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).

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.

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 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.

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.

Sustained strenuous exercise has been shown to produce gastrointestinal disease in athletic species, but the causative factors remain unknown. Since exercise results in oxidative stress and hypercortisolaemia, we tested the hypothesis that oxidative and physiological stress cause gastrointestinal disease in racing Alaskan sled dogs. Dogs from three racing teams were examined before (pre) and immediately after (post) completing a 1770-km sled dog race in approximately 11 days. Serum cortisol and isoprostane concentrations were compared with markers of gastrointestinal barrier integrity and endoscopic evidence of gastric ulceration. Gastric barrier integrity was assessed by measuring the urinary recovery of sucrose and intestinal barrier integrity was assessed using the urinary recovery ratio of lactulose to rhamnose (L/R), administered together by orogastric gavage. Exercise produced a significant increase in median serum cortisol (pre: 1040, 717–2946 pg ml−1 (range); post: 8072, 2228–29 571 pg ml−1; P<0.0001) and L/R recovery ratio (pre: 0.110, 0.060–0.270; post: 0.165, 0.080–0.240; P=0.009) but not isoprostane (pre: 1007, 656–2305 pg ml−1; post: 1164, 23–4710 pg ml−1; P=0.194) concentration. The increased serum cortisol concentration was not correlated with a change in L/R recovery ratio or urine sucrose concentration. Dogs with abnormal gastric endoscopy results (61% of finishers) had higher serum cortisol concentrations than dogs with normal endoscopy results (P=0.0007). We have demonstrated concurrent hypercortisolaemia and gastrointestinal barrier dysfunction with no correlation of the two. Thus, our data do not provide support for the hypothesis that increased serum cortisol concentration causes exercise-induced gastrointestinal disease.

Despite the increasing use of lasers in the rehabilitation of horses, the biophysical action of the laser is not clearly defined. The purpose of this study was to determine the effect of a defocused CO2 laser on the temperature of the skin, subcutis and fetlock joint in standing and anaesthetized horses. A cross-over design comprising 10 standing horses was used. Consecutive irradiation (91 J cm−2) was applied to each of the three aspects of the front fetlock joint of these animals. In 12 anaesthetized horses (eight laser-treated and four control), irradiation (137 J cm−1) was applied to the dorsal side of the joint. In the standing group, skin temperature increased on average by 5.3°C to 34.8±1.5° (P<0.05) and the subcutis temperature increased by 5.7°C to a mean temperature of 36.0±0.9°C during laser treatment. There was no difference in joint temperature between laser-treated and control horses. Similar results were obtained in anaesthetized horses. Treatment with a defocused CO2 laser caused a significant increase in the temperature of the skin and subcutis, but not in the joint cavity. Further studies are needed to investigate if the increase in temperature influences perfusion and modulation of pain, as a result of defocused CO2 laser treatment.