a greater deadspace.

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.