What is the effect of prolonged sitting and physical activity on thoracic spine mobility? An observational study of young adults in a UK university setting.

OBJECTIVE: Sedentary behaviour has long been associated with neck and low back pain, although relatively little is known about the thoracic spine. Contributing around 33% of functional neck movement, understanding the effect of sedentary behaviour and physical activity on thoracic spinal mobility may guide clinical practice and inform research of novel interventions.

DESIGN: An assessor-blinded prospective observational study designed and reported in accordance with Strengthening the Reporting of Observational Studies in Epidemiology.

SETTING: UK university (June-September 2016).

PARTICIPANTS: A convenience sample (18-30 years) was recruited and based on self-report behaviours, the participants were assigned to one of three groups: group 1, sitters-sitting >7 hours/day+physical activity<150 min/week; group 2, physically active-moderate exercise >150 min/week+sitting <4 hours/day and group 3, low activity-sitting 2-7 hours/day+physical activity <150 min/week.

OUTCOME MEASURES: Thoracic spine mobility was assessed in the heel-sit position using Acumar digital goniometer; a validated measure. Descriptive and inferential analyses included analysis of variance and analysis of covariance for between group differences and Spearman's rank correlation for post hoc analysis of associations.

RESULTS: The sample (n=92) comprised: sitters n=30, physically active n=32 and low activity n=30. Groups were comparable with respect to age and body mass index.Thoracic spine mobility (mean (SD)) was: group 1 sitters 64.75 (1.20), group 2 physically active 74.96 (1.18) and group 3 low activity 68.44 (1.22). Significant differences were detected between (1) sitters and low activity, (2) sitters and physically active (p<0.001). There was an overall effect size of 0.31. Correlations between thoracic rotation and exercise duration (r=0.67, p<0.001), sitting duration (r=-0.29, p<0.001) and days exercised (r=0.45, p<0.001) were observed.

CONCLUSIONS: Findings evidence reduced thoracic mobility in individuals who spend >7 hours/day sitting and <150 min/week of physical activity. Further research is required to explore possible causal relationships between activity behaviours and spinal musculoskeletal health.