  We consider the QCD string as an effective string, whose action describes
long-range stringy fluctuations. The leading infrared contribution to the
ground state energy is given by the Alvarez-Arvis formula, usually derived
using the Nambu-Goto action. Here we rederive it by a saddle point calculation
using the Polyakov formulation of the free string, where the world sheet metric
and the target space coordinates are treated as independent variables. The next
order relevant in the infrared term in the effective action is the extrinsic
curvature term. We show that the spectrum does not change order by order in the
inverse string length, but may change at intermediate distances.
