Temporal features of postural adaptation strategy to prolonged and repeatable balance perturbation.
Aim of this study was to get insight into the features of the postural adaptation process, occurring during a continuous 3-min and 0.6Hz horizontal sinusoidal oscillation of the body support base. We hypothesized an ongoing temporal organization of the balancing strategy that gradually becomes fine-tuned and more coordinated with the platform movement. The trial was divided into oscillation cycles and for each cycle: leg muscles activity and temporal relationship between Centre of Mass and Centre of Pressure A-P position were analyzed. The results of each cycle were grouped in time-windows of 10 successive cycles (time windows of 16.6s). Muscle activity was initially prominent and diminished progressively. The major burst of Tibialis Anterior (TA) muscle always occurred at the same time instant of the platform oscillation cycle, in advance with respect to the platform posterior turning point. This burst produced a body forward rotation that was delayed throughout the task. During prolonged and repeatable balance perturbation, an ongoing postural adaptation process occurs. When the effects of the perturbation become predictable, the CNS scales the level of muscle activity to counteracting the destabilizing effects of the perturbations. Furthermore, the CNS tunes the kinematics and the kinetic responses optimally by slightly delaying the onset of the body forward rotation, maintaining unchanged the time-pattern of postural muscle activation.
Department of Electrical, Computer and Biomedical Engineering, University of Pavia, Via Ferrata 5, I-27100 Pavia, Italy. Electronic address: micaela.schmid@unipv.it.
Micaela
M
Schmid
Fondazione Salvatore Maugeri (IRCCS), Scientific Institute of Pavia, Via Salvatore Maugeri 10, I-27100 Pavia, Italy. Electronic address: sozzi_stefania@hotmail.it.
Stefania
S
Sozzi
D000222:Adaptation, Physiological; D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance; D055815:Young Adult
Continuous perturbation; Dynamic balance control; Muscle activity time pattern; Postural adaptation process