The purpose of this study was to determine the relative influence of age-related changes in neural, muscular and tendinous properties on the ability to recovery balance from a forward leaning position using the ankle strategy. A computer simulation was developed selleck inhibitor which consisted of an inverted pendulum with one rotational degree of freedom controlled by two muscles representing the ankle joint plantar flexor (PF) and dorsi flexor (DF) muscle groups. Model parameter values were adjusted so that the isometric torque-angle relation was in agreement with experimental
ankle joint torque-angle curves From the literature. Muscle excitation was adjusted to match an experimentally determined maximum recoverable lean angle (MRLA) of 7.2 degrees (baseline condition). The effect of 20% alterations to maximum isometric force, optimum muscle fibre length, Selleck LCL161 maximum shortening velocity, tendon stiffness, reaction time delay (RTD), activation time constant and the maximum excitation of the PF muscles, and Maximum excitation of the DF muscles (co-activation) on MRLA was then assessed.The parameters that had the greatest influence on MRLA were maximum isometric force, the maximum excitation of the ankle joint PFs and RTD, which, respectively, resulted in 19.0%, 17.8% and 4.6% reductions in MRLA. Individual changes to other parameters influenced MRL-A by less
than 1.9%. When selected parameter values were adjusted in accordance with age-related changes reported in the literature, MRLA was reduced to 5.3 degrees, a value in relative agreement with experimental values reported in the literature (4.6 +/- 1.8 degrees). In general, these results suggest that MRLA is most sensitive to PF muscle mass and the ability to maximally activate the Us, and that the combined effect of all multiple changes in neural, muscular and tendinous parameters reported to occur with aging
can have a profound effect on the ability to recover balance from a forward fall using the ankle strategy. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.”
“A method for detailed description of the time-frequency characteristics of electroencephalogram during induction of anesthesia is proposed. The method, based on averaging of time-normalized smoothed pseudo-Wigner-Ville distributions, is applied to data recorded from nine patients undergoing propofol anesthesia. An extensive representation of the frequency progression pattern related to the induction of anesthesia is given and the time-frequency characteristics that are consistent/not consistent between patients are determined. It is also illustrated how four different clinical end-points, generally used in the assessment of the depth of anesthesia, can be related to different phases of the frequency progression pattern.