Training Zones

The concept of exercise training zones is not merely a coaching tool; it is a fundamental framework that maps the continuous spectrum of human physical effort to the ways in which the body produces energy, recruits muscle fibres, and preserves homeostasis. Intensity zones serve as a central organising principle in cycling coaching and exercise science, providing a framework for prescribing and monitoring training intensity. Historically, exercise intensity was often prescribed through intuitive perception of effort ( Birk and Birk, 1987 ) or through arbitrary percentages of maximal anchors such as maximal heart rate (HR max ), maximal oxygen uptake (V̇O 2max ), and peak power output attained during an incremental test ( Ẇ max ) ( Kuipers et al. , 1985 ; Mann et al. , 2013 ). While these methods help practitioners structure exertion, they do not fully account for the complex internal milieu of athletes ( Coyle et al. , 1988 ; Gass et al. , 1991 ; Iannetta et al. , 2020 ). A recent consensus statement by the American College of Sports Medicine and Exercise and Sport Science Australia highlights this limitation, noting that arbitrary percentages fail to capture individual metabolic differences ( Bishop et al. , 2025 ).