Abstract Quantitative assessment of the fluctuations of the body centre of mass (CM) while in a stationary bilateral stance on a firm surface is an important criterion of the functional state of human motor-vestibular and sensory apparatus. From analysis of the literature we conclude that more objective characteristics of human balance in quiet standing may be the amount of energy used to maintain the CM in a constant position. Further analysis of the references showed that these characteristics have not been investigated in neurological practice. In this study, the displacement of CM in participants standing in a normal anatomical position was analysed. Forty-five healthy women in three age groups: 18–24, 45–55 and over 60 years participated in the experiments, which consisted of recording changes in partial body weight on the force platform (under one leg) in situations with opened and closed eyes. The specific power of oscillation of body sway and force of lateral swing of CM were calculated. Results indicated that the maximum specific power of oscillation and force of lateral swing were observed in the group of women older than 60 years, especially in the absence of vision. Minimum values occurred in the group of 18–24 years. We also found a considerable variability in all indices in all age groups. This indicates that the stability of the vertical posture in humans depends also on the individual biological characteristics of the central nervous and muscular systems.