Effect of ground technicity on cardio-respiratory and biomechanical parameters in uphill trail running

The goal of this study was to analyse the effects of ground technicity on cardio-respiratory and biomechanical responses during uphill running. Ten experienced male trail-runners ran ∼10.5 min at racing pace on two trails with different (high and low) a priori technicity levels. These two runs were replicated (same slope, velocity, and distance) indoor on a motor-driven treadmill. Oxygen uptake, minute ventilation (V̇_E), heart rate as well as step frequency and medio-lateral feet accelerations (i.e. objective indices of uneven terrain running patterns adjustments) were continuously measured throughout all sessions. Rating of perceived exertion (RPE) and perceived technicity were assessed at the end of each bout. Oxygen cost of running (O₂Cr) (+10.5%; p < 0.001), V̇_E (+21%; p < 0.004) and the range and variability of feet medio-lateral accelerations (+116% and +134%, respectively; p < 0.001), were significantly greater when running on trail compared to the treadmill, regardless of the a priori technicity level. Despite perceived technicity being lower on treadmill (p < 0.001), RPE was not different between trail and treadmill runs (p < 0.68). It is concluded that running uphill on a trail vs. a treadmill significantly elevates both O₂Cr and magnitude/variability of feet medio-lateral accelerations but no difference could be identified between trails of different a priori technicities. These results strengthen the need for trainers and race organisers to consider terrain technicity per se as a challenging cardio-respiratory and biomechanical component in uphill trail running.Highlights Ten experienced male trail-runners ran ∼10.5 min at racing pace on two trails with different a priori technicity levels. The two runs were replicated (same slope, velocity, and distance) indoor on a motor-driven treadmill.Oxygen cost of running (O₂Cr), minute ventilation (V̇_E) as well as medio-lateral feet accelerations (i.e. objective indices of uneven terrain running patterns adjustments) were continuously measured throughout all sessions. Rating of perceived exertion (RPE) and perceived technicity were assessed at the end of each bout.O₂Cr (+10.5%; p < 0.001), V̇_E (+21%; p < 0.004) and the magnitude and variability of feet medio-lateral accelerations (+116% and +134%, respectively; p < 0.001) were significantly greater when running on trail compared to treadmill, regardless of the a priori technicity level. Despite O₂Cr being different between trail and treadmill runs, RPE was not.Thus, running uphill on a trail vs. on a treadmill significantly elevates both O₂Cr and magnitude/variability of feet medio-lateral accelerations but no difference could be identified between trails of different a priori technicities.