Effects of obesity on breast size, thoracic spine structure and function, upper torso musculoskeletal pain and physical activity in women

Purpose: This study investigated the effects of obesity on breast size, thoracic spine structure and function, upper torso musculoskeletal pain and physical activity participation in women living independently in the community. Methods: A total of 378 women were divided into 3 groups (Not Overweight: body mass index (BMI) = 22.5 ± 0.2 kg/m² (mean ± SE); Overweight: BMI = 27.4 ± 0.3 kg/m²; Obese: BMI = 35.4 ± 0.3 kg/m²). Outcome variables of breast volume (mL), thoracic flexion torque (Nm), thoracic kyphosis (degrees), upper torso musculoskeletal pain (score) and time spent in physical activity (min) were calculated and compared among the 3 groups, adjusting for between-groups differences in age. Results: There was a significant main effect of BMI on all outcome variables. Participants classified as Obese displayed significantly larger breasts, had greater thoracic flexion torques and reported less time participating in physical activity relative to the participants who were classified as Not Overweight and Overweight. Participants in the Obese group also displayed significantly more thoracic kyphosis and reported significantly more upper torso musculoskeletal pain compared to their counterparts who were classified as Not Overweight. Conclusion: This study is the first to demonstrate that increased obesity levels were associated with compromised kyphosis and loading of the thoracic spine, as well as increased symptoms of upper torso musculoskeletal pain and reduced time spent in physical activity in women living in the community. We recommend further research to determine whether evidence-based interventions designed to reduce the flexion torque generated on the thoracic spine can improve these symptoms of upper torso musculoskeletal pain and the ability of women with obesity to participate in physical activity.