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Europa Medicophysica 2000 December;35(4):205-19


language: English

Physical exercise in the elderly: its effects on the motor and endocrine system

Capodaglio P. 1, Narici M. V. 2, Rutherford O. M. 3, Sartorio A. 4

1 Centre for the Study of Motor Activities (CSAM) Institute of Pavia, “S. Maugeri” Foundation, IRCCS; 2 Department of Exercise and Sport Science, Manchester Metropolitan University, Alsager, UK; 3 Imperial College School of Medicine, London, UK; 4 Laboratory of Endocrinological Research (LSRE), Italian Auxologic Institute, IRCCS, Milan and Metabolic Diseases Unit III, Italian Auxologic Institute, IRCCS, Piancavallo (VB), Italy


Ageing is asso­ciat­ed ­with ­reduced max­i­mal aero­bic pow­er, mus­cle ­strength and pow­er; name­ly, ­reduced fit­ness. Based on the exist­ing evi­dence con­cern­ing exer­cise pre­scrip­tion for ­healthy ­adults, in 1990, the American College of Sports Medicine (­ACSM) ­made the fol­low­ing rec­om­men­da­tions: fre­quen­cy of train­ing: 3-5 ­days/­week, inten­sity: 60-90% HRmax, or 50-85% ˙VO2max, dura­tion: 20-60 min of con­tin­u­ous aero­bic activ­ity ­with involve­ment of ­large mus­cle ­groups. However, the tar­get of improv­ing/main­tain­ing phys­i­cal fit­ness is inap­pro­pri­ate for the ­whole eld­er­ly pop­u­la­tion, ­which ­includes the ­frail. In ­these sub­jects, the achieve­ment of a bet­ter ­health stat­us is cer­tain­ly the pri­mary ­goal, as recent­ly stat­ed by the 1996 Heidelberg guide­lines. Physical activ­ity ­should be pre­scribed on the ­basis of an indi­vid­u­al ­health/fit­ness gra­di­ent ­with dif­fer­ent ­goals. Lower lev­els of phys­i­cal activ­ity ­than ­those rec­om­mend­ed by the ­ACSM may ­reduce the ­risk for cer­tain chron­ic degen­er­a­tive dis­eas­es and yet may not be of suf­fi­cient quan­tity or qual­ity to ­improve ˙VO2max. In the ­wake of ­these con­sid­er­a­tions and the inclu­sion of the improve­ment/main­tain­ing of ­health stat­us ­among the ­goals of exer­cise pre­scrip­tion in the eld­er­ly pop­u­la­tion, in 1991, the ­ACSM low­ered the rec­om­mend­ed exer­cise inten­sity to as low as 35-40% ˙VO2max. One of the ­most crit­i­cal con­se­quenc­es of age­ing of the ­motor ­system is mus­cle weak­ness. Several caus­es may be ­held respon­sible for ­this phe­nom­e­non; ­among ­these sar­co­pe­nia is, prob­ably, the ­most com­mon. The lat­ter ­involves ­both a ­decrease in mus­cle ­fibre ­size and num­ber. However, atro­phy can­not ­alone entire­ly ­account for ­senile mus­cle weak­ness. As a mat­ter of ­fact, the max­i­mum ­force ­that may be gen­er­at­ed per mus­cle ­cross-sec­tion­al ­area (F/CSA) is low­er in eld­er­ly sub­jects. This phe­nom­e­non sug­gests ­that mus­cu­lar or neu­ral fac­tors, or ­more like­ly ­both, are ­involved. Another com­mon ­cause for the ­decrease in F/CSA is mus­cle acti­va­tion. Recent ­reports ­show incom­plete quad­ri­ceps mus­cle acti­va­tion in ­very old (80+) men and wom­en. Since ­almost com­plete (95%) mus­cle acti­va­tion was ­found in a pop­u­la­tion of sub­jects ~70 ­year old, it ­seems ­that acti­va­tion capac­ity rap­id­ly ­falls ­beyond the 7th ­decade. Therefore, tak­en togeth­er, the ­above neu­ral fac­tors may ­account for ­large ­part of the ­decrease in ­force ­with age­ing. Hormonal chang­es in them­selves are not the sim­ple expla­na­tion for all of the chang­es asso­ciat­ed ­with age­ing. Studying the ­effects of ­strength train­ing on the endo­crine ­system is com­pli­cat­ed by a varie­ty of fac­tors relat­ed to ­both the exer­cise chal­lenge ­itself and the accu­rate meas­ure­ments of hor­mones. The meas­ure­ment of hor­mo­nal chang­es is com­pli­cat­ed by the man­ner in ­which ­they are ­released, trans­port­ed and inter­act ­with the tar­get tis­sue. Many hor­mones are ­released in a pul­sa­tile man­ner ­with super­im­posed diur­nal, month­ly, and sea­son­al ­rhythms. They ­often ­exist in dif­fer­ent molec­u­lar ­weight frac­tions and are fre­quent­ly trans­port­ed in a ­bound ­form. From the ­work ­that has ­been car­ried out in young­er peo­ple it ­would ­appear, ­that if suf­fi­cient ­high resis­tance exer­cise is car­ried out, ­then the ­acute hor­mo­nal ­response is not qual­ita­tive­ly dif­fer­ent to ­that fol­low­ing a ­bout of endu­rance exer­cise. Exercise train­ing pro­grams ­have ­been sug­gest­ed as pos­sible coun­ter­meas­ures ­against invo­lu­tion­al ­bone ­loss, ­being ­able to pre­vent or ­reverse ­almost 1% of ­bone ­loss per ­year in ­both lum­bar ­spine and femo­ral ­neck for ­both pre- and post­men­o­pau­sal wom­en. As far as eld­er­ly peo­ple are con­cerned, it ­appears ­that ­strength train­ing may ­have a ­more ben­e­fi­cial ­effect ­than aero­bic train­ing on BMD, espe­cial­ly in post­men­o­pau­sal wom­en, ­although ­some evi­dence sug­gests ­that ­also aero­bic train­ing may ­improve BMD in the eld­er­ly. To ­date, the ­effect of phys­i­cal activ­ity on ­bone turn­over has ­received lim­it­ed atten­tion ­despite the ­strict depen­dence of ­bone ­mass on the bal­ance ­between ­bone for­ma­tion and ­bone resorp­tion. The equi­lib­ri­um ­between ­these two com­po­nents of ­bone turn­over is cru­cial for ­bone ­mass and BMD, ­since ­bone ­loss, or ­increase, ­results ­from an ­uncoupling of ­bone for­ma­tion and ­bone resorp­tion.
During the ­last few ­years ­there has ­been a rap­id devel­op­ment of reli­able meth­ods to meas­ure bio­chem­i­cal mark­ers of ­bone metab­olism. Since ­these mark­ers ­reflect the cel­lu­lar ­events, ­they may pro­vide new oppor­tu­nities to elu­ci­date the ­effects of phys­i­cal exer­cise on ­bone metab­olism.

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