Acute effects of a submaximal 5-km downhill running bout upon uphill walking economy and lower-limb strength in trail runners.

Our aim was to investigate the effects of downhill running (DR) on lower-limb strength and uphill walking (UW) economy, ventilatory pattern, and step kinematics. Thirty-six experienced trail runners (11 females; 45 ± 8 years, BMI: 23 ± 2.4 kg/m2, VO2peak: 57 ± 8 ml O2.kg-1.min-1) completed a cardiopulmonary exercise test to determine first ventilatory threshold (VT1). During a second visit, UW economy at VT1 (5 min at 20% gradient), expressed as vertical oxygen cost (OCvert) and energy cost of transport (ECvert), was tested before and after a DR bout (5 km at -15% gradient; intensity set by matching HR to HR at uphill VT1). Isometric ankle plantar flexion and half-squat strength (PF and SQ) were assessed pre- and post-DR. During UW, minute ventilation (VE), frequency of respiration (FR), tidal volume (VT), step length (SL), and frequency (SF) were recorded. DR did not alter OCvert or ECvert. PF and SQ exhibited small declines (d = -0.49 and d = -0.25, respectively). VE and FR rose slightly (d = 0.17 and d = 0.43, respectively), while VT decreased marginally (d = -0.15). SL remained unchanged, whereas SF dropped slightly (d = -0.15). A 5-km submaximal DR bout did not deteriorate UW economy. However, the ventilatory response shifted slightly towards a more superficial breathing pattern, and a small impairment in lower-limb strength was observed.