Abstract: In order to gain insight into those training regimens that can minimise the risk of fracture in athletic populations, we conducted a large epidemiological study in racehorses. Thoroughbred racehorses provide a suitable model for studying fracture development and exercise-related risk factors in physically active populations. They represent a homogeneous population, undertaking intensive exercise programmes that are sufficiently heterogeneous to determine those factors that influence injury risk. Daily exercise information was recorded for a cohort of 1178 thoroughbreds that were monitored for up to 2 years. A total of 148 exercise-induced fractures occurred in the study population. Results from a nested case-control study showed a strong interactive effect of exercise distances at different speeds on fracture risk. Horses that exceeded 44 km at canter (< or =14 m/s) and 6 km at gallop (>14 m/s) in a 30-day period were at particularly increased risk of fracture. These distances equate to ca. 7700 bone loading cycles at canter and 880 loading cycles at gallop. Fifty-six fractures occurred in the subset of study horses that were followed since entering training as yearlings, when skeletally immature (n = 335). Cohort analysis of this data set showed that, in previously untrained bones, accumulation of canter exercise increased the risk of fracture (P < or = 0.01), whereas accumulation of high-speed gallop exercise had a protective effect (P < 0.01). However, increasing distances at canter and gallop in short time periods (up to one month) were associated with an increasing fracture risk. All training exercise involves a balance between the risk of fracture inherent in exposure to loading and the beneficial effect that loading has by stimulating bone cells to produce a more robust architecture. Results from our study provide important epidemiological evidence of the effects of physical exercise on bone adaptation and injury risk and can be used to inform the design of safer exercise regimens in physically active populations.

Abstract: Between March 1, 2000 and August 31, 2001, a case-control study was conducted on 12 racecourses in England and Wales to identify and quantify the risk factors associated with horse falls in hurdle races. The cases and controls were defined so that variables relating to the horse, the jockey, the race and racecourse, and the jump could be considered. The cases were defined as a jumping effort at a hurdle flight that resulted in a fall, and the controls were defined as a successful jump over a hurdle at any of the 12 racecourses within 14 days before or after the case fall. Conditional logistic regression was used to examine the univariable and multivariable relationships between the predictor variables and the risk of falling. The risk of falling was significantly associated with the position of the jump in the race, and with the distance and speed of the race. A horse's previous racing experience and history were also significantly associated with the risk of falling and horses participating in their first hurdle race were at almost five times greater risk of falling than horses that had hurdled before.

Abstract: REASONS FOR PERFORMING STUDY: Fatalities resulting from horse falls occurring during the cross-country phase of eventing competitions initiated epidemiological investigation of the risk factors associated with horse falls. OBJECTIVES: To identify variables that increased or decreased the risk of a horse fall during the cross-country phase of an eventing competition. METHODS: Data were collected from randomly selected British Eventing competitions held in Great Britain during 2001 and 2002. Data were obtained for 173 cases (jumping efforts resulting in a fall of the horse-and-rider partnership) and 503 matched controls (jumping efforts not resulting in a fall). The risk of falling was modelled using conditional logistic regression. RESULTS: An increased risk of a horse fall was associated with jumping into or out of water; taking off from good-to-soft, soft or heavy ground; fences with a drop landing; nonangled fences with a spread > or =2 m; and angled fences. Other risk factors included riders who knew that they were in the lead within the competition before the cross-country phase; an inappropriate speed of approach to the fence (too fast or too slow); horse-and-rider partnerships that had not incurred refusals at earlier fences; and riders who received cross-country tuition. CONCLUSIONS: This study has identified modifiable course- and fence-level risk factors for horse falls during the cross-country phase of eventing competitions. The risk of horse and rider injury at eventing competitions should be reduced by 3 simple measures; maintaining good to firm take-off surfaces at fences, reducing the base spread of fences to <2 m and reducing the use of fences at which horses are required to jump into or out of water. Risk reduction arising from course and fence modification needs to be confirmed by intervention studies. Potential relevance: Knowledge of factors that increase or decrease the risk of a horse fall can be used by UK governing bodies of the sport to reduce the risk of horse falls on the cross-country phase of eventing competitions, and reduce the risk of horse and rider injuries and fatalities. As one in 3 horses that fall injure themselves and one in 100 horse falls results in fatality to the horse, we suggest that immediate consideration is given to these recommendations.

Abstract: REASONS FOR PERFORMING STUDY: It is recognised that the amount of psychological stress that an animal encounters determines the degree of response of the hypothalamic-pituitary-adrenal (HPA) axis. In human athletes, the added emotive stress of competition is an important element in the adrenal response. The aim of this study was to examine the effect of show-jumping as well as dressage on stress levels by comparing horses' stress response at a horse show compared to their familiar home. METHODS: Fifty-one horses involved in competition were used. EDTA blood samples were collected before exercise, upon arrived to the schooling area (control), and k over a jump or dressage course. After sampling, plasma was separated and stored at -80 degrees C until determinations of cortisol and ACTH were performed. Fourteen healthy horses not involved in competition were used as control group. RESULTS: Competition induced a significant increase in cortisol and ACTH responses in both, jumping and dressage horses and this effect was more apparent in dressage horses. When horses were most experienced, cortisol and ACTH responses were much lower. CONCLUSION: This study shows that competition elicits a classic physiological stress response in horses and that different training programmes induce different responses. It suggests that horses involved in competition can provide a good model to study the exercise-induced stress response.

Abstract: REASONS FOR PERFORMING STUDY: Fractures below the level of the radius or tibia (distal limb fractures) are the most common cause of equine fatality on UK racecourses; however, little is known about their epidemiology or aetiology. Identification of risk factors could enable intervention strategies to be designed to reduce the number of fatalities. OBJECTIVES: To identify horse-level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses. METHODS: A case-control study design was used. Fractures in case horses were confirmed by post mortem examination and 3 matched uninjured controls were selected from the race in which the case horse was running. One hundred and nine cases were included and information was collected about previous racing history, horse characteristics and training schedules. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture. RESULTS: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have trained on a sand gallop, i.e. a gallop described by trainers as being primarily composed of sand. CONCLUSIONS: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal distal limb fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 805-2012 m (4-10 furlongs)/week. POTENTIAL RELEVANCE: The information from this study can be used to alter training schedules in an attempt to reduce the incidence of fatal distal limb fracture in Thoroughbred racehorses. Training should include some gallop work, and further studies, recording the exact level of work, will help to identify an optimum range of training speeds and distances which will reduce the liklihood of catastrophic fracture on the racecourse.