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Adam Siemienski

Publications and source records attributed to Adam Siemienski.

3 recordsLinked to original sources

Can all muscular load sharing patterns be regarded as optimal in some sense?

Muscles crossing a joint usually outnumber its degrees of freedom, which renders the motor system underdetermined. Typically, optimization laws are postulated to cope with this redundancy. A natural question then arises whether all muscular load sharing patterns can be regarded as results of optimization. To answer it, we propose a method of constructing an objective function whose minimization yields a given load sharing pattern. We give necessary conditions for this construction to be feasible and investigate its uniqueness. For linear load sharing patterns the Crowninshield and Brand objective function is reproduced, nonlinear ones require a more general formula.

q-bio.TO

Direct solution of the inverse optimization problem of load sharing between muscles

In the context the statically indeterminate muscular load sharing problem considered in biomechanics of the musculoskeletal system, a method is suggested of constructing an additively separable and homogenous cost function based on a solution to a linearly constrained optimization problem involving this cost function. The construction makes use of the Koenigs solution of Schroeder's functional equation.

math.OC

Fatigue independent amplitude-frequency correlations in EMG signals

In order to assess fatigue independent amplitude-frequency correlations in EMG signals we asked nineteen male subjects to perform a series of isometric muscular contractions by extensors of the knee joint. Different amplitudes of the signal were due to randomly varying both the joint moment and the overall amplification factor of the EMG apparatus. Mean and median frequency, RMS and mean absolute value were calculated for every combination of joint moment and amplification at the original sampling rate of 5 kHz and at several simulated lower sampling rates. Negative Spearman and Kendall amplitude-frequency correlation coefficients were found, and they were more pronounced at high sampling rates.

physics.data-an