Half of one oh eight

Though some may say I'm fifty-four
to that I can't relate.
I prefer to think that I'm 
one half of one oh eight.

My bones may creak and groan as I
ascend another rung,
my mind, however, stubbornly,
remains forever young.

Six months from now my body may
insist that I recline,
but in my head I'll dance with joy...
one half of one oh nine!