Ambulatory physiological measures obtained under naturalistic urban mobility conditions have acceptable reliability

Ambulatory assessment methods in psychology and clinical neuroscience are powerful research tools for collecting data outside of the laboratory. These methods encompass physiological, behavioral, and self-report measures obtained while individuals navigate in real-world environments, thereby increasing the ecological validity of experimental approaches. Despite the recent increase in applications of ambulatory physiology, data on the reliability of these measures is still limited. To address this issue, twenty-six healthy participants (N = 15 female, 18-34 years) completed an urban walking route (distance M = 2.2 km, ±SD = 0.11; duration M = 30.8 min, ±SD = 1.34; temperature M = 18.34° degree Celsius, ±SD = 1.19, Range = 16°-21° degrees Celsius) on two separate testing days, while assessing the effect of metabolic state (sated vs. fasted). GPS-location and ambulatory physiological measures (cardiovascular and electrodermal activity) were continuously recorded. The results showed no significant differences in single physiological measures between fasted and sated states. Bootstrapped test-retest reliabilities of single measures and aggregate scores derived via principal component analysis (PCA) were computed. The first principal component (PC#1) accounted for 39-45% of variance across measures. PC#1 scores demonstrated an acceptable test-retest reliability (r = .60) across testing days, exceeding the reliabilities of most individual measures (heart rate: r = .53, heart rate variability: r = .50, skin conductance level: r = .53, no. of skin conductance responses: r = .28, skin conductance response amplitude: r = .60). Results confirm that ambulatory physiological measures recorded during naturalistic navigation in urban environments exhibit acceptable test-retest reliability, in particular when compound scores across physiological measures are analyzed, a prerequisite for applications in (clinical) psychology and digital health.