Biosensing measures of physiological (somatic) response offer a potentially powerful tool for capturing people's subconscious reactions to environmental stimuli. Combining biosensing with other techniques allows insights to be generated not only about the intensity of somatic response but also, crucially, the underlying causes of that response. Despite pioneering work in this area, a rigorous, empirically-led analysis of biosensing measures in mixed methods research has hitherto been lacking. We address this lacuna through a case study of urban walking, comparing a field-based study (30 participants) with a virtual exercise undertaken in a lab (25 participants). Combining biosensing with data on environmental stimuli (recorded using video/GPS) and interviews, three analytical modes are examined: biosensing-led; environment-led; and thematic-led. The analysis shows how each dataset can add contextualizing information to significant phenomena observed in the others. We demonstrate, however, that biosensing measures become considerably more difficult to interpret beyond the controlled environment of the lab. The paper concludes that biosensing should be seen as a valuable measure in field studies, but one which requires careful interpretation through other datasets, being of limited usefulness and reliability taken alone.