Base endurance (BE) must be practiced at a very easy pace, allowing for complete respiratory comfort, and a high heart rate (such as 170 bpm) is incompatible with this training zone.

noli's read

The principle of base endurance is based on aerobic physiology, where intensity must remain low enough for the body to primarily use lipids as an energy source and minimize nervous fatigue. Meta-analyses and studies on training polarization (notably the work of Stephen Seiler) confirm that high-level athletes spend about 80% of their time at low intensity to optimize cardiovascular and mitochondrial adaptations. Running too fast during so-called 'easy' sessions is a classic error that prevents adequate recovery and limits long-term progress. While 170 bpm may be a normal zone for intense effort or competition for some, it is generally well above the aerobic threshold for a recovery run. The advice is therefore scientifically sound and widely supported by sports science literature. There is no exaggeration here; it is a fundamental recommendation for building a sustainable aerobic base.

the sources

1. 1Rosenblat MA, Perrotta AS, Vicenzino B 2019
2. 2Silva Oliveira P, Boppre G, Fonseca H 2024
3. 3Menshikova EV, Ritov VB, Ferrell RE, et al. 2007