An optimally functional musculoskeletal system is crucial for athletic performance and even minor perturbations can limit athletic ability. The introduction of the muscle biopsy technique in the 1970s created a window of opportunity to examine the form and function of equine skeletal muscle. Muscle histochemical and biochemical analyses have allowed characterization of the properties of equine muscle fibres and their influence on, and adaptation to, physical exertion. Analyses of exercise responses during standardized treadmill exercise and field studies have illustrated the role of cellular energetics in determining athletic suitability for specific disciplines, mechanisms of fatigue, adaptations to training and the affect of diet on metabolic responses. This article provides a review of the tools available to study muscle energetics in the horse, discusses the muscular metabolic pathways and summarizes the energetics of exercise.

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.

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+].

At any level of competition, men run faster than women. Consequently, a male speed advantage is often presumed for other species. This assumption was tested in two animals bred for speed: horses and dogs. Results from Thoroughbred (TB), Standardbred (STB) and Greyhound (GH) races were analysed by ANOVA to compare the speeds of victorious males, neutered males (TB and STB only) and females. Separate analyses were run for shorter (TB: ≤ 1609 m, GH: 503 m) and longer (TB: >1609 m, GH: 603.5 m) TB and GH races. All STB races (trotters and pacers) were 1609 m. In TB races, intact males were 0.7% faster than females at ≤ 1609 m (n = 305; P < 0.01) and 1.4% faster at >1609 m (n = 194; P < 0.01). The speed of neutered males was equivalent to that of females at both distances. Gender accounted for 3.8 and 10.7% of the variance in speed at short and long distances, respectively. In STB pacers, intact males were 1.5% faster than females and gender accounted for 10.1% of the variance in speed (n = 96; P < 0.01). Gender was not a significant predictor of STB trotter (n = 95) or GH speed at 503 m (n = 146) or 603.5 m (n = 23). In conclusion, gender has a significant effect on speed of TBs and STB pacers. Although the effect size is small, it may be significant for racing; in a 7 furlong (1408 m) TB race, the 0.7% difference translates to an advantage of several lengths.

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.

The present study used the physicochemical approach to characterize the changes in acid–base status that occur in Standardbreds after post-exercise electrolyte supplementation. Jugular venous blood was sampled from six conditioned Standardbreds on two separate occasions, at rest and for 24 h following a competitive exercise test (CET) designed to simulate the speed and endurance test of a 3-day event. After the CETs, horses were given water ad libitum and either a hypotonic commercial electrolyte solution, via nasogastric tube followed by a typical hay/grain meal, or a hay/grain meal alone. The electrolyte supplementation resulted in c. 2 mmol l− 1 decreased plasma [TCO2] during the recovery period as compared with control. The primary contributor to the decreased [TCO2] with electrolyte supplementation was a decreased strong ion difference ([SID]), as a result of the non-significant increase in plasma [Cl− ]. Additionally, electrolyte supplementation resulted in faster restoration of hydration status compared with control, as evidenced by faster recovery of plasma [protein] and total weak acid concentration ([Atot]). It is concluded that oral administration of a hypotonic electrolyte solution after prolonged moderate-intensity exercise diminishes the post-exercise alkalosis, and that recovery of hydration status is still incomplete 24 h after exercise when no electrolytes are given. Thus, supplementation with electrolytes according to estimated sweat losses may attenuate post-exercise increases in plasma [TCO2], which is of significant practical interest to the horse racing community, as a testing threshold of greater than 37 mmol l− 1 is used by many racing jurisdictions to determine whether a horse has been administered an alkalinizing agent.

The aim of this study was to identify the effect of training stage, height of the obstacle and successive number of jump on young stallions' linear jumping parameters with and without rider. Investigations were based on filming of free jumping and jumping with rider during regular stallion work on the 11-month performance test. Horses jumped through the spread obstacle (doublebarre) with constant width of 90 cm and heights of 100, 110 and 120 cm. Taking-off distance, landing distance, heights of legs above obstacle and bascule of horse silhouette were measured using manual programme for video image analysis. Almost all parameters measured with and without rider were training dependent. The only parameters not affected by training were heights of hind limbs above obstacle, which were also not affected by height of obstacle in observations of more trained horses by free jumping and less trained horses with rider. Jumping parameters were not influenced by successive number of the jump by all parameters with rider and parameters of length of the jump in free jumping. On the basis of received results, it could be concluded that evaluation of jumping skills in free jumping and jumping with rider should be based on different criteria.