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