Original ResearchOne in four trail running race entrants sustained an injury in the 12 months training preceding the 2019 SkyRun race
Introduction
Running is a cost-effective mode of physical activity that plays a role in the prevention of lifestyle diseases and premature mortality (Lee et al., 2017). Trail running is a form of physical activity that involves running outdoors on a variety of natural terrains (mountain, desert, forest) where runners are exposed to large elevation changes as presented by the specific natural environment (ITRA, 2020). Irrespective of the health benefits, running still has a high risk of injury (Lopes et al., 2012; van der Worp et al., 2015; Videbæk et al., 2015).
Among recreational road runners an incidence of 7.7 injuries per 1000 h were reported with a significantly higher incidence of 17.8 injuries per 1000 h among novice runners (Videbæk et al., 2015). The knee (28%) was reported as the most common body area injured among road runners (Francis et al., 2019). Cross country runners presented with an incidence of 13.1 injuries per 1000 athletic exposures (training session or event) in a 15-year longitudinal study (Rauh et al., 2000), with the lower leg reported as the most commonly injured body area among both male (35.2%) and female (23.5%) collegiate student cross country athletes (Kerr et al., 2016). With regards to trail running, several studies have focussed on medical encounters related to trail running race participation (Costa et al., 2016; Graham et al., 2012; Krabak et al., 2011; McGowan & Hoffman, 2015; Scheer & Murray, 2011; Vernillo et al., 2016), with only a limited number of studies that investigated training related injury outcomes (Hespanhol Junior et al., 2017). A prospective cohort study among Dutch trail runners reported a mean prevalence of 22.4% for running related injuries (RRIs) sustained during two-weekly follow up periods (Hespanhol Junior et al., 2017). The most common anatomical region of injury was the lower leg (20.6%), followed by the knee (18.9%), and foot (14.9%), with muscle (27.7%) and tendon (23.6%) reported as the most common tissue types affected (Hespanhol Junior et al., 2017). These results, although adding to the literature pool, cannot be generalised to the global trail running population as the Netherlands has a unique landscape characterised by limited elevation changes.
Injury risk factors in trail running are not well studied. A study on Greek trail runners using a small sample size (n = 40) (Malliaropoulos et al., 2015), reported that participants with physical labour occupations, multiple running sessions per day and more running experience were associated with a higher risk for injury (Malliaropoulos et al., 2015). Studies on conventional forms of running include injury risk factors such as body mass index (BMI) (Buist et al., 2010; Kluitenberg et al., 2016; van Poppel et al., 2016), sex (Messier et al., 2018; Ryan et al., 2014) age (Buist et al., 2010; Kluitenberg et al., 2016), and running experience (Buist et al., 2010; Kluitenberg et al., 2016; Vitez et al., 2017). Whether these factors will relate to a higher risk for injury among trail runners requires investigation. As trail running is often hosted in mountainous regions with varying natural running surfaces i.e. narrow single-track or dirt track off-road trails (Mocanu, 2015), factors such as elevation change (steep ascent and descent) and trail running experience need to be investigated as potential injury risk factors among this population.
Certain trail running races, such as the SkyRun in South Africa, are hosted in elevated and remote settings where medical support is extremely challenging with limited resources (Hoffman et al., 2014). Injured runners that are unable to continue running can be exposed to extreme weather conditions and environmental hazards (Hoffman et al., 2014) while awaiting medical support. This emphasises the need to establish injury risk factors with the intention to design specific injury prevention strategies, as the recurrence of an injury during a trail run race may have dire consequences.
This study aimed to investigate the epidemiology and clinical characteristics of RRIs among trail runners during the 12 months leading up to the 2019 SkyRun race. We further aimed to determine a potential association between commonly known injury risk factors in running and trail running specific variables.
Section snippets
Study design
This study used a cross-sectional study design investigating data collected in the two weeks prior to the 2019 SkyRun race.
Participants and data collection
This study formed part of a larger project: “Reducing Injuries and Illness at Adventure Sports Events: A 10-Year Longitudinal Study (2018–2028)” (REC: 460/2018) that was approved by the Research Ethics Committee of the University of Pretoria. This specific study was also approved by the Research Ethics Committee of the University of Pretoria (REC:747/2019).
The population
Demographics of trail runners
A total of 412 trail runners entered the 2019 SkyRun race and 305 trail runners (74.0%) gave consent for their data to be analysed in this study [100 km (n = 193), 65 km (n = 92), 38 km (n = 30)]. An analysis was done to determine if our sample of consenting trail runners were representative of all race entrants with regards to the sex and race distance category (Table 1). The age group categories for all trail run entrants were not publicly available on the race website, and therefore analysis
Discussion
This study is the first to investigate the epidemiology and clinical characteristics of RRIs among trail runners during the 12 months leading up to the 2019 SkyRun race. Our main findings include: 1) 28.2% of participants reported at least one injury during the 12 months showing a retrospective annual incidence of 49.5 RRIs per 1000 h and point prevalence of 1.3%; 2) most injuries occurred in the lower limb (87.3%); 3) the most commonly injured body areas involved the knee (26.5%), ankle
Conclusion
Approximately 1 in every 4 SkyRun trail runners reported at least one injury in the past 12 months. Trail runners training for the 2019 SkyRun reported RRIs that mostly affected the lower limb specifically the knee, ankle and foot. This emphasises the need to establish injury risk factors to assist in the design of specific injury prevention strategies, as the recurrence of injury during a trail run race may have dire consequences.
Funding
None.
Ethical approval
This study formed part of a larger project: “Reducing Injuries and Illness at Adventure Sports Events: A 10-Year Longitudinal Study (2018–2028)” (REC: 460/2018) that was approved by the Research Ethics Committee of the University of Pretoria. This specific study was also approved by the Research Ethics Committee of the University of Pretoria (REC:747/2019). All participants had to give informed consent for their data to be analysed in this study.
Declaration of competing interest
The authors declare that there are no competing interests.
Acknowledgement
Christina de Villiers – Medical director of the SkyRun race that assisted in data collection.
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