  In this paper we study global Poincare inequalities on balls in a large class
of sub-Riemannian manifolds satisfying the generalized curvature dimension
inequality introduced by F.Baudoin and N.Garofalo. As a corollary, we prove the
uniqueness of solutions for the subelliptic heat equation. Our results apply in
particular to CR Sasakian manifolds with Tanaka-Webster-Ricci curvature bounded
from below and Carnot groups of step two.
