These words for bow (βιός) and life (βίος) were pronounced differently because of accentuation.  However, when written down, they looked identical (ΒΙΟΣ / ΒΙΟΣ).  Heraclitus plays on this written ambiguity in this fragment.  This fragment shows that Heraclitus did not compose his book as a set of spoken statements; his book is clearly a written one.  This fragment only has its force if it were written down.