The transport reduction in Internal Transport Barrier (ITB) regimes is often correlated with some turbulence suppression. The E¥B flow shearing rate is considered to be partially responsible for the decorrelation of the turbulence associated with the ion temperature gradient (ITG) driven modes. However, there are other possible mechanisms, associated with magnetic shear, s, which could explain the onset and characterisation of the ITBs. From the analysis of various JET discharges having different q profiles (produced by use of LHCD with different timings) and different input momentum (obtained by varying the neutral beam torque), in principle it would be possible to separate the role played by the magnetic shear and the shearing rate. In practice, the difficulties related to the reproducibility of experimental conditions and the data analysis are strongly reducing the above described possibility. Two types of barriers are usually found in JET expriments: barriers at around half radius and more external ones, which are often correlated with some rational q surface. However, by using a database of selected discharges with available q profiles from EFIT equilibrium reconstruction constrained by Motional Stark Effect (MSE) diagnostic data and limiting the analysis to the inner type barriers, a clear correlation has been found between three different experimental parameters. The location of the foot of the barrier (defined as the position when a critical Ti gradient is achieved) has been compared in space and time with the location of the s=0 curve. It turns that these two quantities seem to coincide within experimental errors. In addition, the ratio between the E¥B flow shearing rate, ws, and the ITG linear growth rate, gh, has also been compared with the previous two quantities. Again, regions with ws/ghi >1 are well correlated with the position of both the s=0 curve and the foot of the barrier. These observed correlations between the magnetic shear, the shearing rate behaviour and the onset of the ITB are tentatively compared with the predictions of theoretical models where the ITG modes are responsible for the anomalous energy transport.