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

## TL;DR

This study compares how people sit in lab settings versus real life, finding that unstable sitting in the lab best matches real-world spine posture.

## Contribution

The study introduces wearable motion sensors and Gaussian mixture models to compare lab and real-world lumbar spine postures.

## Key findings

- Unstable sitting in the lab correlated strongly with real-world spine posture and frequent sitting modes.
- Upright lab sitting correlated with the second most frequent real-world sitting mode.
- Less sitting and more walking in real life were linked to better balance and spine coordination.

## Abstract

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.