oms ▁until ▁it ▁is ▁severe ▁and ▁is ▁often ▁un recogn ized . ▁ ▁C aus es ▁ ▁There ▁are ▁many ▁proposed ▁causes ▁of ▁s arc open ia ▁and ▁it ▁is ▁likely ▁the ▁result ▁of ▁multiple ▁interact ing ▁factors . ▁Under standing ▁of ▁the ▁causes ▁of ▁s arc open ia ▁is ▁incomplete , ▁however ▁changes ▁in ▁h orm ones , ▁imm ob ility , ▁age - related ▁mus cle ▁changes , ▁nut r ition ▁and ▁ne uro de gener ative ▁changes ▁have ▁all ▁been ▁recognized ▁as ▁potential ▁caus ative ▁factors . ▁▁ ▁The ▁degree ▁of ▁s arc open ia ▁is ▁determined ▁by ▁two ▁factors : ▁initial ▁amount ▁of ▁mus cle ▁mass ▁and ▁rate ▁at ▁which ▁mus cle ▁mass ▁decl ines . ▁Due ▁to ▁variations ▁in ▁these ▁factors ▁across ▁the ▁population , ▁the ▁rate ▁of ▁pro gression ▁and ▁the ▁threshold ▁at ▁which ▁mus cle ▁loss ▁becomes ▁apparent ▁is ▁variable . ▁Im m ob ility ▁dram atically ▁increases ▁the ▁rate ▁of ▁mus cle ▁loss , ▁even ▁in ▁younger ▁people . ▁Other ▁factors ▁that ▁can ▁increase ▁rate ▁of ▁pro gression ▁of ▁s arc open ia ▁include ▁decre ased ▁nut ri ent ▁int ake , ▁low ▁physical ▁activity , ▁or ▁chron ic ▁disease . ▁Additionally , ▁ep ide mi ological ▁research ▁has ▁indicated ▁that ▁early ▁environmental ▁influ ences ▁may ▁have ▁long - term ▁effects ▁on ▁mus cle ▁health . ▁For ▁example , ▁low ▁birth ▁weight , ▁a ▁marker ▁of ▁a ▁poor ▁early ▁environment , ▁is ▁associated ▁with ▁reduced ▁mus cle ▁mass ▁and ▁strength ▁in ▁adult ▁life . ▁