Running imposes a natural physical limit on training volume (approximately 10-15 hours/week) due to impact, making volumes as high as those in other endurance sports like cycling impossible.

noli's read

The observation that running limits weekly volume compared to cycling is widely supported by sports physiology. Unlike cycling (a weight-bearing, low-impact activity), running generates repeated mechanical stresses that strain connective and muscular tissues, increasing the risk of overuse injuries if volume is excessive (Hulme et al., 2017, observational study on injuries). Research confirms that workload is limited by tissue recovery capacity rather than cardiorespiratory capacity alone. The idea that athletes would run much more without these constraints is theoretically consistent with the principles of supercompensation, although it remains hypothetical. It is important to note that the 'top 0.1%' is defined not only by hourly volume, but also by density and intensity, aspects less emphasized here. In sum, the argument regarding the biological limit imposed by impact is scientifically robust.

the sources

No named source held this one up — that absence is part of the verdict.