Different strength hypotheses in lifetime predictions of static and dynamic loaded rubber parts are used in research and industry. A strength hypotheses gives the correlation between the strains and stresses and the fatigue in the rubber material. In the literature strength hypotheses criteria for elastomers were used more or less successfully in different applications. A new strength hypotheses is proposed. An investigation based on lifetime tests shows the potentials and limits of different hypotheses. The Woehler approach and the approach based on fracture mechanics were compared.