Axial coupling from matching constituent quark model to QCD
  The axial-vector coupling $g_A$ of a constituent quark is estimated from matching the constituent quark model to the operator product expansion in QCD in the limit of large number of colours under some assumptions. The obtained relation is $g_A\simeq\sqrt{7/11}\approx0.80$, which is in agreement with the existing model estimates. 
S.S. Afonin