Neuromuscular Fatigue and Perceived Fatigability in the Hours Following a High‐Intensity Endurance Running Depend on the Exercise Protocol

ABSTRACT This study investigated neuromuscular fatigue and perceived fatigability across different high‐intensity endurance running protocols. Twelve males (mean ± SD; : 52.2 ± 6.9 mL/kg/min) ran ∼8.0 km: (i) at the velocity associated to the respiratory compensation point (vRCP; 5 × 8 min bouts ‒ RUN 100%RCP ); (ii) at 30% above vRCP (10 × 3 min bouts ‒ RUN 130%RCP ); and (iii) at 50% above vRCP (20 × 80 s bouts ‒ RUN 150%RCP ). Before and for 6 h post‐exercise, voluntary and evoked contractions of knee‐extensors were assessed, alongside tiredness, leg pain, and perceived recovery. Following all protocols, voluntary activation remained depressed for up to 4 h post‐exercise, while voluntary peak force was reduced for at least 6 h ( p < 0.05). Other neuromuscular function markers reduced ( p < 0.05) according to the protocol. No time × protocol interaction was observed for any neuromuscular function marker ( p > 0.05). Aggregate data (protocol effect, p < 0.05) evidenced greater reduction in neural drive to vastus lateralis (RMS VL /Mw amp ) after RUN 100%RCP (−20%) compared to RUN 130%RCP (−3%) and RUN 150%RCP (−7%); and greater reduction in late rate of force development (RFD; 100–200 ms) and contractile function (Qtw pot ) after RUN 150%RCP (−18% and −8%, respectively) than RUN 100%RCP (−8% and −2%, respectively). Leg pain and tiredness remained elevated ( p < 0.05) for at least 6 h following all protocols. Leg pain and tiredness were greater for up to 4 h and for at least 6 h, respectively, after RUN 150%RCP than RUN 100%RCP (time × protocol interaction; p < 0.05). The choice of exercise protocol influences the extent of reduction in vastus lateralis neural drive, impairments in knee‐extensors contractile function, and perceived fatigability for hours following a high‐intensity endurance running.