Abstract: The loading capacity of a core manufactured by reeling and gluing from paper or board layers, is tested by dynamically loading the core under conditions that simulate real life conditions. The core is mounted on a chuck, and the method is practiced by loading the core by utilizing a roll that exerts a nip pressure, and by rotating the core. One or both of the loading and the speed of rotation of the core are changed over time in a predetermined manner, to simulate the real life conditions. For example the loading on the core can be increased constantly while the rotational speed is kept constant, or the rotational speed is increased and the loading decreased corresponding to the real use situation caused by unwinding of a paper roll which is mounted by the core. The method also includes detecting any changes in the structure of the core, either optically, by sensing vibrational changes, or by sensing the break of an electrical wire passing through the core. Loading is continued until the core breaks.