▁Path oph ys i ology ▁There ▁are ▁multiple ▁theories ▁proposed ▁to ▁explain ▁the ▁mechan isms ▁of ▁mus cle ▁changes ▁of ▁s arc open ia ▁including ▁changes ▁in ▁satellite ▁cell ▁rec ruit ment , ▁changes ▁in ▁an abol ic ▁sign alling , ▁protein ▁ox id ation , ▁infl amm ation , ▁and ▁development al ▁factors . ▁The ▁path olog ic ▁changes ▁of ▁s arc open ia ▁include ▁a ▁reduction ▁in ▁mus cle ▁t issue ▁quality ▁as ▁reflected ▁in ▁the ▁replacement ▁of ▁mus cle ▁fib ers ▁with ▁fat , ▁an ▁increase ▁in ▁fib ros is , ▁changes ▁in ▁mus cle ▁met abol ism , ▁ox id ative ▁stress , ▁and ▁deg ener ation ▁of ▁the ▁neur om us cular ▁j unction . ▁▁ ▁The ▁distribution ▁of ▁mus cle ▁fib ers ▁types ▁also ▁changes ▁in ▁s arc open ic ▁mus cle ▁causing ▁a ▁decrease ▁in ▁type ▁II ▁mus cle ▁fib ers , ▁or ▁" fast ▁tw itch ," ▁or ▁with ▁little ▁to ▁no ▁decrease ▁in ▁or ▁type ▁I ▁mus cle ▁fib ers , ▁or ▁" slow - tw itch " ▁mus cle ▁fib ers . ▁De iner v ated ▁type ▁II ▁fib ers ▁are ▁often ▁converted ▁to ▁type ▁I ▁fib ers ▁by ▁re inner v ation ▁by ▁slow ▁type ▁I ▁fi ber ▁motor ▁n erves . ▁ ▁The ▁failure ▁to ▁activ ate ▁satellite ▁cells ▁upon ▁injury ▁or ▁exercise ▁is ▁also ▁thought ▁to ▁contribute ▁to ▁the ▁path oph ys i ology ▁of ▁s arc open ia . ▁Additionally , ▁ox id ized ▁prote ins ▁can ▁lead ▁to