title: Breast size impacts spine motion and postural muscle activation.
abstract: BACKGROUND
  While it is generally accepted that large breast sizes in females contribute to back pain and poor posture, the effects of breast size on spinal motion and muscle activation characteristics are poorly understood.
  
  
  OBJECTIVE
  This study examined the relationship between breast size, spine motion, and trunk muscle activation.
  
  
  METHODS
  Fifteen university-aged females, free of back pain symptoms, were tested. Breast sizes were calculated, and three-dimensional spine motion and activation from five trunk muscles bilaterally were measured during standing and trunk flexion movements. Correlations between breast size and motion and muscle activation measures were assessed.
  
  
  RESULTS
  Head and trunk angles were strongly, negatively correlated to breast size during upright standing; thoracic angles were moderately, positively correlated to breast size during thoracic flexion movements. Trunk muscles showed positive, moderate-strength relationships with breast size during upright standing and some trunk movements.
  
  
  CONCLUSIONS
  These findings provide a preliminary indication that increasing breast sizes are associated with altered postures and increased muscle activation in a non-clinical population, and constitute a baseline for the study of females with a full range of breast sizes. Further research is required to confirm the generalizability of these findings to other sizes, in order to inform strategies for the prevention or reduction of back pain, as well as diagnosis, treatment, and rehabilitation techniques associated with breast size and back pain.
authors.affiliation: School of Kinesiology and Health Science, York University, Toronto, ON, Canada.|Toronto Rehabilitation Institute, University Health Network, Toronto, ON, Canada.
authors.forename: Alison
authors.initials: A
authors.lastname: Schinkel-Ivy
authors.affiliation: School of Kinesiology and Health Science, York University, Toronto, ON, Canada.
authors.forename: Janessa D M
authors.initials: JD
authors.lastname: Drake
mesh_terms: D001940:Breast / Q000033:anatomy & histology*; D004576:Electromyography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009929:Organ Size; D011187:Posture / Q000502:physiology*; D013131:Spine / Q000502:physiology*; D060726:Torso / Q000502:physiology; D055815:Young Adult
keywords: Breast size; spine motion; spine posture; trunk muscle activation