Physiological Indicators of Trail Running Performance: A Systematic Review

To provide a systematic overview of physiological parameters used to determine the training status of a trail runner and how well these parameters correlate with real-world trail running performance.

An electronic literature search of the PubMed and Scopus digital databases was performed. Combinations of the terms "trail run" or "trail runner" or "trail running" and "performance" were used as search terms. Seven studies met the inclusion criteria.

Trail running performance most commonly correlated (mean [SD]) with maximal aerobic capacity (71%; r = -.50 [.32]), lactate threshold (57%; r = -.48 [.28]), velocity at maximal aerobic capacity (43%; r = -.68 [.08]), running economy (43%; r = -.31 [.22]), body fat percentage (43%; r = .55 [.21]), and age (43%; r = .52 [.14]). Regression analyses in 2 studies were based on a single variable predicting 48% to 60% of performance variation, whereas 5 studies included multiple variable regression analyses predicting 48% to 99% of performance variation.

Trail running performance is multifaceted. The classic endurance model shows a weaker association with performance in trail running than in road running. Certain variables associated with trail running research (such as testing procedures, race profiles, and study participants) hinder the execution of comparative studies. Future research should employ trail-specific testing protocols and clear, objective descriptions of both the race profile and participants' training status.