Cardiorespiratory Responses to Downhill Versus Uphill Running in Endurance Athletes.

PURPOSE: Mountain running races are becoming increasingly popular, although our understanding of the particular physiology associated with downhill running (DR) in trained athletes remains scarce. This study explored the cardiorespiratory responses to high-slope constant velocity uphill running (UR) and DR.

METHOD: Eight endurance athletes performed a maximal incremental test and 2 15-min running bouts (UR, +15%, or DR, -15%) at the same running velocity (8.5 ± 0.4 km·h-1 ). Oxygen uptake ([Formula: see text]O2 ), heart rate (HR), and ventilation rates ([Formula: see text]E ) were continuously recorded, and blood lactate (bLa) was measured before and after each trial.

RESULTS: Downhill running induced a more superficial [Formula: see text]E pattern featuring reduced tidal volume (p < .05, ES = 6.05) but similar respiratory frequency (p > .05, ES = 0.68) despite lower [Formula: see text]E (p < .05, ES = 5.46), [Formula: see text]O2 (p < .05, ES = 12.68), HR (p < .05, ES = 6.42), and bLa (p < .05, ES = 1.70). A negative slow component was observed during DR for [Formula: see text]O2 (p < .05, ES = 1.72) and HR (p < .05, ES = 0.80).

CONCLUSIONS: These results emphasize the cardiorespiratory responses to DR and highlight the need for cautious interpretation of [Formula: see text]O2 , HR, and [Formula: see text]E patterns as markers of exercise intensity for training load prescription and management.