A Retrospective Survey of Injuries Occurring in Dogs and Handlers Participating in Canicross

Abstract Objectives Canicross is a popular canine and human cross-country sport. The purpose of this study was to identify the most common injuries, their severity, risk factors and the recovery. Methods An internet-based retrospective survey design was used to examine the characteristics of injuries, demographic and competition information and associations with injury rate. Results A total of 160 surveys were received and indicated that at the time of the survey 21.9% of dogs (35/160) had experienced at least one injury. Lacerations, abrasions and punctures were the most common injury type (22/49), most frequently occurring in the footpads of the forelimb (13/16). The majority of dogs (38/49) recovered from their injuries. Sixty-nine out of 147 of the human handlers experienced injuries while competing; ankle injuries (25/69) and bruises, cuts and grazes (20/69) were the most common injuries. Risk factors for injuries were being a purebred Labrador, dogs running with another dog and additionally competing in agility. Conclusions Labradors, dogs running with another dog and dogs also participating in agility competitions were at higher risk for injury. Injuries of the footpads of the forelimb were the most common injuries in dogs. Most dogs had a complete recovery from their injuries. Clinical Significance This is the first study that gives us insight into injuries occurring in dogs and handlers competing in canicross. This will help making recommendations for this sport as well as enable veterinarians to understand the risks and injuries.


Introduction
As with any sport, there is a potential for injury during training and competition, and illness and injuries obtained outside of running may affect athletic performance as well. Studies have been done to investigate demographics and injuries in canine sports such as agility and greyhound racing. A survey of American agility dog handlers conducted in 2009 found that 33% of the 1,627 dogs had been injured, with 58% of the injuries occurring during agility competition. 10 Results of another study on 1,669 agility handlers and 3,801 dogs found that of the agility-related injuries, soft tissue strains, sprains and contusions to the shoulder, back, phalanges and neck were the most commonly reported injuries. 11 In greyhound racing, of nearly 500 injuries reported at two Massachusetts-based racing tracks, fractures were the most common type of injury making up 74.4% of the reported injuries, 12 and it has been previously reported that stress fractures of the carpal, metacarpal, tarsal and metatarsal bones are common in these dogs. [13][14][15][16][17][18][19] These studies show that the potential for injury in canine athletics is high and injury type may vary depending on the sport. Therefore, a canicross-specific injury study could be valuable; as to date, there is limited information available on dogs involved in canicross. To accomplish this, we surveyed handlers about their dog's participation in canicross. The objectives of this study were to characterize the demographics and injuries incurred by both human and canine canicross runners and determine if there are any associations or risk factors involved in these injuries.

Materials and Methods
A retrospective survey design was used to examine demographic information about dogs and their handlers involved in canicross as well as frequency of competitions and training, and injuries sustained. 20 The participants were handlers of dogs involved in the sport of canicross. Several canicross organizations were contacted and handlers participated voluntarily. The survey was approved by the Royal Veterinary College Research Ethical Review Board before being released. The responses to the survey were collected between 21 July 2015 and 11 September 2015.
Demographic questions (age, sex, breed of dog), competition information (location, years competing, race distance, competitions/year, number of dogs running with handler, participation in other sports, being retired and why) and questions on competition preparation (frequency of training/ week, fitness maintenance, exercises prior and after the race) were included in the survey. Participants were asked about the injuries suffered (number, type and location and recovery status) and effect on their competition activity. The severity of the injuries was classified as mild, if dogs recovered in 1 month or less, and severe if it took more than 1 month. This was based on a previous article that examined agility-related injury in dogs. 11 Information regarding whether these injuries were evaluated and treated by a veterinarian, or if they were obvious for the handlers and managed by them, was not included in this survey. Similarly, requirement for any veterinary input into the determination of suitability to return to competition was not included in the survey.
Handlers were also asked demographic questions about themselves (age, sex and years competing), as well as information about injuries sustained.
Descriptive statistics were calculated for several variables. Pearson's χ 2 tests of independence and contingency tables were used to examine associations between injury and various factors. For those variables with expected values of 5 or less, Fisher's exact test of independence was used to correct for small sample size. T-Tests were used for calculating differences between frequency of injury types, location of injury and proportions of injured dogs and humans. Statistical software (SPSS; IBM SPSS Statistics, IBM United Kingdom) and a spreadsheet software (Microsoft Excel; Microsoft Campus, Thames Valley Park, Reading) were used for the analysis. P-Values of < 0.05 were accepted as significant. Sixty-eight dogs out of a total of 160 (42.5%) participated in one or more canine sports in addition to canicross with a total of 19 sports listed. The most common being agility (40/ 68), bikejor (20/68) and scootering (10/68). In bikejor and scootering, the dog is also attached to and pulls the human handler, who is on a bike or a scooter, respectively. Additionally, 33.8% (54 out of 160) of dogs received one or more treatments as fitness maintenance. The most common of these were massage therapy (32/54), hydrotherapy (15/54) and chiropractic therapy (11/54 The majority of the handlers in the survey were female, with a mean AE standard deviation age of 38.3 AE 9.8 years (range, 16-64 years). Handlers' years of experience running in canicross events ranged from less than 1 to 20 years. The greatest number of participants had been running with their dog for less than 2 years (57/134 [42.5%]), followed by participants running for 2 to 4 years (49/134 [36.6%]) and participants running 5 years or more (28 /134 [20.9%]).

Results
Out of the 160 dogs, 8.1% (13) had been reported with an orthopaedic, neurological or systemic disease. The most common of these was hip dysplasia (4/13) and epilepsy (3/ 13). Of these diseases, three participants said that the disease interfered with their dog's competition activity. Of the 160 dogs, 21.9% (35) had sustained one or more injuries since they started running canicross. The anatomical location of injuries is summarized in ►Table 2. Of these dogs, 24 had incurred one injury, 8 had incurred two injuries and 3 had incurred three injuries since they began running canicross. Out of the 49 reported injuries, the most common type of injury was lacerations, abrasions and punctures (22/49), followed by muscle and tendon injuries (8/49). The most common area for lacerations, abrasions and punctures was to the footpads (16/22), specifically the footpads of the forelimb  (13/16). Dogs had recovered back to full running performance from 38 out of 49 of the injuries. Of the reported recovery times for injuries that had completely recovered, 23 out of 33 took less than a month to recover, while the remainder 10 took greater than 1 month to recover. Severity and occurrence of injuries is summarized in ►Figs. 1 and 2. It was found that purebred Labradors were more likely to be injured than other breeds (two-tail p ¼ 0.042). All of these injuries were lacerations, abrasions and punctures (3) or nail tears (2), and all occurred while training for canicross. While Labradors accounted for 1.6% (n ¼ 2/125) of uninjured par-ticipants, they made up 14.3% (n ¼ 5/35) of the injured population. No significant association was found between injury occurrence and the other most common breeds, or between injury occurrence in mixed breeds when compared with purebred dogs (p ¼ 0.463). When evaluating dogs that also competed in agility and bikejor, there was no significant difference in injury occurrence between dogs that participated in bikejor and those that did not (p ¼ 0.150). However, canicross dogs that also participated in agility were more likely to have sustained two or more injuries than those that did not (p ¼ 0.006). No significant association with injury Fig. 1 Type and severity of reported injuries in canicross dogs. Severe injuries are classified as those taking greater than 1 month to recover and current injuries that have not yet recovered and have been on-going for greater than 1 month. Mild injuries are classified as those that took 1 month or less for recovery. Injuries in which the recovery time was not specified or injuries that have been on-going for less than 1 month are classified as unknown severity. Results of χ2 analysis with Yates correction for continuity indicated significant difference in severity across injury types (p ¼ 0.009). CCL injury, cranial cruciate ligament injury. occurrence was found with variables such as sex of dog, neutering status, fitness maintenance, warm up and cool down exercises, distance run, number of competitions/year and number of training days (p > 0.05). Results of χ 2 analysis indicated that there was a significant difference in injury occurrence between dogs that ran alone with their handler and dogs that sometimes or always ran with another dog during canicross, with dogs that ran as a sole dog being less likely to be injured (p ¼ 0.028). There was no significant difference in injury occurrence of humans who ran with one dog and humans who sometimes or always ran with two dogs during canicross (p ¼ 0.526).
Of the human canicross runners, 46.9% (69 out of 147) had suffered one or more injuries while running with their dog. The most commonly reported injuries were ankle injuries (25/69), bruises, cuts and grazes (20/69), knee injuries (13/69) and hip injuries (7/69). Human runners were significantly more likely to be injured than canines (p < 0.0001). Results of χ 2 analysis did not indicate a significant correlation between injury status in humans and injury status in the dog with which they run (p ¼ 0.550).
Humans who have been running in canicross events for 5 years or less were less likely to be injured than those running in canicross for more than 5 years (p ¼ 0.030). Dogs running in canicross events for greater than 2 years were more likely to have incurred two or more injuries than dogs running in events for 2 years or less (two-tail p ¼ 0.001).

Discussion
Results of this study indicated that injuries affected approximately 22% of canicross dogs, with 38% of these injuries occurring during canicross training or competition. This is a smaller proportion of dogs than those that were injured in studies done on agility dogs. 10,11,21 A possible explanation for this result could be that agility dogs have more variation in demands on the body with the many different obstacles they encounter during agility competition and more extreme forces exerted on them while jumping in agility compared with running canicross. 10,22 In addition, dogs injured during canicross seemed to incur more minor injuries with a shorter recovery time when compared with the studies investigating dogs injured during agility and greyhound racing. [10][11][12]18 However, this survey revealed serious injuries that forced the retirement from competition indicating that there is the potential for more serious injury to occur.
It was observed that length of time running in canicross had some effect on injury occurrence, as dogs running in canicross events for greater than 2 years were more likely to have incurred two or more injuries. This is in contrast to results observed in agility dogs, where it has been observed that dogs competing in agility for more than 4 years are at a decreased risk of injury, probably due to an increased expertise and skill acquisition, putting themselves at a lower risk of injury. 11 However, in agility there are a variety of obstacles that would require skill training, in contrast to a more uniform and repetitive activity such as that present in canicross. Although skill improvement could decrease the risk of injury in skill demanding sports, it would be reasonable to think that the longer a dog has been participating in a sport, the higher is the likelihood it has suffered one or more injuries in its career. The incidence of injuries in racing greyhounds has been reported to increase during the second year in a survey, but other factors, such as racing track characteristics and racing speed, could also have influenced the risk of injury. 23 Humans running in canicross for greater than 5 years were also more likely to be injured. Injuries in runners have been reported in 17 to 79% of people, with some variability between men and women, and different factors increasing the risk of injury, such as previous injuries or the use of orthotics. 24 Although both dogs and human runners may develop over-use injuries and stress fractures secondary to their increased activity, 14,17,21,25,26 the intensity of the activity, rather than the duration, may play a more important role in the development of injuries. 21,24,27 However, in the study presented here we did not find a significant relationship between length of races, number of competitions entered per year or training days per week and injuries. Labradors running canicross were more likely to be injured than other dogs, with an odds ratio of 10.25. The proportion of injured Labrador Retrievers (14.3%) was much higher than the proportion of this breed in the study (4.21%). Labrador Retrievers are commonly affected by certain orthopaedic conditions including cranial cruciate ligament disease, hip dysplasia and elbow dysplasia. 28-31 Some orthopaedic conditions have been reported to alter the kinetics and kinematics of affected animals [32][33][34] and it is uncertain if these could play a role in the injuries found in this survey. Dogs that ran with another dog during some or all canicross events were more likely to get injured when compared with those that ran only with a handler. There is no evidence of this happening in other sports where dogs run in groups, such as sled, so it is hypothesized that the presence of two dogs running together may also cause a behaviour that is more likely to get a dog injured, such as deviation from a steady running path and interference with gait or twisting of leads due to the presence of two dogs, which could potentiate injury. Canicross dogs that also participate in agility were more likely to incur two or more injuries. This suggests that risk factors for injury in canicross dogs may include breed, number of dogs running together in canicross events and additional participation in agility. While there was no significant association found between injury occurrence and fitness maintenance, or warm up and cool downs during event, there may be differences in the value of different techniques as results of the survey indicated employment of so many diverse fitness maintenance and warm up and cool down techniques.
Lacerations, abrasions and punctures of the footpads of the forelimb were the most common injury type and site of dogs involved in the survey population. While the forelimb may be more likely to be injured simply because it hits the ground of a potentially hazardous surface before the hindlimb, other mechanisms may also be at work. Further studies are needed to investigate this. Lacerations, abrasions and punctures can be problematic as they can lead to infection and more serious injuries, which could affect future athletic performance, and therefore prevention is important. 25 Protective paw wear such Veterinary and Comparative Orthopaedics and Traumatology Vol. 31 No. 5/2018 as boots, particularly for the front paws, may be useful in preventing this type of injury. In a study undertaken on working dogs at a rescue site found that footpad injuries were the most common injury in these dogs (18/20), but paw injuries were not incurred while dogs were wearing paw protection. Recommendations for the development of safe and effective paw protection that does not hamper agility during this type of work were made in that study. Many of these handlers reported that their dogs wore boots during training. 35 Similarly to these findings, paw protection may possibly be helpful during canicross courses and training in preventing footpad injuries although further studies would be needed. Protective canine boots are being used on police dogs in Germany and other canine sports such as sled dog racing with a multitude of different brands and designs available for dogs. 36 Humans participating in canicross were found to be more likely to be injured than their dogs with 47% of canicross human runners in the survey having experienced an injury associated with running with their dog compared with the 22% of canicross dogs that were injured. The most common injuries found in human canicross runners in this survey were injuries to the ankles, knees and hip as well as bruises, cuts and grazes. This made lacerations and abrasions a common injury finding in both human and canine canicross runners. This is similar to other studies performed in human runners where incidence of injury varies between 19.4 and 79.3%, and the lower extremity is a common site for injuries. 24,25 A study looking into injuries among handlers and dogs competing in agility, also found a higher occurrence of injury in the handlers (14.1%) in comparison with the dogs (8.81%), with similar injuries to our study. 26 There is the possibility that human-reported injuries may be greater and more specific partially due to the ability of humans to communicate the specific pain, which is a limitation when reporting canine injury; however, as there was such a large proportion of humans injured from running with their dogs with 25 different human injury types reported in this study, future studies looking at human injury and risk factors in canicross are warranted.
Limitations of this study should be evaluated when interpreting the results. The accuracy of these findings depends on handler-reported data and recall compared with veterinary-confirmed injuries. Another limitation is self-selection bias as survey respondents volunteered to participate in the survey. It is possible that handlers with a greater interest or personal experience with dogs injured in canicross were more likely to complete the survey. However, studies have found that self-selected survey respondents who care about the issue being studied are more likely to provide complete and higher quality data than randomly selected respondents. 37, 38 There was no confirmation that the injuries encountered by the dogs had been evaluated or treated by veterinarians. Although the more obvious injuries, such as lacerations and abrasions, or nail tears, could have been easily identified by the handlers, other more subtle injuries could have been missed or wrongly localized by the handlers and therefore may not have been properly diagnosed by a veterinarian, and reported in this survey. The majority of injuries found were self-evident, so it is hoped that this limitation would not change the results of this study significantly. Similarly, there was no requirement for any veterinary input into the determination of suitability of a dog to return to competition, so it is unknown if this decision was made on the basis of a veterinarian evaluation or not. It has been reported that subjective lameness evaluation differs among evaluators, even experienced ones, and it is poorly correlated to objective evaluation of the gait. 39,40 However, in addition to lameness evaluation, veterinarians usually perform an orthopaedic examination, which could have influenced the decision further. If the decision to return the dog to competition was made by the handler, other factors, such as competitive or economic reasons, could have biased the choice. It is unclear how all these factors would have influenced the decision to return a dog to competition, and the results of this study.
Return to competition is one of the ultimate goals in recovery from athletic injury, which is not a consideration with non-competition pets. Return to competition after injury was high in canicross dogs in this survey population with dogs having recovered to full performance from 77% of their injuries. However, the athletic performance of most of the injured dogs was affected while they had the injury. The results of this study also suggest that risk factors for injury in canicross dogs may include breed, number of dogs running together in canicross events and additional participation in agility.

Funding
None.