Epidemiology, clinical characteristics, and associated injury risk factors among trail running race entrants in the 2021 Mac Mac Ultra

Abstract

BACKGROUND : There is limited research available on the epidemiology, clinical characteristics and associated injury risk factors in trail running. This gap in research may put trail runners at risk when competing in challenging trail running races. AIM OF THE STUDY : To determine the epidemiology, clinical characteristics and associated injury risk factors among trail runners entered in the 2021 Mac Mac Ultra Race. DESIGN : Retrospective cross sectional study SETTING : 2021 Mac Mac Ultra race, Sabie, Mpumalanga, South Africa PARTICIPANTS : 251 consenting trail runners METHODS : Data gathered during the pre-event medical screening process include trail runners’ demographics (BMI, height, age, running experience, weight), training variables in respect of running (weekly frequency, weekly distance, surface, average pace, shoes, vertical gain, cross-training,), injury history (clinical characteristics of injury, running-related injury (RRI) in the past 12 months, current RRI, severity of injury), history of disease (chronic disease, current illness) and usage of medication (current, chronic medication). Only the injury-related data were analysed in this study. The questionnaire is used in pre-race medical screening at various trail running events across South Africa. Race entrants self-report their injuries sustained in the past 12 months by responding “yes” to the question: “Did you sustain any running-related injuries in the past 12 months?”. Runners currently injured had selected “injury” in response to the question: Do you have a current injury or illness? If “injury” was selected, then additional questions were posed in relation to the four main considerations of the Oslo Sports Trauma Research Center Questionnaire on Health Problems (OSTRC-H) (Clarsen et al., 2013). To be recorded as a current injury, the race entrant had to indicate that training modification was needed during the two weeks before the race. Furthermore, like the study on the 2019 Sky Run Race, questions that fixated on the clinical aspects of injuries were asked. We used the Pearson Chi square test to compare categorical variables of all athletes in the event versus consenting athletes in the event to establish if our sample was demonstrative of the population (all 2021 Mac Mac Ultra race entrants). Frequencies (n, %) of injury for pathology type, tissue type, body area and anatomical region utilised descriptive statistics. Inferential statistics (Independent t-test and Mann Whitney U test, and Chi Squared tests) were applied to contrast the training and demographic data of entrants between injured and non-injured entrants to examine and find connected injury risk factors. Odds Ratios were calculated using Binary logistic regression to investigate further the association between exposure and outcome (sustaining RRIs). Entrants were categorised into those who experienced a RRI during the previous 12 months vs. non-injured participants. Due to zero of the univariate examinations yielding statistically significant results (p<0.05), a multivariate evaluation was omitted. RESULTS : A total of 330 trail runners entered the race, although the questionnaire used at pre-race medical screening was compulsory, participation in the study was not, 251 out of the 330 race entrants gave consent to use their data. Twenty percent of trail runners stated one RRI or more. The retrospective annual incidence was 19.92/100 athlete-years. The point prevalence was 4.4%. Injuries mostly appeared in the lower limb (95%), including the lower leg (26%), thigh (22%), ankle and foot (13%) described as the highest injured body areas. Of tissue type injuries, muscle/tendon comprised 60%. Muscle injury (36%), tendinopathy (24%) and joint sprains (9%) were the most reported pathology types. No related injury risk factors were discovered in this study. CONCLUSION : One in five trail runners reported one or more RRI during the 12 months before a competitive event. Running-related injuries commonly involved the lower limb, especially the lower leg, thigh, foot, and ankle. In this study no risk factors associated with sustaining a RRI was identified, this can be due to the complex nature of injuries.