A portable apparatus comprising: means for storing user profiles of a group, each user profile specifying user-specific parameters; and means for performing a selection of a user profile automatically, without a user interacting with a user interface of the portable apparatus, or semi-automatically, the user accepting a user profile suggested in the user interface of the portable apparatus, from among the user profiles of the group stored in the means for storing on the basis of a predetermined condition; characterized in that each user profile includes a time of exercise and the portable apparatus further comprises: means for modifying an exercise data processing configuration of the portable apparatus on the basis of the selected user profile; wherein the means for modifying is further configured to modify as the exercise data processing configuration of the portable apparatus at least one of an activity calculation algorithm, an energy expenditure calculation algorithm, a motion detection based activity threshold, a fitness test algorithm, heart rate zone limits, mode of exercise data display; and the portable apparatus further comprises a clock configured to provide a clock time to the means 306) for modifying, and the means for modifying is further configured to perform the selection utilizing the clock time as a part of the predetermined condition, thereby enabling the automatic or semi-automatic selection of the user profile from among the user profiles of the group stored in the means for storing whose time of exercise matches the clock time. means for storing user profiles of a group, each user profile specifying user-specific parameters; and means for performing a selection of a user profile automatically, without a user interacting with a user interface of the portable apparatus, or semi-automatically, the user accepting a user profile suggested in the user interface of the portable apparatus, from among the user profiles of the group stored in the means for storing on the basis of a predetermined condition; characterized in that each user profile includes a time of exercise and the portable apparatus further comprises: means for modifying an exercise data processing configuration of the portable apparatus on the basis of the selected user profile; wherein the means for modifying is further configured to modify as the exercise data processing configuration of the portable apparatus at least one of an activity calculation algorithm, an energy expenditure calculation algorithm, a motion detection based activity threshold, a fitness test algorithm, heart rate zone limits, mode of exercise data display; and the portable apparatus further comprises a clock configured to provide a clock time to the means 306) for modifying, and the means for modifying is further configured to perform the selection utilizing the clock time as a part of the predetermined condition, thereby enabling the automatic or semi-automatic selection of the user profile from among the user profiles of the group stored in the means for storing whose time of exercise matches the clock time. means for modifying an exercise data processing configuration of the portable apparatus on the basis of the selected user profile; wherein the means for modifying is further configured to modify as the exercise data processing configuration of the portable apparatus at least one of an activity calculation algorithm, an energy expenditure calculation algorithm, a motion detection based activity threshold, a fitness test algorithm, heart rate zone limits, mode of exercise data display; and the portable apparatus further comprises a clock configured to provide a clock time to the means 306) for modifying, and the means for modifying is further configured to perform the selection utilizing the clock time as a part of the predetermined condition, thereby enabling the automatic or semi-automatic selection of the user profile from among the user profiles of the group stored in the means for storing whose time of exercise matches the clock time.