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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)
Indexed/Abstracted in: CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
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Europa Medicophysica 2004 September;40(3):239-46


language: English


Bonaiuti D.

Unit of Phyical Medicine and Rehabilitation S. Gerardo General Hospital, Monza (Milan), Italy


In ­this ­issue, we ­would com­plete the con­clu­sions of the system­at­ic revi­sion ­with the ­results ­from the ­major clin­i­cal and experi­men­tal stud­ies. First of all, we out­line ­that the use of ­bone min­er­al den­sity is con­tro­ver­sial and ­opposed of the ­major stud­ies in the ­field ­that ­show ­that the ­bone den­sity is ­only one of the fac­tors ­which ­describe ­bone resis­tance, and not the ­bone qual­ity. In ­fact, ­often, a dra­mat­ic vari­a­tion of ­bone ­strength is ­linked to the ­fact ­that the new­ly ­bone is locat­ed in the ­only in the sur­fac­es ­where mechan­i­cal ­stress is great­est and ­this ­doesn’t ­change com­plete­ly the den­sity. To ­study the opti­mal exer­cis­es pro­gram we ­have to remem­ber ­that the ­ideal tim­ing in the remod­el­ling ­unit of the ­bone was esti­mat­ed at 4-6 ­months: there­fore any treat­ment ­which has the aim of pre­vent­ing ­bone ­loss ­should ­last at ­least 2-3 ­times ­this peri­od to ­ensure ­that the reg­is­tered ­effect on ­bone den­sity is eval­u­at­ed in a peri­od of bal­ance. According to Frost, the ­strength of the ­bone is deter­mined by 4 fac­tors: the mechan­i­cal prop­er­ty char­ac­ter­is­tic of ­bony tis­sue, the ­amount of ­micro dam­age ­from ­fatigue, ­bone ­mass fac­tors (­amount and ­type of ­bone in the ­bone) and the ­size and shap­er of the ­bone (archi­tec­tu­ral fac­tors). Moreover, it is ­very impor­tant the ­role of mus­cu­lar ­strength on the ­bone: the mus­cles ­work ­like a lev­er in ­such a man­ner ­that to ­move eve­ry ­kilo of ­body ­weight, the mus­cu­lar ­force is usu­al­ly ­over 2 kg. This ­explains why ­strong mus­cles are usu­al­ly asso­ciat­ed ­with ­strong ­bones. About the spe­cif­ic ­role of the ­strain on the ­bone, ­from stud­ies of the ­past 10 ­years ­there ­seems to be ­more pre­cise and use­ful infor­ma­tion for our quer­ies: new for­ma­tion of ­bone ­took ­place in rab­bits ­only ­with dynam­ic stim­u­li and not stat­ic, and it is ­very impor­tant ­also the fre­quen­cy of the stim­u­lus and the ­speed. Moreover, ­some ­authors ­have ­shown ­that the stim­u­li of oste­goe­ne­sis ­depends on the ­fluid ­shear stress­es ­though the lac­u­nar-can­a­lic­u­lar net­work ­system. So: exer­cis­es at ­high ­impact ­which can pro­duce sig­nif­i­cant def­or­ma­tion of the ­bone ­matrix, bet­ter car­ry the ­fluid ­through the can­a­lic­u­lar net­work and fur­ther­more the ­strains ­applied at ­high fre­quen­cy stim­u­late in a effec­tive man­ner oste­o­gen­e­sis. Therefore, the mechan­i­cal ­strain nec­es­sary to ­begin oste­o­gen­e­sis decreas­es ­with the ­increase of the fre­quen­cy of the ­strain. Rubin and Lanyon ­have ­shown ­that the pro­lon­ga­tion of the stim­u­la­tion ­with ­strain the oste­o­gen­ic ­response did non ­increase if the reg­i­men is pro­longed ­more. In ­fact, Turner dem­on­strat­ed ­that the ­bone ­presents a phe­nom­e­non of desen­sit­isa­tion fol­low­ing a pro­longed ­strain stim­u­lus. He pro­posed the oste­o­gen­ic ­index of exer­cis­es ­like the oste­o­gen­ic ­response to exer­cise ­which ­could be ­increased in a reg­i­men of exer­cis­es ­which fore­see ­also a peri­od of ­rest ­between ­brief ses­sions of sig­nif­i­cant ­strain. So, con­cern­ing the ­effects of exer­cis­es, the stim­u­lus pro­duced by the ­strain ­must be ­such ­that it ­exceeds a thresh­old of a min­i­mum effec­tive stim­u­lus, ­must be ­applied in a inter­mit­tent and dynam­ic man­ner, ­should pro­duce a stim­u­lus ­which is dis­trib­ut­ed dif­fer­ent­ly to the ­norm, ­should be ­applied ­with ­high ­speed and few rep­e­ti­tions.

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