High-intensity training, when dosed correctly, possesses unique and essential benefits that complement low-intensity (Zone 2) activity.

noli's read

Andy Galpin highlights here the complementarity of training intensities, an approach widely supported by sports science. Research, notably through meta-analyses on high-intensity interval training (HIIT), confirms that this type of effort significantly improves cardiorespiratory capacity (VO2 max) and metabolic health more rapidly than continuous training alone (Source: Sports Medicine, meta-analysis). The assertion that it is a 'unique magic' is a figurative way of describing the specific mitochondrial and enzymatic adaptations that only high intensity can stimulate. It is, however, accurate to specify 'dosed correctly,' as the risk of injury or excessive fatigue increases with intensity (Source: Journal of Science and Medicine in Sport, observational study). The idea is not to reject Zone 2, the fundamental base of endurance, but to recognize that the body benefits from a different adaptive response depending on the type of stress imposed. There is no evidence suggesting that one replaces the other; current literature instead points toward a polarized model where both intensities mutually reinforce each other.

the sources

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3. 3Silva Oliveira P, Boppre G, Fonseca H 2024
4. 4Menshikova EV, Ritov VB, Ferrell RE, et al. 2007