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.

At the International Conference on Equine Exercise Physiology (ICEEP7), about 70 people attended the workshop on workload and conditioning guided by the authors. Most of the audience were involved in Thoroughbred or Standardbred racing, and only a limited number of people were mainly involved in FEI equestrian disciplines (sport horses). The workshop and this review article address the measurement of workload and conditioning of the Thoroughbred racehorse. It was proposed that workload could be quantified using a few selected parameters commonly recorded in the racing industries, such as velocity and distance, to generate a cumulative workload index. The review of conditioning focuses on the Thoroughbred racehorse and examines what can be modified with training, how training programmes should be designed based upon scientific methods and how training programmes should be routinely designed in current practice. It would appear that, in general, the methods used in practice for training Thoroughbred racehorses are quite similar to those used in a set of recent scientific studies, particularly in young (2–3-years-old) Thoroughbreds. Nevertheless, both the length of the training programme and the total amount of exercise are usually shorter/lower than ideal in order to maximize physiological adaptations within the animal's body. In planning the training programme, it is very important to recognize that different adaptations occur at different rates, and this will affect the relative amount of training that should be applied to achieve specific adaptations.

Kinematic analysis has been used to understand performance in many sports, but few objective studies of equestrian technique have been published. The objective was to describe movements of the rider's torso and arms relative to movements of the horse's pelvis and shoulder and the position of the bit during trotting. Six experienced female riders rode the same dressage horse at a sitting trot, with rider and horse kinematics collected. The trot is a symmetrical gait, which implies kinematic symmetry between the first and the second halves of the gait. Three trials of a half stride, from left forelimb lift-off to right forelimb lift-off, were analysed for each subject. In all riders, trunk angle was maximal (backward tilt) in early stance, at which time the rider's hips were closest to and the rider's shoulders were furthest from the bit. Trunk angle was minimal (forward tilt) at the end of stance when the shoulders were closest to and the hips were furthest from the bit. Range of motion of the rider's hips and shoulders varied greatly between subjects. Movements of the rider's shoulder joint and elbow joint were synchronized with the trunk oscillations, so the distance from the rider's wrist to the horse's bit changed by only 15 ± 3 mm during the stride. It is concluded that the six experienced riders were able to accommodate the motion of the horse's body while maintaining a consistent contact with the bit by minimizing changes in the distance from the wrist to the bit.

Pain, atrophy and dysfunction of the longissimus dorsi in the equine back can lead to poor performance and altered biomechanics. Back problems are often treated by manipulative therapy to this muscle. The purpose of this study was to identify if manipulative therapy resulted in changes to muscle tone or electromyographic (EMG) activity immediately after treatment. We measured the muscle tone during standing using a mechanical tissue indenter and the EMG activity (both at the T16 level in the longissimus dorsi) during walking around a figure-of-eight course in 26 horses. The horses were randomly assigned into three groups that received: (a) spinal (McTimoney) manipulations, (b) reflex inhibition therapy or (c) a control group that was not manipulated. The muscle tone and activity were measured immediately after treatment. Both the McTimoney and the reflex inhibition groups showed significant decreases in muscle tone (c. 12%) and walking EMG activity (c. 19%). The control group showed no significant change in tone or EMG activity. These results document how the longissimus dorsi muscle responds immediately after manipulative therapy. Further studies would be needed to identify how long such changes persist or if such changes caused a reduction in pain or an increase in performance.

This brief review examines the athletic potential of mammals in general and the horse in particular as it relates to oxygen (O2) transport and utilization. The horse has been bred selectively for over six millennia based upon its ability to run fast. Whereas this has optimized cardiovascular and muscle function and the capacity to deliver and utilize O2, it has resulted in lung failure during intense exercise. Horses in their athletic prime are considered and attention is focused on their maximal capacities as related to O2 transport, irrespective of age per se. Following a few comments on the history of O2, this review moves from established principles of O2 transport at the integrative organ level to the microcirculation and the processes and principles that govern O2 offloading, where much remains to be discovered. Four principal questions are addressed: (1) as an athlete, what are the most outstanding physiological characteristics of the horse? (2) what anatomical and physiological capacities facilitate this superlative performance and such prodigious O2 fluxes (i.e. maximal VO2)? (3) do cardiovascular dynamics or intramuscular energetic processes limit VO2 kinetics (i.e. the speed at which VO2 increases at the onset of exercise)? VO2 kinetics determine the size of the O2 deficit and as such represent an important determinant of muscle metabolism and fatigue; and (4) what determines the efficacy of muscle microcirculatory O2 exchange?

The objective of the present study was to compare the hoof deceleration and ground reaction forces following impact on two different surfaces. Seven unshod Standardbreds were trotted by hand at 3.0–5.7 m s− 1 over a force plate covered by either of the two surfaces, sandpaper or a 1 cm layer of sand. Impact deceleration data were recorded from one triaxial accelerometer mounted on the fore- and hind hooves, respectively. Ground reaction force data were obtained synchronously from a force plate, sampled at 4.8 kHz. The differences between the two surfaces were studied by analysing representative deceleration and force variables for individual horses. The maximum horizontal peak deceleration and the loading rates of the vertical and the horizontal forces were significantly higher on sandpaper compared with the sand surface (P < 0.001). In addition, the initial vertical deceleration was significantly higher on sandpaper in the forelimb (P < 0.001). In conclusion, it was shown that the different qualities of the ground surface result in differences in the hoof-braking pattern, which may be of great importance for the strength of the distal horse limb also at slow speeds.

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.

Degenerative joint diseases, such as osteoarthritis, adversely impact the health of the equine athlete as well as the economics of the equine industry. Our understanding of the aetiology of osteoarthritis, although not nearly exhaustive, has increased substantially in recent years. Molecules, including cytokines, inflammatory mediators, and metalloproteinases, have been identified and associated with the progression of joint disease. Several factors, including trauma to the joint, immobilization, conformation, shoeing, and ageing, have been linked with osteoarthritis. Our continued efforts into elucidating critical biological mediators and risk factors, coupled with better chondroprotective therapies and diagnostic tools, should facilitate our ability to maintain the skeletal health of the equine athlete

Kenyan runners, and especially those originating from the Kalenjin tribe, have dominated international middle- and long-distance running for over 40 years, prompting significant interest in the factors contributing to their success. Proposed explanations have included environmental factors, psychological advantage and favourable physiological characteristics, which may be genetically conferred or environmentally determined. Running is inherent within local Kenyan tradition and culture, and the Kenyan way of life, which involves many outdoor activities and pastimes in addition to mostly unfavourable living conditions, is conducive to enhanced distance running performance. Despite economic deprivation, Kenya has produced world and international running champions repeatedly over the past few decades; these champions have become role models for the younger generations, who take up running in the hope of a better future for themselves. Favourable environmental conditions such as altitude, diet and anthropometry, in addition to the motivational and socio-economic factors mentioned above, have all been proposed as possible reasons for the unsurpassed achievements of Kenyan distance runners. However, the fact that the majority of internationally successful runners originate from a small tribe that accounts for approximately 3% of the total Kenyan population also points to a possible genetic component. Whether this is subject to influence from other co-factors, such as altitude or training effects acquired during childhood, remains as yet unresolved.

Muscle function depends in part on the interplay between its activity and its length within the stretch-shortening cycle. The longissimus dorsi is a large epaxial muscle running along the thoracic and lumbar regions of the equine back. Due to its anatomical positioning, the longissimus dorsi has the capability of contributing to many functions: developing bending moments in the dorsoventral and lateral (coupled to axial rotation) directions and also providing stiffness to limit motion in these directions. We hypothesize that the exact function of the longissimus dorsi will vary along the back and between gaits as the relation between activity and motion of the back changes. Electromyograms (EMG) were recorded at walk (inclined and level) and trot (on the level) on a treadmill from the longissimus dorsi at muscle segments T14, T16, T18 and L2. Back motion was additionally measured using a fibre-optic goniometer. Co-contractions of the muscle between its left and right sides were quantified using correlation analysis. A greater dominance of unilateral activity was found at more cranial segments and for level walking, suggesting a greater role of the longissimus dorsi in developing lateral bending moments. Timing of the EMG varied between muscle segments relative to the gait cycle, the locomotor condition tested and the flexion–extension cycle of the back. This supports the hypothesis that the function of the longissimus dorsi changes along the back and between gaits.

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.

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 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.

Reasons for performing the study: In human exercise physiology, the current gold standard for evaluating aerobic capacity is the measurement of oxygen consumption (VO2) and maximal oxygen uptake (VO2max). The evaluation of VO2 in horses is performed in some laboratories equipped with a treadmill but has only been exceptionally reported in field conditions because of the lack of adapted equipment. Objectives: The aim of this study was (1) to assess the feasibility of VO2 measurement on the track using a recently validated portable breath-by-breath gas analyser system adapted to horses (Cosmed K4b2® and Equimask®), (2) to compare these results with those obtained during a treadmill exercise test and (3) to study correlations between VO2 and physiological parameters usually measured in field condition such as heart rate (HR), lactataemia (LA) and the speed at which HR equals 200 beats per minute (bpm) (V200) or LA 4 mmol l− 1 (VLA4). Methods: Five healthy Standardbred trotters in training were submitted to two stepwise incremental exercise tests, one driven on the racetrack and the other on a high-speed treadmill with a 4% incline. Speed (v), HR, ventilatory parameters and VO2 were continuously recorded throughout the duration of the tests and LA was evaluated after each step. Results: All horses completed the test satisfactorily after an initial acclimatization to the mask. There were marked individual differences in ventilatory strategy, and breathing frequency (Rf) at the higher levels of exercise was noticeably low. The VCO2 measurements were incoherent. There were no significant differences between track and treadmill maximal data obtained during the last step [VO2peak (track: 139.9 ± 8.9 ml kg− 1 min− 1; treadmill: 139.9 ± 13.4 ml kg− 1 min− 1), LAmax (track: 6.5 ± 1.6 mmol l− 1; treadmill: 7.3 ± 3.0 mmol l− 1), HRmax (track: 229 ± 6.2 bpm; treadmill: 222 ± 13 bpm)], although the maximal speed required to reach similar workloads was significantly higher on the track (11.9 ± 0.6 m s− 1vs. 9.7 ± 0.4 m s− 1). The correlation between VO2 and HR (r = 0.87; P < 0.001) and VO2 and LA (r = 0.75; P < 0.0001) during both tests was good but no correlation was found between VO2peak and HRmax, LAmax, V200 or VLA4. Conclusions: This is the first report of a practical portable system to measure VO2 and ventilation continuously during high-speed field exercise tests. However, current mask design markedly influences ventilation and could have prohibited the attainment of VO2max. Furthermore, consistent VCO2 measurements should be implemented by the manufacturers. Potential relevance: Continuous breath-by-breath ventilation and VO2 measurements can be recorded in horses in the field at submaximal levels. With necessary adaptations to the system entailed, this study opens new perspectives in the analysis of physiological and metabolic mechanisms of exercise in the equine species in genuine track conditions.

The study aimed to investigate the effect of speed and incline on EMG activity in the brachiocephalicus muscle and the long and lateral heads of the triceps brachii muscle. Six horses were exercised on a treadmill at walk (1.7 m s-1), trot (4.0 m s-1) and right lead canter (7.2 m s-1) on a 0 and 8% incline. Kinematics (120 Hz) and electromyography (EMG) (2000 Hz) data were collected simultaneously from the left forelimb of each horse. Significant differences in relation to velocity and incline were identified using two-way ANOVA and post hoc Student–Newman–Keuls tests (P≪0.05). The degree of association between timing of peak EMG intensity and the timing of maximum protraction/retraction angles was assessed using ANCOVA. Increases in velocity led to an increase in stride length and reduction in stride duration. Exercise on the incline increased stance duration and decreased swing duration, while limb protraction/retraction increased. The time of peak EMG activity in the brachiocephalicus was highly related to time of maximum limb retraction (r2=0.84). The time of peak EMG activity in the long head of the triceps brachii was highly associated with time of maximum limb protraction (r2=0.87). Increases in velocity and incline both caused an increase in the intensity of the EMG signal from each muscle. Duration of EMG activity was prolonged in the long head of the triceps brachii muscle and in the brachiocephalicus muscle as velocity increased. Treadmill speed and slope therefore both alter the workload placed on forelimb muscles.

This study evaluated the effects of exercise on cardiac troponin I (cTnI) concentrations in healthy, adult horses.

Fifteen fit, healthy horses determined to have a normal cardiovascular system completed a standardized exercise test on a high-speed treadmill. Heparinized blood was collected for plasma cTnI concentrations before maximal exercise, and 1, 3, 6, 9, 12 and 24 h post-exercise. The cTnI concentrations were measured with a commercial system (Stratus CS, Dade Behring, Inc.). Results were analysed by a multivariate ANOVA, where indicated post hoc analysis was done by Tukey–Kramer HSD and significance was placed at p < 0.05.

All horses had elevations in cTnI concentrations after maximal exercise. Values for cTnI trended higher at 3 h (0.066 ± 0.011 ng ml− 1) and 6 h (0.062 ± 0.011 ng ml− 1) post-exercise compared with pre-exercise (0.039 ± 0.007 ng ml− 1), although this did not reach statistical significance. Mean cTnI concentrations were within our normal reference range at all time points, although four individuals were above our normal range after exercise.

These data show that short-term, high-intensity exercise induces a small rise in plasma cTnI in normal horses. This should be kept in mind when evaluating cTnI concentrations in horses that have recently completed intense exercise. In addition, these data suggest that 3–6 h after intense exercise may be the optimal time for measurement of cTnI concentrations in horses with suspected exercise-induced myocardial damage.

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.

This study tested the hypothesis that orange peel (O) and decaffeinated black tea (T) extracts would alter markers of exercise performance as well as exercise-induced mRNA expression for the inflammatory cytokines IL-6, TNF-alpha and IFN-gamma. Nine healthy, unfit Standardbred mares (age: 10±4years, ∼450kg) were assigned to three treatment groups in a randomized crossover design where each horse was administered one of the following; placebo (O; 21 water), black tea extract in water (T; 21) or orange peel extract in water (W; 21), via a nasogastric tube. One hour later the horses completed an incremental graded exercise test (GXT) on a treadmill at a fixed 6% grade with measurements and blood samples obtained at rest, at the end of each 1min step of the GXT and at 2 and 5min post-GXT. An additional set of blood samples for Polymerase Chain Reaction (PCR) measurements of mRNA was obtained before exercise and at 5 and 30min and 1, 2, 4 and 24h post-GXT. The GXTs were conducted between 0700 and 1200h not less than 7days apart. There were no differences (P>0.05) in VO2max, respiratory exchange ratio, run time, velocity at VO2max, core body temperature, haematocrit, creatine kinase (CK), plasma lactate concentrations, HR, right ventricular pressure (RVP) or pulmonary artery pressure (PAP) across treatments. A major finding was that orange peel extract significantly reduced post-exercise VO2 recovery time (W = 112±7, O = 86±6, and T = 120±11s). There was a significant difference in plasma total protein concentration (TP) in the O runs compared with water and T. TNF-alpha mRNA expression was lower in the T runs compared with water and O trials. IFN-gamma mRNA expression levels appeared to be lower in both the T and O extract runs compared with the water trials. The mRNA expression of IL-6 was unaltered across treatment groups. These data suggest that orange peel and black tea extracts may modulate the cytokine responses to intense exercise. Orange peel extract reduced post-exercise recovery time and may potentially enhance the ability of horses to perform subsequent bouts of high-intensity exercise.

Impact is considered the most critical part of the stance phase for the development of chronic articular disorders such as osteoarthritis in the equine distal limb. Modern, synthetic shoeing materials are believed to modify impact and therefore are often used to treat an/r prevent lameness due to chronic joint disorders. Scientific evidence is scarce, however, to prove this. Hoof impact of forelimb was compared quantitatively in a group of horses under three conditions: unshod, classical steel shoes and shod with a synthetic shoe. Twelve sound warmblood horses were trotted by hand on an asphalt track at a mean speed of 3.5ms−1 and measured in a Latin square design (unshod condition, with steel shoes and with polyurethane (PU) shoes) using a triaxial accelerometer that had been fixed to the lateral hoof wall of the left forelimb. The sampling frequency was set at 10kHz per channel. The maximum amplitude of vertical and horizontal, forwar/ackward accelerations at hoof impact was lowest when shod using the PU shoeing condition (P<0.05), but the duration of the impact vibrations was lowest when unshod. PU shoes cause more damping, less friction and slower shock absorption at hoof level compared with the other two conditions and thus modify impact. Synthetic, polyurethane shoes may help in reducing peak vibrations. These short-term effects appear to be promising enough to evaluate PU shoes under field conditions in reducing impact on the longer term after substantial wear and tear. Furthermore, the possible role of synthetic materials in repairing critical tissues or even in preventing osteoarthritis in horses warrants further investigation.

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.