"Aging" is what costs you flexibility and speed. If you reverse aging, you'll maintain your flexibility and speed.
Moreover, aren't you assuming that we couldn't possibly manage loss of flexibility? Even if most people are inflexible because they've aged, this doesn't prohibit them from having a base level of flexibility and thus find a workaround for whatever limitation you're imagining this imposes.
Moreover, aren't you assuming that we couldn't possibly manage loss of flexibility? Even if most people are inflexible because they've aged, this doesn't prohibit them from having a base level of flexibility and thus find a workaround for whatever limitation you're imagining this imposes.