Abstract: As in other competitive sports, the famous Grand National steeplechase, which is held at Aintree in the United Kingdom and is watched by 600 million people worldwide, sometimes results in injury. By analysing data from the past 15 Grand National races (consisting of 560 starts by horses), we are able to identify several factors that are significantly associated with failure to complete the race: no previous experience of the course and its unique obstacles, unfavourable ground conditions (too soft or too hard), a large number of runners, and the length of the odds ('starting price'). We also find that there is an increased risk of falling at the first fence and at the jump known as Becher's Brook, which has a ditch on the landing side. Our findings indicate ways in which the Grand National could be made safer for horses and illustrate how epidemiological analysis might contribute to preventing injury in competitive sport.

Abstract: The ability to jump over an obstacle depends upon the generation of work across the joints of the propelling limb(s). The total work generated by one hind limb of a horse and the contribution to the total work by four joints of the hind limb were determined for a jump. It was hypothesized that the hip and ankle joints would have extensor moments performing positive work, while the knee would have a flexor moment and perform negative work during the jump. Ground reaction forces and sagittal plane kinematics were simultaneously recorded during each jumping trial. Joint moment, power and work were determined for the metatarsophalangeal (MP), tarsal (ankle), tibiofemoral (knee) and coxofemoral (hip) joints. The hip, knee and ankle all flexed and then extended and the MP extended and then flexed during ground contact. Consistent with our hypothesis, large extensor moments were observed at the hip and ankle joints and large flexor moments at the knee and MP joints throughout ground contact of the hind limb. Peak moments tended to occur earlier in stance in the proximal joints but peak power generation of the hind limb joints occurred at similar times except for the MP joint, with the hip and ankle peaking first followed by the MP joint. During the first portion of ground contact (approximately 40%), the net result of the joint powers was the absorption of power. During the remainder of the contact period, the hind limb generated power. This pattern of power absorption followed by power generation paralleled the power profiles of the hip, ankle and MP joints. The total work performed by one hind limb was 0.71 J kg(-1). Surprisingly, the knee produced 85% of the work (0.60 J kg(-1)) done by the hind limb, and the positive work performed by the knee occurred during the first 40% of the take-off. There is little net work generated by the other three joints over the entire take-off. Velocity of the tuber coxae (a landmark on the pelvis of the animal) was negative (downward) during the first 40% of stance, which perhaps reflects the negative work performed to decrease the potential energy during the first 40% of contact. During the final 60% of contact, the hip, ankle and MP joints generate positive work, which is reflected in the increase of the animal's potential energy.

Abstract: REASONS FOR PERFORMING STUDY: Clinical history and examination are important features in diagnosis of equine back dysfunction. However, interpretation is subjective and therefore may vary substantially. OBJECTIVES: To establish a clinical tool to objectively evaluate the function of the equine back, in the form of a database on the kinematics of the back at the walk and trot in fully functioning riding horses. METHODS: Thirty-three fully functioning riding horses walked and trotted on a treadmill. Morphometrics and kinematics were tested for correlations to age, height, weight and stride length, and differences between gender (geldings and mares) and use (dressage and showjumping). RESULTS: A database for range of movement and symmetry of movement for extension and flexion, lateral bending, lateral excursion and axial rotation was presented. Symmetry values were very high for all variables. Significant differences were observed in use and gender. Age was negatively correlated to extension and flexion of the thoracolumbar junction. CONCLUSIONS: Interrelationships between use, gender and age to conformation and movement were established. POTENTIAL RELEVANCE: The database provides a basis for objective reference for diagnosis, therapy and rehabilitation of clinical cases of back dysfunction.

Abstract: OBJECTIVE: To quantify variation in the jumping technique within and among young horses with little jumping experience, establish relationships between kinetic and kinematic variables, and identify a limited set of variables characteristic for detecting differences in jumping performance among horses. ANIMALS: Fifteen 4-year-old Dutch Warmblood horses. PROCEDURE: The horses were raised under standardized conditions and trained in accordance with a fixed protocol for a short period. Subsequently, horses were analyzed kinematically during free jumping over a fence with a height of 1.05 m. RESULTS: Within-horse variation in all variables that quantified jumping technique was smaller than variation among horses. However, some horses had less variation than others. Height of the center of gravity (CG) at the apex of the jump ranged from 1.80 to 2.01 m among horses; this variation could be explained by the variation in vertical velocity of the CG at takeoff (r, 0.78). Horses that had higher vertical velocity at takeoff left the ground and landed again farther from the fence, had shorter push-off phases for the forelimbs and hind limbs, and generated greater vertical acceleration of the CG primarily during the hind limb push-off. However, all horses cleared the fence successfully, independent of jumping technique. CONCLUSIONS AND CLINICAL RELEVANCE: Each horse had its own jumping technique. Differences among techniques were characterized by variations in the vertical velocity of the CG at takeoff. It must be determined whether jumping performance later in life can be predicted from observing free jumps of young horses.

Abstract: REASONS FOR PERFORMING STUDY: The costs and investments required for the purchase and training of showjumpers justify the need to find selection means for jumping horses. Use of objective kinematic criteria correlated to jumping ability could be helpful for this assessment. OBJECTIVES: To compare back kinematics between 2 groups of horses of different competition levels (Group 1, competing at high level; Group 2 competing at low level) while free jumping over a 1 m vertical fence. METHODS: Three-dimensional recordings were performed using 2 panning cameras. Kinematic parameters of the withers and tuber sacrale (vertical displacement, vertical and horizontal velocities), backline inclination and flexion-extension motion of the 3 main dorsal segments (thoracic, thoracolumbar and lumbosacral) were analysed. RESULTS: Group 2 horses had a lower displacement of their withers and tuber sacrale from the end of the last approach stride until the first departure stride (P<0.05). As a result, they increased the flexion of their thoracolumbar and lumbosacral junctions during the hindlimb swing phase before take-off (P<0.05). However, withers and tuber sacrale velocities were slightly modified. Group 1 horses pitched their backline less forward during the forelimb stance phase before take-off and straightened it more after landing (P<0.05), probably indicating a more efficient strutting action of their forelimbs. CONCLUSIONS AND POTENTIAL RELEVANCE: Because significant differences in back motion were found between good and poor jumpers when jumping a 1 m high fence, criteria based on certain back kinematics can be developed that may help in the selection of talented showjumpers.