This paper evaluates self-tracking practices in connection with ideas of objectivity via exploration of confrontations with personal data, particularly with reference to physiological stress and recovery measurements. The discussion departs from the notion of 'mechanical objectivity', seeking to obtain evidence that is 'uncontaminated by interpretation'. The framework of mechanical objectivity tends, however, to fall short when people translate physiological measurements to fit their expectations and everyday experiences. We develop the concept of 'situated objectivity' with the goal of highlighting the everyday as a domain of interpretation, reflection and ambiguity, proposing that the concept offers an analytical entry point to a more profound understanding of how people engage with their personal data. Everyday data encounters are not methodical and systematic, but combine knowledge in an eclectic manner. Framed in this way, self-tracking practices are less occupied with 'facts of life' than translating and transforming life based on earlier experiences, cultural understandings and shared expectations. Paradoxically, new measurement devices and software, which are supposed to be based on sound, universal and generalisable principles, hard facts and accurate descriptions, become raw material for daily decisions, as people seek bespoke answers and craft personalised theories of health and life. From this perspective, self-tracking measurements can be used to experiment and learn, gaining value in relation to the communicative processes that they promote and contributing to possibilities for rethinking health knowledge and health promotion.
Keywords: Mechanical objectivity; data valences; self-tracking; situated objectivity; stress; temporality.