Figure 1.

Illustration of the Energetic Pathway of Mobility by Schrack et al. with premises noted. With age: 1) energy capacity declines while 2) the energy cost of unrestricted mobility increases. Mobility limitations occur when the energy cost of unrestricted mobility approaches the maximum level of energy a person is capable of expending (i.e., energy capacity). Mobility restrictions are a compensatory strategy for the age-related increase in the energy cost of unrestricted mobility.