Takayama & Aoyagi 2025, Do heart rates of elite marathon runners exhibit room for drift?

Opinion piece reviewing heart-rate behaviour in elite marathoners. World-class runners race at approximately 96% of critical speed — 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).