This is the first study to provide perspective on medical and non-medical reasons for the cancellation of MMA contests during the pre-bout examination period conducted by an athletic commission. While the descriptive epidemiology is relatively simple, and further investigation of this area is required, it does highlight several areas that require attention.
Abnormalities on Imaging of the Head
The frequency of neuroimaging or incidence of abnormality on neuroimaging in this cohort of athletes that competed in Calgary from January 2010 to December 2016 is not possible to extrapolate. This occurred because the baseline number of athletes that required any neuroimaging (as an example, imaging in the post bout period) could not be determined from CCSC records over the entire study period (records were only maintained for 1 year period before destruction prior to 2014). What can be inferred is that 780 athletes competed over the 7-year study period, and 5 were identified with abnormal neuroimaging that lead to an indefinite suspension in the pre-bout period. Apart from the lacunar infarct finding (Athlete 22 in Table 1 was also a poorly controlled hypertensive patient despite medication, along with electrocardiogram abnormalities), each of the other neuroimaging abnormalities is in keeping with a traumatic head mechanism of injury [28,29,30]. More specifically, there is emerging evidence from MMA and boxing literature suggesting that the microstructural changes observed on these investigations could be related to previously sustained training or competition head trauma [31, 32] and potentially correlate with chronic traumatic encephaolopathy . This is especially concerning as Hutchinson et al. reported a knock out rate of 6.4 per 100 athlete-exposures for MMA athletes, and those who were knocked out on average sustain 2.6 head strikes after they have lost consciousness prior to referee intervention .
The ABC Medical Committee provides minimal guidance on the use of neuroimaging in the pre-bout examination period and no guidance on the use of neuroimaging for post-bout examination . Presently, this is a nebulous area for ringside physicians where there are many more questions than definitive answers. Overarching themes include the following: What is the frequency of screening neuroimaging and does this depend of the athlete’s age? Is neuroimaging warranted after an unsanctioned bout? What are the needs for neuroimaging post traumatic brain injury? What is the appropriate type of neuroimaging? While a thorough review of the literature relating to neuroimaging of head trauma from a combative sport perspective is beyond the scope of this manuscript, the approach to these scenarios would benefit from a consensus or guidelines statement from the ABC Medical Committee or the Association of Ringside Physicians (ARP).
Minimum Medical Screening Standards
The minimum medical screening standards (MMSS) are vitally important as they set a benchmark for what is deemed medically necessary to allow an athlete to compete . The CCSC has used screening medical requirements that are in keeping with the precedent-setting sanctioning bodies in the USA such as Nevada or New Jersey State Commissions [35,36,37]. As such, the CCSC has incorporated screening for infectious blood borne pathogens, pregnancy, and cardiac, ophthalmological, or neurological disease.
Presently, there is no uniformity between commissions across Canada, let alone from the international context, when it comes to MMSS. Review of the MMSS across the members on the ABC website will quickly highlight the wide variations between commissions . This can range from conducting a pre-bout physical the day of the event to a pre-bout physical plus screening for infectious blood borne pathogens, pregnancy, and cardiac, ophthalmological, or neurological disease and additional requirements for older athletes. The ABC Medical Committee has outlined MMSS  for combative sports athletes. However, these are merely suggestions and do not have to be incorporated into a commission’s standard practice for that commission to maintain membership in the ABC. In an effort to create uniformity, the ABC and the ABC Medical Committee should institute MMSS that must be followed by a commission if it is to be entitled to membership in the ABC.
Weight Cutting and Dehydration
The policy around weight cutting is an active area of review for regulatory bodies  with no uniformly accepted approach. In this data set, only a single athlete (Table 1, Athlete 5) was suspended from competition secondary to dehydration in the pre-bout examination period. Surprisingly, this indicates that 0.13% of MMA athletes that reported to the CCSC weigh-in were considered dehydrated. However, there was no formal definition used to determine if athletes were dehydrated or a means to estimate the level of dehydration. As such, it is not possible to infer if this data set is representative of the number of athletes that are dehydrated when they present for weigh-in. There is no literature to support this negligible number of athletes showing evidence of dehydration, instead, there is mounting literature identifying the trends of rapid weight cutting practice in MMA [12, 13, 39] and other combative sports . This literature supports that dehydration has become a normal part of the weight-cutting culture in MMA [12, 13]. A recent investigation by Matthews et al.  studied MMA athletes’ weight-making practices and discovered that at the official weigh-in, 57% of athletes were dehydrated and the remaining 43% were severely dehydrated according to their urinary hydration status. Jetton et al.  identified that 39% of MMA athletes remained significantly or seriously dehydration 2 h prior to competition despite the official weigh-in process having occurred 22 h prior. Dehydration in combative sports has been linked to tangible health consequences. For example, among other risks, it can leave athletes susceptible to closed-head trauma  and transient cognitive impairment  when athletes are still dehydrated.
Over the last year and a half, a new approach has been adopted by some American commissions that allows for an early weigh-in process [42, 43] to give athletes more time to rehydrate before the commencement of the bout in an effort to decrease the aforementioned dehydration risks. Specifically, this new weigh-in procedure offers athletes several more hours than the customary 24 h prior to competition in which to rehydrate. The California State Athlete Commission in May 2017 passed a 10-point weight-cutting regulation  that endorsed the extended rehydration period and proposed several recommendations to curb extreme weight cutting. Alternatively, One Championship has implemented a much more progressive approach to prevent extreme weight cutting . An athlete’s competing weight class is assigned by One Championship based upon their current walking weight and daily training weights. Once the competition weight class has been established, the athlete cannot alter their weight class fewer than 8 weeks prior to the event and One Championship can conduct random weight checks leading up to the event. These two approaches highlight very different interventions—one that tries to reverse the effects of extreme weight cutting and the other that tries to prevent extreme weight cutting from occurring. Intuitively, the longitudinal approach offers a means to reframe the weigh-in process and mitigate extreme weight-cutting practices. However, the adoption of such a process will need to overcome imbedded weight-cutting practices in MMA culture and will require consistent support from the sanctioning and promotional organizations in which the athletes are competing. Beyond the initiation of any new weigh-in practice, there should be further efforts to scientifically validate the need for such measures and subsequent investigation to show that the new practice is creating a healthier or safer process of the athlete.
Support for Athletes to Withdraw from Competition
According to the data, two athletes (Table 1, Athletes 1 and 8) withdrew from competition of their own volition secondary to injuries. In each of these incidences, the athletes sought the withdrawal from competition after conferring with the ringside physician. Partaking in amateur or professional MMA bouts creates not only an internal spirit of competition in the athlete but also external expectations from their coaches, the promotional organization, and the fans . Having a medical team that is not affiliated with any of these groups provides credibility and support for the athlete’s health concerns and creates a space where the athlete can make an informed decision regarding competition [46, 47].
Developing Competent Ringside Physicians
Establishing a competent group of ringside physicians with a consistent approach to peri-competition medical screening and suspensions is essential for athlete safety. As there continues to be wide variation in local practice by commissions  when it comes to screening for head-related trauma, MMSS, and weigh-in procedures, ringside physician groups need to work collaboratively to aid with mentoring any new physician that joins the group. The creation of a competent group of ringside physicians that understands not only the medical aspects of care but also the regulatory, social, and economic forces within MMA is necessary when balancing athlete safety. To further develop ringside physician competency, the ARP, along with the American Colleague of Sports Medicine, provides the Certified Ringside Physicians program . In addition, the ARP offers many online resources to assist physicians with peri-competition medical screening and health challenges, as well as continuing medical education .
Training and Bout Cancellation
Injury disclosure by an athlete (Table 1, Athletes 1 and 8) that prevented them from competing in sanctioned contests in Calgary from January 2010 to December 2016 accounted for 8% of cancelled bouts or 36.6 injuries per 100,000 athlete-years (calculated as [2/(780 × 7)] × 100,000). It is not possible to ascertain from the data if these injuries were related to training or another mechanism of injury. Even if it is assumed that these two injuries occurred during training, this is a low occurrence of training-related injuries. A single study from the MMA literature reported training-related injuries as 376.4 per 100 athletes (the time frame for this study could not be determined) . The literature on training-related injuries in other combative sports shows the following: for boxing, it is reported as 16.2 to 19.2 per 100 athlete-year [50, 51]; for karate, its ranges from 20.2 per 100 athletes (the time frame for this study could not be determined)  to 45.2 per 100 athlete-year ; for taekwondo, it is reported as 7.1 to 92.8 per 100 athlete-year [50, 54]; for judo, it ranges from 8.2 to 29.6 per 100 athlete-years [50, 55]; and for wrestling 132.0 per athlete-years  has been found. Additionally, there is a spectrum when it comes to the proportion of injuries occurring in the training phase of different combative sports: for boxing, it is 5.3 to 42.9% [50, 51]; karate, it is 75.9% ; taekwondo, it is 36.0 to 81.5% [50, 54]; judo, it is 11.6 to 70.0 [50, 56]; and wrestling, it is 63.0% . It is not clear why there is such a large discrepancy between the existing literature and the rate of presumed training-related injuries in this study. However, this may be explained by any of the following reasons: bouts were cancelled due to athlete injury by the promoter before the pre-bout examination period; athletes were not volunteering the existence of injuries; the screening techniques employed by ringside physicians did not detect the injuries; or the injuries were considered minor by the ringside physician and medical clearance was given. Ultimately, additional study of the pre-competition period is necessary to better quantify the existence and frequency of injury during this phase of a MMA athlete’s career.
Matchmaking and Combative Sports Commission Oversight
Cancelled bouts in the pre-bout examination periods represented 5.4% of all MMA bouts in Calgary over the study period. When looked at from a MMA promotional organization standpoint, the average bout cancellation percentage is 13.2% (± 24.9, 0–63.6). However, promotional organization D (Table 2) appears to be an outlier at 63.6%, and if this is removed, the average bout cancellation percentage drops to 3.1% (± 3.0, 0–6.7). There is presently no combative sports literature that reports on the occurrence of cancellations in the pre-bout period for comparison.
What is highlighted by this finding is a consistent bout cancellation percentage for all organizations but one. This large discrepancy for promotional organization D could be related to the following: the small number of events and bouts held by the organization, limited experience with the matchmaking process, or its ability to attract seasoned amateur and professional athletes may have been limited as it was a younger organization in Calgary. However, promotional organizations B, C, E, and F would also be considered young organizations in Calgary and did not suffer from the same large bout cancellation percentage. The CCSC is responsible for licencing promotional organizations, along with the athletes, and approving the matchmaking process. As such, it behoves the commission to guide new or younger promotional organizations through the matchmaking process to ensure that athletes are safely chosen to engage in competition prior to the pre-bout medical examination. Alternatively, if there is an emerging pattern of athlete safety concerns, as noted by cancelled bouts, then the commission should consider not granting a licence to such a promotional organization.