Short Trail Running Race: Beyond the Classic Model for Endurance Running Performance

Purpose This study aimed to examine the extent to which the classical physiological variables of endurance running performance (maximal oxygen uptake (VO2max), %VO2max at ventilatory threshold (VT), and running economy (RE)) but also muscle strength factors contribute to short trail running (TR) performance. Methods A homogeneous group of nine highly trained trail runners performed an official TR race (27 km) and laboratory-based sessions to determine VO2max, %VO2max at VT, level RE (RE0%) and RE on a +10% slope, maximal voluntary concentric and eccentric knee extension torques, local endurance assessed by a fatigue index (FI), and a time to exhaustion at 87.5% of the velocity associated with VO2max. A simple regression method and commonality analysis identifying unique and common coefficients of each independent variable were used to determine the best predictors for the TR race time (dependent variable). Results Pearson correlations showed that FI and VO2max had the highest correlations (r = 0.91 and r = -0.76, respectively) with TR performance. The other selected variables were not significantly correlated with TR performance. The analysis of unique and common coefficients of relative VO2max, %VO2max at VT, and RE0% provides a low prediction of TR performance (R-2 = 0.48). However, adding FI and RE on a +10% slope (instead of RE0%) markedly improved the predictive power of the model (R-2 = 0.98). FI and VO2max showed the highest unique (49.8% and 20.4% of total effect, respectively) and common (26.9% of total effect) contributions to the regression equation. Conclusions The classic endurance running model does not allow for meaningful prediction of short TR performance. Incorporating more specific factors into TR such as local endurance and gradient-specific RE testing procedures should be considered to better characterize short TR performance.