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).

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.

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.

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.

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.

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.

The objective was to describe and compare the positions of different types of bits within the horse's oral cavity. Eight horses were fitted with a bridle and six bits [jointed snaffle ( JS), Boucher, KK Ultra, Myler snaffle (MylerS), Myler ported barrel (MylerPB), Myler correctional-ported barrel (MylerCPB)]. Lateral radiographs and custom software were used to measure the position and orientation of the bits relative to the horse's palate and second premolar teeth without rein tension and with 25±5 N bilateral rein tension. The results showed differences in the position of the bits within the horse's oral cavity and in their movements in response to rein tension. Without rein tension, single-jointed bits were further from the premolar teeth ( JS 32.2±10.6 mm; Boucher 33.9±10.8 mm) than the Myler bits (MylerS 20.2±9.7 mm; MylerPB 12.8±6.7 mm; MylerCPB 14.6±4.3 mm). Single-jointed bits moved closer to the premolars when tension was applied to the reins (JS 20.8±6.3 mm; Boucher 19.7±6.8 mm). The cannons of the Boucher were more elevated than those of the other bits. The cannon angulation decreased significantly from 38.7±13.7 deg. to 21.6±6.9 deg. for JS and from 43.1±10.1 deg. to 27.8±10.1 deg. for the Boucher when tension was applied to the reins. The Myler bits showed minimal change in position in response to the application of rein tension.

A pilot study was performed using a strain gauge transducer intercalated between the bit and the left rein to measure rein tension dynamically during riding. The strain patterns consisted of a series of spikes with frequencies corresponding to two per stride in walk and trot and one per stride in canter. The highest tension recorded in each gait was 43 N at walk, 51 N at trot and 104 N in canter. Based on the results of this study, it is recommended that the methodology should be adapted so that both reins are instrumented simultaneously, data are transmitted telemetrically to eliminate the need for a tether connecting the horse to the computer, and kinematic data are synchronized with the rein tension recordings.