简介：Naturaladultagingisassociatedwithmanyfunctionalimpairmentsofthehumanneuromuscularsystem.Oneofthemoreobservablealterationsisthelossofcontractilemusclemass,termedsarcopenia.Thelossofmusclemassoccursprimarilyduetoaprogressivelossofviablemotorunits,andaccompanyingatrophyofremainingmusclefibers.Notonlydoesthelossofmusclemasscontributetoimpairedfunctioninoldage,butalterationsinfibertypeandmyosinheavychainisoformexpressionalsocontributetoweaker,slower,andlesspowerfulcontractingmuscles.Thisreviewwillfocusonmotorunitlossassociatedwithnaturaladultaging,age-relatedfatigability,andtheage-relateddifferencesinstrengthacrosscontractilemuscleactions.

简介：Background:Thisprospectivestudyexploredtheeffectsofendurancerunning(ER)inminimalversusstandardrunningshoesonthefoot'ssuperficiallayerintrinsicmusclesandthefunctionofthelongitudinalarch.Ourhypothesiswasthatrunninginminimalshoeswouldcausehypertrophyinthesemusclesandleadtohigher,stronger,stifferarches.Methods:Thehypothesiswastestedusingasampleof33healthyrunnersrandomizedintotwogroups,acontrolgroupshodintraditionalrunningfootwearandanexperimentalgroupshodinminimalsupportfootwear,whosefeetwerescannedinanMRIbeforeandaftera12-weektrainingregime.Runningkinematicsaswellasarchstiffnessandheightwerealsoassessedbeforeandafterthetreatmentperiod.Results:Analysisofanatomicalcross-sectionalareasandmusclevolumesindicatethattheflexordigitommbrevismusclebecamelargerinbothgroupsby11%and21%,respectively,butonlytheminimallyshodrunnershadsignificantarealandvolumetricincreasesoftheabductordigitiminimiof18%and22%,respectively,andsignificantlyincreasedlongitudinalarchstiffness(60%).Conclusion:Theseresultssuggestthatendurancerunninginminimalsupportfootwearwith4mmoffsetorlessmakesgreateruseofthespringlikefunctionofthelongitudinalarch,thusleadingtogreaterdemandsontheintrinsicmusclesthatsupportthearch,therebystrengtheningthefoot.

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