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A Journal on Physical Medicine and Rehabilitation after Pathological Events

Official Journal of the Italian Society of Physical and Rehabilitation Medicine (SIMFER), European Society of Physical and Rehabilitation Medicine (ESPRM), European Union of Medical Specialists - Physical and Rehabilitation Medicine Section (UEMS-PRM), Mediterranean Forum of Physical and Rehabilitation Medicine (MFPRM), Hellenic Society of Physical and Rehabilitation Medicine (EEFIAP)
In association with International Society of Physical and Rehabilitation Medicine (ISPRM)
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Europa Medicophysica 2004 June;40(2):59-65


language: English

The stabilometric evaluation of the erect stance. Energy-based optimal control in a numerical model

Pascolo P. B. 1, 2, Saccavini M. 3

1 Department of Civil Engineering University of Udine, Udine, Italy 2 Department of Bioengineering, CISM, Udine, Italy 3 Department of Biomechanics and Occupational Therapy Department of Rehabilitation Medicine Institute of Physical and Rehabilitative Medicine, Udine, Italy


Aim. This ­paper pro­pos­es an anthro­po­mor­phic mod­el devel­oped in a vir­tu­al con­text, use­ful to sim­u­late the main­te­nance of the ­erect ­stance. Such a mod­el can be ­built ­through a suit­able soft­ware ­which can iden­ti­fy the geom­e­try of the artic­u­lar ­parts and ­place mechan­i­cal con­straints (e.g. ­joints, spher­i­cal ­links, etc.) ­between the sin­gle ele­ments.
Methods. Our ­approach can be ­described as the assem­bly of rig­id ­parts ­linked at the ­joints. The con­trol is giv­en by inter­nal ­torques at the ­joints and driv­en by strat­e­gy for the bal­ance ­aimed to the ­least ­amount of ­total mus­cu­lar ener­gy ­spent. The anthro­po­mor­phic mod­el pro­posed under­lines and ­solves the typ­i­cal prob­lems of a ­system char­ac­ter­ized by a mul­ti­ple num­ber of ­degree of free­dom ­placed in ­erect ­stance and per­turbed by phe­nom­e­na of endog­e­nous and exog­e­nous ­nature. This mod­el is devel­oped via the ­coupling of 2 sep­ar­ate bi-dimen­sion­al mod­els, one rep­re­sent­ing the sag­it­tal ­plane and the oth­er the fron­tal ­plane. The numer­i­cal ­tests ­were val­i­dat­ed ­through experi­men­tal ­tests in a ­group of ­healthy vol­un­teers. For ­this pur­pose we ­employed a sta­bil­o­met­ric plat­form (­force-­plate) to ­record the stat­o­kin­e­si­gram (SKG) on the ­rest sur­face.
Results. The ­shapes of the sta­bil­o­met­ric ­plots ­show a ­good spa­tial sim­i­lar­ity ­between the experi­men­tal and sim­u­lat­ed SKG. Both SKGs ­present a ­good ­range in the fron­tal ­plane ­with con­cen­tra­tion of ­points in ­some are­as (or attrac­tors) in the experi­men­tal SKG, but not in the sim­u­lat­ed one. The ­tests ­also ­showed a pos­tu­ral oscil­la­tion at low fre­quen­cy (≈ 0.02Hz), prob­ably due to the dif­fe­ren­tial tir­ed­ness of ­groups of mus­cles or ­because of a ­delayed ­action of the neu­ro­log­i­cal con­trol.
Conclusion. On the numer­i­cal sim­u­la­tions, we ­claim the suit­abil­ity of the antrop­o­mor­phic mod­el for a gen­er­al descrip­tion of the main­te­nance of the ­erect ­stance. Despite the sim­plifi­ca­tion, ­with our ­approach it is pos­sible to sim­u­late ­some of the ­main char­ac­ter­is­tics of the pos­tu­ral act. In par­tic­u­lar, the ­length and the are­as of the sim­u­lat­ed SKG’s are com­par­able ­with ­those of the experi­men­tal ­tests.

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