  We present recent results on the Bjorken and the generalized forward spin
polarizability sum rules from Jefferson Lab Hall A and CLAS experiments,
focusing on the low $Q^2$ part of the measurements. We then discuss the
comparison of these results with Chiral Perturbation theory calculations. In
the second part of this paper, we show how the Bjorken sum rule with its
connection to the Gerasimov-Drell-Hearn sum, allows us to conveniently define
an effective coupling for the strong force at all distances.
