An investigation of tracking behavior exhibited during balancing and standing

A simple balance model, defined by a structure based on D.A. Winter´s (1995) concept of the passive mechanics of the body and a concept of manual control based on D.T. McRuer´s et al.´s (1959) crossover model, was applied to different states of human upright standing. The model suggests that the velocity of the center of pressure is proportional to the acceleration of the center of mass, with a time delay. Three subjects performed standing tasks of different levels of difficulty in maintaining balance. These tasks were as follows: (1) standing quietly on both feet; (2) standing on one foot; and (3) standing with raised heels. The data were compared to the model. The time delay parameter of the model was determined with cross-correlation. Values of the time delay ranged from 200 to 450 ms. It is speculated that the range of time delay obtained from these events signify the range of adaptability of the healthy upright human body