Current approaches to the postural assessment of horse riders is highly subjective, with a lack of consistency between practitioners. A technology-based solution would remove the human perspective and enable a more consistent, accurate and objective assessment to be carried out. This paper provides preliminary insights on the use of a customised method based on contextual inquiry for gathering contextual data in an unusual, in the wild context. This will be used to determine a standardised data collection protocol and context-specific interface design for an inertial motion sensor based rider assessment tool.