The risk of a horse-and-rider partnership falling on the crosscountry phase of eventing competitions

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<ul><li><p>158 EQUINE VETERINARY JOURNALEquine vet. J. (2006) 38 (2) 158-163</p><p>Summary</p><p>Reasons for performing study: Fatalities resulting from horsefalls occurring during the cross-country phase of eventingcompetitions initiated epidemiological investigation of therisk factors associated with horse falls. </p><p>Objectives: To identify variables that increased or decreasedthe risk of a horse fall during the cross-country phase of aneventing competition. </p><p>Methods: Data were collected from randomly selected BritishEventing competitions held in Great Britain during 2001and 2002. Data were obtained for 173 cases (jumping effortsresulting in a fall of the horse-and-rider partnership) and503 matched controls (jumping efforts not resulting in afall). The risk of falling was modelled using conditionallogistic regression. </p><p>Results: An increased risk of a horse fall was associated withjumping into or out of water; taking off from good-to-soft, softor heavy ground; fences with a drop landing; nonangled fenceswith a spread 2 m; and angled fences. Other risk factorsincluded riders who knew that they were in the lead within thecompetition before the cross-country phase; an inappropriatespeed of approach to the fence (too fast or too slow); horse-and-rider partnerships that had not incurred refusals at earlierfences; and riders who received cross-country tuition. </p><p>Conclusions: This study has identified modifiable course- andfence-level risk factors for horse falls during the cross-countryphase of eventing competitions. The risk of horse and riderinjury at eventing competitions should be reduced by 3 simplemeasures; maintaining good to firm take-off surfaces at fences,reducing the base spread of fences to </p></li><li><p>J. K. Murray et al. 159</p><p>dressage and showjumping on the first day and speed andenduranceon the second day. Three-day events have dressage on thefirst day, speed and endurance on the second day and showjumpingon the final day. The speed and endurance test at 2- and 3-day eventsconsists of 4 phases (Phases A, B, C and D). Phase D is equivalentto the cross-country course at one-day events. During the cross-country phase, the criteria on which competitors are judged includetime, refusals, rider falls and horse falls. There are 5 one-day eventlevels (in ascending order of difficulty): Intro, Pre-novice, Novice,Intermediate and Advanced. Three-day events are also known asConcours Complet Internationale (CCI) competitions, with thedifficulty increasing from 1-star (1*) to 4-star (4*) level. </p><p>Study design</p><p>A matched, prospective, case-control design with a ratio of 3 controls/case was used to test associations between course andfence-, horse-, rider- and event-related variables and horse falls.The use of a 3:1 control:case ratio was used to maximise thepower of the study for the number of cases that could be identifiedin the 2-year data collection period. Fifty-five one-day and 4 two-day eventing competitions were included in the study followingtheir random selection from 329 one-day event and 10 two-dayeventing competitions that were scheduled during the 2001 and2002 British Eventing (BE) seasons. Eventing competitions wereselected randomly for inclusion in the study by assigning anumber to each eventing competition that was scheduled to takeplace during each 2-week period. Randomly generated numberswere then used to select events for inclusion in the study until nomore competitions could logistically be attended during the 2-week period. Only 16 three-day event competitions werescheduled to take place during the study period and all 16 wereselected for inclusion, to maximise data collection from 3-dayevent competitions. Data were obtained for 180 cases and 540 controls. Controls were matched individually by venue andday of cross-country competition, but not by level of competition. </p><p>Case definition and selection</p><p>A case was a jumping effort that resulted in a horse fall on thecross-country phase of an event. A jumping effort was defined ashaving occurred if the horse attempted to negotiate the obstacle. Ahorse fall was defined as the horses shoulders and quarterstouching either the ground or the obstacle and the ground at thesame time (Anon 2001b). In this study, falls were identified andrecorded by fence judges, who were positioned by each fence torecord penalties incurred by each competitor. All horses that fell atselected events were included as cases.</p><p>Control definition and selection</p><p>A control was a jumping effort that did not result in a horse fall. Threecontrols were selected randomly from all successful jumping effortsthat took place on the same day and at the same competition fromwhich their case was selected. Cases were eligible to be selected ascontrols for jumping efforts that occurred prior to their horse fall.Matching was used to control for the potentially confounding effectsof month, weather conditions and geographical location. </p><p>Data collection</p><p>Data were recorded on the day of the competition for course- andfence-level variables. The ground conditions were assessedsubjectively by one of 2 observers (J.K.M., E.R.S.), who workedtogether at the beginning of the data collection period in an attemptto standardise interpretation (Table 1) of the 6 main categories ofgoing (firm, good-firm, good, good-soft, soft, heavy). The 2 observers compared their assessment of ground conditions at 13 events over the duration of the study, to maintain consistencyand reduce any effects of observer bias. The majority (81%) ofevents were attended only by J.K.M.; therefore; discrepancies inagreement between the 2 observers on the assessment of groundconditions were recorded according to J.K.M.s assessment. </p><p>A fence was classified as having a drop landing if the groundsurface at landing was at a visibly lower level than the groundsurface at take-off. Fences were also classified as being angled ornonangled; angled fences were those positioned at an angle to thehorses line of approach. Angled fences and nonangled fences mayconsist of a single or double set of rails (Fig 1). Angled fencesconstructed from a single set of rails (Fig 1a) require minimal widthclearance from the horse, whereas corner fences (Fig 1b) requirethe horse to clear the width between both sets of rails in onejumping effort. Similarly, nonangled fences vary in the width thatthe horse is required to jump (Figs 1c,d). The spread of the fencewas defined as the distance (m) that the horse would be required toclear, measured at the base of the fence. Fences were measured afterthe competition, so that hoof prints could be used to indicate wherethe majority of horses jumped the fence. There was evidence ofmultiplicative interaction between the variables fence angle andspread. A new variable was created that combined these 2 variables. Angled fences were considered as a single category dueto the wide CIs present when different fence width categories wereconsidered separately. Nonangled fences were split into 2 categoriesto allow for the apparent increased risk associated with fences witha spread of 2 m. The new variable was therefore assigned 3 categories (nonangled fence with a spread of </p></li><li><p>160 Risk of a horse-and-rider partnership falling on the cross-country phase</p><p>A letter explaining the study was sent to the riders of all case andcontrol horses within 3 days of the eventing competition. The letterinformed the riders of imminent contact by telephone to complete aquestionnaire related to the event and additional areas such as horseand rider training. The telephone questionnaires were administeredas soon as possible to each rider selected as a case or control, with amean s.d. time between competition and questionnaire completionof 11.3 10.5 days. Questionnaires were completed by 173 caseriders (96.1%) and 503 control riders (93.1%). </p><p>Risk of a horse fall</p><p>The risk of a horse fall was calculated by dividing the number ofhorse falls by the total number of jumping efforts, and was expressedas the risk per 10,000 jumping efforts. The risk was also calculatedas a function of the type of event (one-, 2- or 3-day event).</p><p>Statistical analysis</p><p>All variables were tested for association with falling usingunivariable conditional logistic regression models. The statisticalpackages R (www.r-project.org) and Egret1 were used for dataanalysis. Continuous variables were also categorised into quintilesin the univariable analysis. The fit of the categorical variables inthe model was compared to the fit of the continuous variablesfrom which they were derived by assessing the change in deviance(assuming the change in deviance follows a chi-squareddistribution with n degrees of freedom, where n = number of extraparameters fitted). To reduce the effects of collinearity, continuousvariables were centred by subtracting the mean of the variablefrom all recorded observations (Kleinbaum et al. 1988).</p><p>Variables with a univariable P value </p></li><li><p>J. K. Murray et al. 161</p><p>to the cross-country were less stable as the individual removal of 8 cases and 10 controls altered the OR by &gt;25%. Examination ofthese cases and controls revealed no unusual covariate patterns andthe individuals were therefore left in the dataset. </p><p>Discussion</p><p>This study identified fences with a take-off and/or landing in waterto be associated with a higher risk of a horse fall than fences sitedon good-firm or good ground. Fences requiring a take-off out ofwater were usually sited so that horses would take at least onestride in water before jumping. Fences rarely had both the take-offand landing in water; only 3% (2/75) of water fences included inthis study fitted this description. The increased risk of falling atfences with a take-off in water may have been attributable tomiscalculation of the jump height and take-off point by the horseand/or rider due to the base of the fence being obscured underwater. The increased risk of a horse fall when landing in water maybe due to the drag of the water unbalancing the horse, or may bedue to shadows and reflections on the surface of the water thatmade it difficult for the horse to judge the presence or depth ofwater. Examination of the PPARs associated with the variables oftake-off and landing surfaces suggests that intervention strategiesshould prioritise fences with a landing in water (PPAR = 14%)rather than those with a take-off from water (PPAR = 7%). The</p><p>magnitude of the PPAR indicates the impact that reducing exposureto the variable is expected to have on reducing the number of horsefalls; however, the acceptability of an intervention to thepopulation needs to be considered before recommendations aremade. For example, while the high PPAR of 25% associated withgood take-off ground indicates that modifying exposure to thisvariable might be effective in reducing the number of horse falls,interventions aimed at producing firmer going are likely to beunpopular with riders due to the associated increased risk of injuryto the horse (Parkin et al. 2004). Our earlier findings (Murray et al.2004a) showed an increased risk of injury to horses for falls inwater compared to falls on land (OR = 2.1, 95% CI 1.13.7). Theevidence from these studies suggests that water fences, particularlythose requiring a landing in water, should be considered animportant area of risk on cross-country courses. However, coursedesigners and riders view water fences as an important test of thehorses ability to tackle natural obstacles and these fences are alsopopular with spectators. If the reduced use of fences with a take-offand/or landing in water is unpopular with the organisationsresponsible for rules relating to fence design within the sport ofeventing in Great Britain (BE and the Federation EquestreInternationale), then further research is needed to identify whichfactors associated with these fences, if any, can be modified toreduce the risk of horse falls at fences into and out of water.</p><p>It is possible that equine jumping performance might beenhanced and the risk of falling reduced by the provision of good-firm take-off surfaces at cross-country fences. Firm surfaces are nowcommon in human athletic sports where long jump and high jumpathletes use a firm take-off surface and land on a soft surface to help</p><p>TABLE 2: Multivariable conditional logistic regression model of oddsratios (ORs), 95% confidence intervals (CI) and P values of risk factorsassociated with cross-country horse falls at eventing competitions inGreat Britain (20012002)</p><p>Cases (%) Controls (%) Adjusted* ORVariable (n = 166) (n = 470) (95% CI) P value</p><p>Take-off surfaceFirm/good-firm 69 (42) 242 (51) 1.00Good 75 (45) 214 (46) 2.29 (1.094.82)Good-soft/soft/heavy 10 (6) 9 (2) 15.56 (2.5495.45)Water 12 (7) 5 (1) 49.80 (10.38238.99) </p></li><li><p>162 Risk of a horse-and-rider partnership falling on the cross-country phase</p><p>minimise the risk of injury (Fukuda 1988). Good take-off ground andgood-soft, soft or heavy take-off ground were associated with ahigher risk of a horse fall when compared to firm and good-firmtake-off ground. The condition of the take-off ground might affectthe balance of the horse and thereby contribute to the risk of a fall.Alternatively, riders might consciously or subconsciously adjusttheir style of riding and hence the clarity of the instructions (oraids) that they give to the horse, as their confidence varies inrelation to the ground conditions. Unclear instructions (through theuse of the riders legs, hands and weight distribution) might lead toindecision from the horse and thereby increase the risk of a horse fall.Hence, suboptimal ground conditions may influence the horsesbalance, the riders confidence or the confidence and decision-making ability of the horse-and-rider partnership.</p><p>Reducing the maximum permitted base spread for fencesmight be an effective intervention strategy to reduce the risk ofhorse falls, as indicated by the PPAR associated with this variable(15%). The width of the fence and angle of approach wereidentified as significant risk factors for horse falls. The increasedrisk of a fall associated with nonangled fences having a basespread of 2 m, compared with those with a spread of </p></li><li><p>J. K. Murray et al. 163</p><p>of reporting dressage and cross-country scores (Murray et al. 2004b),more subjective information may be susceptible to reporting bias.Cases may have been more likely than controls to report aninappropriate speed, in an attempt to find an explanation for theirfall. Subjective verification of the speed of a sample of cases andcontrols needs to be conducted to assess whether bias is present. </p><p>The riders knowledge of their position within the competitionat the start of the cross-country phase was associated with the riskof a horse fall. Riders who knew that they were in the lead prior tostarting the cross-country course were at a higher risk and riderswho knew that they were not in the lead were at a lower risk offalling, compared with riders who were unaware of their positionwithin the competition. Horse-and-rider partnerships that achievedexcellent dressage scores (and...</p></li></ul>

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