At high loading rates, the development of adiabatic shear bands in metals is conventionally attributed to the strong interactions induced by viscoplastic dissipation within the bands and thermal softening effects. The rheological equation proposed by Johnson and Cook takes both viscoplastic hardening and thermal softening into account. The present paper reviews and includes this equation into a thermodynamic framework in order to analyse the energy impacts of thermal softening. Indeed this latter implies the existence of a ther-momechanical coupling source, probably non-negligible and which must be considered when estimating temperature variations induced by shear band development.