burn out .
lack of good recovery ,rest ,nutrition ,habits ,attitude,
weather etc will lead to burn out.
anything that causes stress to the many various biological
pathways in body can eventually lead to it by whatever system is flagging .
nervous system being the one that needs the most rest
and hardest to get back .
but others like hormones , metabolism ,etc .
and this is in short term.
if persists and damage done then done as an elite .
in long term could call it "old age ".
ways to avoid "burn out" exogenously methods
and also to return to past performances if burn out
persists .