Trail running is a high-intensity sport in which runners tackle off-road terrains, substantial elevation changes and varying running distances - from a few kilometres to multiday ultramarathons in excess of 200km. Trail running has an estimated 20 million runners participating, and has seen a 15% increase in participation over the past decade. While the health benefits associated with running are well known, trail running also comes with a high risk of injury. This makes it important to identify those runners at risk of injury, prior to participation in training and races, however little is known in this area. Recently, a living systematic review was embarked on to try and identify, summarise and frequently update the available evidence on factors associated with injury in trail running. The review also reported the epidemiology (incidence, prevalence and clinical characteristics) of injury in trail running.

The living systematic review identified intrinsic and extrinsic factors that are associated with significantly higher injury risk in trail running – these included higher running experience, being a level A runner, having a higher total PAD-22 questionnaire score, neglecting a warm-up, not using a specialised running plan, regular training on asphalt, double training sessions per day and physical labour occupations. Risk factors associated with a significantly higher risk for muscle cramping included slower race finishing time, a prior history of cramping, and higher levels of postrace blood urea nitrogen and creatine kinase.

The study found that the lower limb was the most commonly injured anatomical region, specifically the foot/toe, ankle and hip/groin; and that blisters, joint sprains and tendinopathies were the most common pathology types reported in trail running.

The authors noted that limited research in this area and poor quality of evidence restricted the ability to make clinical recommendations. A previous publication on medical support at ultra-endurance races in remote regions provided guidelines for primary medical care at races but also highlighted the importance of risk reduction strategies such as prerace runner education, prerace medical screening and considerations for cancelling races in the presence of extreme environmental conditions. Clear guidance on what runners should be educated on, or the specific factors to consider during prerace medical screening are however unclear. As this living systematic review matures, the authors aim to provide the clinician with evidence-based guidance on injury risk factors to consider for runner education and medical screening either prerace or during training.

Reference for this summary:

Trail running injury risk factors: a living systematic review. Carel Viljoen, Dina C (Christa) Janse van Rensburg, Willem van Mechelen, Evert Verhagen, Bruno Silva, Volker Scheer, Manuela Besomi, Rubén Gajardo-Burgos, Sérgio Matos, Marlene Schoeman, Audrey Jansen van Rensburg, Nicol van Dyk, Susan Scheepers, Tanita Botha. Br J Sports Med Epub ahead of print: doi:10.1136/ bjsports-2021-104858