Why do marathon runners have less bone than weight lifters? A vital-biomechanical view and explanation

The center of the modeling threshold range should lie near 1000 microstrain. Modeling normally adjusts bone mass and strength to keep strains from voluntary activities near or below that value, which also lies comfortably below bone's operational microdamage threshold. Prolonged mechanical usage as in marathon running would increase microdamage, but as long as strains stay below the microdamage threshold range, remodeling can repair it and keep it from accumulating. Therefore, greater bone mass and strength would not be needed. This endows bone with, in principle, an infinite fatigue life, whereas inanimate structures always have a finite one. Elegant! This also means that in different people, and as an example, femurs with less bone mass and strength than others became that way because weaker muscles put smaller forces on them.