Prolonged sitting and physical inactivity are associated with limited hip extension: A cross-sectional study

Background: It is possible that physical inactivity and prolonged sitting could lead to changes in muscle properties or bony limitations which may reduce passive hip extension. Objectives: This study explored the association between passive hip extension and sitting/physical activity patterns. Design: Cross sectional study. Method: The modified Thomas Test is a clinical test used to characterise hip flexion contracture. This test was used to measure passive hip extension across 144 individuals. In addition, sitting behaviours and physical activity patterns were quantified using the Global Physical Activity Questionnaire. Cut off points were defined for low/high physical activity (150 min per week), prolonged sitting (>7 h per day) and minimal sitting (<4 h per day). ANOVA testing was then used to compare passive hip extension between three groups, defined using the specified thresholds: low activity & prolonged sitting, high activity & minimal sitting and high activity & prolonged sitting. Results: A total of 98 participants were allocated to one of the three groups which were shown to differ significantly in passive hip extension (P < 0.001). Importantly, there was 6.1 degrees more passive hip extension in the high activity & minimal sitting group when compared to the low activity & prolonged sitting group. Conclusion: This study is the first to demonstrate an association between passive hip extension and prolonged sitting/physical inactivity. It is possible that these findings indicate a physiological adaptation in passive muscle stiffness. Further research is required to understand whether such adaptation may play a role in the aetiology of musculoskeletal pain linked to prolonged sitting.