Mutations in the voltage-gated sodium channel hNa_v1.4 have been correlated to various muscle diseases, such as Paramyotonia Congenita (PC), a disease clinically characterized by attacks of muscle stiffness mainly triggered by exposure to cold. Mutations causing PC share a common gating defect: slowed inactivation from the open state. This mainly accounts for the disease symptoms. Nevertheless, the origin of the temperature dependence and the implication of other possible gating alterations for PC are still contradictorily discussed. Here we investigated the gating of WT and R1448H, a typical PC mutation, in a broad temperature range by performing whole-cell patch-clamp experiments on HEK-293 cells, stably expressing hNa_v1.4. To better understand disease patho-physiology and to allow incorporation in more general systemic muscle models, we tested different gating schemes considering all gating transitions altered by PC mutations and fitted these models to our measurements. Our preferred model consisted of a series of 4 closed states, one open state and three parallel inactivated states. To account for the second time constant in fast inactivation, especially at low temperatures, a two step inactivation process was introduced. Rate constants were obtained by a simultaneous fit to several different data sets measured on the same cell: 6 current traces of an activation protocol, a steady-state inactivation curve, recovery curves at 3 different potentials and entry into fast inactivation curves at 4 different potentials. To gain inside in the temperature dependency of WT and R1448H sodium channel gating, we calculated the rate constants for measurements between 10 and 25°C. In summary, we present a model that describes the gating of WT and R1448H sodium channels in a broad temperature range. Simulated time constants associated with fast inactivation are in excellent agreement with the measurements. For WT, the alignment of the time constants associated with fast inactivation is represented by a bell shaped curve with a maximum around –80 mV. The analogous alignment for R1448H is a curve with two maxima. We propose that accelerated closed-state inactivation of R1448H influences the time constants of fast inactivation in the range of -60 to -40 mV. Channels which deactivate in this voltage range have a higher probability to go to the closed-inactivated state than back to the open state. Our results suggest that the position of DIV-S4 is essential for inactivation from both closed and opened states. R1448H might shift the voltage dependent availability of the inactivation particle binding site to hyperpolarized potentials. Therefore a mild depolarization facilitates inactivation from closed states, but impairs inactivation from open states at further depolarized potentials. As a consequence, a small depolarization leads to an increased sodium channel inactivation and leads to inexcitability.