  The idea of applying isoperimetric functions to group theory is due to
M.Gromov. We introduce the concept of a ``bicombing of narrow shape'' which
generalizes the usual notion of bicombing. Our bicombing is related to but
different from the combings defined by M. Bridson. If the Cayley graph of a
group with respect to a given set of generators admits a bicombing of narrow
shape then the group is finitely presented and satisfies a sub-exponential
isoperimetric inequality, as well as a polynomial isodiametric inequality. We
give an infinite class of examples which are not bicombable in the usual sense
but admit bicombings of narrow shape.
