Exploring Lumbar Spine Posture and Movement in Sitting: A Comparison Between Laboratory and Real-World Measures

Background/Objectives: Sitting is linked to health problems, including back pain. Sitting posture is commonly measured in the laboratory, but it remains unclear how this relates to real-world spine posture. Methods: A cross-sectional study of pain-free adults conducted measurements in "laboratory" and "real-world" settings. Wearable motion sensors recorded lumbar spine angular orientation to compare lumbar spine flexion angle during sitting postures in between settings. Gaussian mixture models defined participant-specific modes and overall probability distributions of real-world sitting posture. Measures included periods of real-world sedentary/activity behaviours and trunk postural control (laboratory). Results: Laboratory measures of lumbar angle were more flexed during questionnaire (30.0°) than upright (19.8°) sitting. The angle in unstable sitting was intermediate (27.1°). Spine posture in unstable sitting correlated with real-world overall mean posture (r = 0.49-0.54) and most frequent mode (r = 0.47). Upright laboratory sitting posture correlated with real-world second most frequent mode (r = 0.54). Sitting less (r = 0.45) and walking more (r = 0.41) in the real world related to better balance performance and lumbar spine coordination. Conclusions: Spine posture in an unstable sitting laboratory task had the closest association with real-world sitting but does not replicate the diversity of spine postures adopted in real-world sitting. Wearable sensors are viable to study real-world postures.