Affiliations: [a] School of Kinesiology and Health Science, York University, Toronto, ON, Canada | [b] Toronto Rehabilitation Institute, University Health Network, Toronto, ON, Canada
Correspondence:
[*]
Corresponding author: Janessa D.M. Drake, 2030 Sherman Health Science Research Centre, School of Kinesiology and Health Science, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada. Tel.: +1 416 736 2100, x. 33568; Fax: +1 416 736 5772; E-mail:jdrake@yorku.ca
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.
Keywords: Breast size, spine motion, spine posture, trunk muscle activation
