Formation and evolution of stars and substellar objects (brown dwarfs and planets) are described by theoretical models. Observers can use these models to determine several parameters of an object taken observables. However, these models still need to be properly tested and calibrated with observations. The purpose of this thesis is to bring some constrain to stellar and substellar formation and evolutionary models. I combined the high contrast imaging and radial-velocity methods to study substellar objects at wide separation and stellar systems of very low mass stars. This combination of techniques allow to determine the dynamical masses of the objects inside a system. Thanks to the high contrast imaging, photons coming directly from the objects can be collected which allowed me to characterize the atmosphere of substellar objects with a spectral analyze. These informations allow to put some constrain to evolutionary models of substellar objects.