FIGURE 1.

Spectrum of the types of physical inactivity. Following the arrow from right (low intensity of physical inactivity) to left (high intensity of physical inactivity) shows our estimate of the intensity of physical inactivity per unit of time. Not shown is the volume (intensity × duration) of physical inactivity. For example, spinal cord severance is high intensity and health decrements appear within days. In opposite manner, sitting is low intensity, with long-term health effects not clinically apparent within days, but nonetheless unhealthy when first appearing after many years.