VII. EXPERIMENTAL RESULTS, SCHEMES AND DATA NORMALIZATION The effective charges α$_{g}$$_{1}$ and α$_{F}$$_{3}$ shown in Figs. 1 and 2 are extracted in Ref. [39] following the prescription of Grunberg. [9] Data on the spin structure function g$_{1}$ , from JLab [52] are used to form α$_{g}$$_{1}$ . CCFR data on the structure function F$_{3}$ [53] are used to form α$_{F}$$_{3}$ , which is then related to α$_{g}$$_{1}$ using a CSR. The GDH and Bjorken sum rules constrain, respectively, the small [40] and large [12] Q 2 behavior of the integral of g$_{1}$ and provide a description of α$_{g}$$_{1}$ over a large domain. We note that the works of [9] and [10] pertain to the UV domain, whereas Ref. [39] extends them to the IR region based on the analytical behavior of the coupling. The effective charge α$_{g}$$_{1}$ is found to be approximately scale invariant in the IR domain, in agreement with an IR fixed point behavior. [29] The shape of the coupling α$_{g}$$_{1}$ agrees with other predictions of the running coupling α$_{s}$ at small Q $^{2}$, including lattice QCD, [38] the Schwinger-Dyson formalism, [28, 44] and the coupling of a constituent quark model which is consistent with hadron spectroscopy. [54] We point out that the essential difference between these running couplings is their value at Q 2 = 0: if normalized to the same point at Q 2 = 0, their Q 2 dependences agree within their relative uncertainties. [39] The continuous band in Fig. 1 for α$_{g}$$_{1}$ is computed with the Bjorken sum rule using the relation between α$_{g}$$_{1}$ and α$_{MS}$ . [10, 39] The pQCD leading-twist expression of the Bjorken sum up to third order in α$_{MS}$ is used to estimate the Bjorken sum. The sum rule is then used to extract α$_{g}$$_{1}$ at large Q. In the pQCD expression of the Bjorken sum rule, α$_{MS}$ is retained up to second order in β (i.e. up to β$_{2}$ ). The uncertainty in the band comes from the uncertainty on Λ$_{MS}$ = 0 . 37 +0 . 04 − 0 07 and the truncation of the series. [55] Although the effective coupling α$_{g}$$_{1}$ ( Q $^{2}$) has specific features of deep inelastic lepton- proton scattering, it nevertheless appears to closely mimic the shape and magnitude of the AdS/QCD coupling near the transition region Q ≃ Q$_{0}$ . In particular, it illustrates how one can have a coupling which flows analytically from the IR strong coupling domain with an IR fixed point to the UV domain controlled by pQCD. [57] The value of α AdS s ( Q ) at Q = 0 was not determined by our holographic approach. [58] It is also well known that even in the pQCD domain the value of running coupling is significantly scheme dependent when the momentum transfer becomes small. It is thus reasonable to assume that such differences propagate in the IR domain and consequently the IR value of 16