Center of gravity, center of pressure, and supportive forces during human activities.

Abstract

The magnitude and orientation of the vertical supportive force were measured with a force platform during the following activities of a normal male descending to and ascending from squatting and seated postures, and jumping. Simultaneous photographic records were made of the displacements of the mass centers of body segments. This combination of methods has provided a unique means to: compare vertical forces calculated from the photographic records with the force-platform measurements, differentiate between changes in the applied force and changes in the position of the center of gravity of the body, and differentiate between the excursions of the line of gravity and the action line of the vertical supportive force (center of pressure). The vertical force fluctuated above and below body weight during all test activities. The calculated force patterns approximated the measured patterns. Distinctly different pathways were seen for the center of pressure and the line of gravity with the former fluctuating and the latter moving smoothly. The interaction between the 2 suggests a fundamental servomechanism operable in the control of human posture and motion.