  New strong gauge interactions remain a viable source for the electroweak
symmetry breaking. However, addressing the generation of fermion masses remains
a challenge. A basic observable which provides stringent constraints on the
flavor extensions of Technicolor-type models is the decay rate of the Z boson
into a bbbar-pair. In this paper we provide a general framework to evaluate the
resulting constraints on the technicolor theory level taking into account the
contributions from the vector and axial vector mesons and discuss the
consequences for phenomenology.
