In a dynamic mechanical analysis, a test specimen (2) is coupled to an excitation device (4) by means of a holder device (3). The excitation device (4) applies an excitation force comprised of a static pre-tensioning force component and a time-variable force component to the test specimen, and a deformation of the test specimen (2) is measured by means of one or more displacement sensors (5). The method includes a test phase with the steps: applying the excitation force to the test specimen; while said excitation force is in effect, determining at least one decision parameter, said decision parameter being indicative of a degree of slack in said coupling of the test specimen; comparing said decision parameter to at least one reference value; based on said comparison, determining whether or not the test specimen is coupled to the excitation device in a completely slack-free state, so that physical values derived from said measurements of the deformation will not be subject to errors caused by an insufficient amount of said pre-tensioning force component.