Author(s): RENWICK, N., WHITE, J., JONES, B., WAKEFIELD-SCURR, J., Institution: UNIVERSITY OF PORTSMOUTH, Country: UNITED KINGDOM, Abstract-ID: 1139

INTRODUCTION:
Breast biomechanics research is largely focused on reporting discrete measures of nipple displacement during various activities. Evaluating breast movement continuously across the gait cycle may provide insight into when and for how long across the gait cycle sports bras are effective at reducing breast kinematics which may more closely correlate with changes in perceived breast support and pain. This study aims to compare discrete and continuous breast kinematic variables and to assess their relationship with perceived breast support and pain.
METHODS:
Thirty-six females (mode bra size 34D) ran on a treadmill bare-breasted and in a sports bra. Electromagnetic sensors captured nipple motion and calculated it relative to a torso reference system (1); gait cycles were identified from right foot contact. Participants rated perceived breast support and pain (scale 0 to 10). Nipple displacement was reported as range of motion (ROM), peak values and breast movement reduction (2); nipple velocity and acceleration were calculated as first and second derivatives of nipple position and reported as peak values; these discrete values were calculated over ten gait cycles and averaged. Data were checked for normality using Shapiro-Wilk tests; Wilcoxon signed-rank or paired samples t-test compared between breast support conditions. Time histories for relative nipple position (normalised and non-normalised), velocity and acceleration were averaged across ten gait cycles for each participant and compared between breast support conditions using one-dimensional statistical parametric mapping (SPM) (3). Spearman’s rho correlation coefficients assessed the relationship between breast support and pain with kinematic variables.
RESULTS:
Nipple displacement, velocity and acceleration were significantly reduced in sports bra running compared to bare-breasted running for all discrete variables except peak lateral displacement (p=0.156). SPM identified multiple points across the gait cycle where the sports bra reduced breast movement; superior-inferior normalised displacement was reduced for the largest duration of the gait cycle (87%). Median score for breast support in the bra condition was 8. Median scores for perceived breast pain were 5 and 0 for bare-breasted and bra running, respectively. The strongest relationship with perceived support was reported for superior-inferior ROM (r=0.857; p=<0.001); strongest relationship with breast pain was reported for anterior-posterior peak negative acceleration (r=0.715; p=<0.001).
CONCLUSION:
Discrete measures of breast kinematics have a stronger relationship to perceived breast pain and support compared to continuous measures but continuous measures can identify when during the gait cycle a sports bra is most effective at reducing breast movement.
REFERENCES:
1) Mills et al., J, Biomech, 2016
2) Norris et al., Ergonomics, 2021
3) Pataky, J, Biomech, 2010