Takayama & Aoyagi 2025, Heart-rate drift in elite marathon runners

Analysis of heart-rate behaviour in elite marathoners. World-class runners race at or above their first metabolic threshold with little to no cardiac reserve early on, so any later heart-rate decoupling reflects a drop in running speed rather than an internal heart-rate limit. The further inference, that easy-day pace for the very fit is governed by musculoskeletal load and recovery rather than by a heart-rate zone, is a reasoned extrapolation rather than a directly tested finding. Limited (interpretive).