ReplayQuick Play
About
Snippet
There
are
two
kinds
of
fibers
in
our
muscles,
red
and
white.
When
an
athlete
trains
for
long
distance
running,
he
or
she
builds
more
red
muscle
fibers
than
white
muscle
fibers
in
his
calf
muscles.
A
sprinter
has
more
white
muscles.
If
you
retrain
a
marathon
runner
to
be
a
sprinter,
most
of
the
muscle
fibers
will
convert
to
white
muscles.
The replay is still saving.