There are two sides to every story: implications of asymmetry on breast support requirements for sports bra manufacturers.

This study aimed to investigate: (1) the prevalence and magnitude of breast movement asymmetry, (2) the interaction between static and dynamic breast asymmetry and (3) the influence of sports bras on breast asymmetry during running. Position data were collected from 167 females whilst treadmill running and then a sub-group of 12 participants in different bra conditions. Breast movement asymmetry existed in 89% of participants, with resultant static breast position asymmetry larger in participants displaying dynamic asymmetry. Asymmetry was most commonly caused (60% to 75%) by greater movement of the left breast. No significant relationships were found between asymmetry and bra size or breast pain. Sports bras reduced asymmetry prevalence from 75% to 33% of participants in the antero-posterior direction but only from 75% to 67% of participants in the infero-superior direction. The magnitude of range-of-motion asymmetry reduced from 67 mm with no bra to between 6 and 64 mm in-bra in the infero-superior direction, with the best performing bra incorporating encapsulating cups and adjustable straps and underband. It is recommended that sports bras allow underband and strap adjustment to facilitate individual breast support and that asymmetry is considered when designing and fitting bras, which could utilise resultant asymmetry measured statically.

Understanding key performance indicators for breast support: An analysis of breast support effects on biomechanical, physiological and subjective measures during running.

To assess the effectiveness of breast support previous studies monitored breast kinematics and kinetics, subjective feedback, muscle activity (EMG), ground reaction forces (GRFs) and physiological measures in isolation. Comparing these variables within one study will establish the key performance variables that distinguish between breast supports during activities such as running. This study investigates the effects of changes in breast support on biomechanical, physiological and subjective measures during running. Ten females (34D) ran for 10 min in high and low breast supports, and for 2 min bare breasted (2.8 m·s-1). Breast and body kinematics, EMG, expired air and heart rate were recorded. GRFs were recorded during 10 m overground runs (2.8 m·s-1) and subjective feedback obtained after each condition. Of the 62 variables measured, 22 kinematic and subjective variables were influenced by changes in breast support. Willingness to exercise, time lag and superio-inferior breast velocity were most affected. GRFs, EMG and physiological variables were unaffected by breast support changes during running. Breast displacement reduction, although previously advocated, was not the most sensitive variable to breast support changes during running. Instead breast support products should be assessed using a battery of performance indicators, including the key kinematic and subjective variables identified here.

The influence of breast support on torso, pelvis and arm kinematics during a five kilometer treadmill run.

Many women wear sports bras due to positive benefits associated with these garments (i.e. reduction in breast movement and breast pain), however the effects these garments have on upper body running kinematics has not been investigated. Ten female participants (32 DD or 34 D) completed two five kilometer treadmill runs (9 km h(-1)), once in a low and once in a high breast support. The range of motion (ROM) and peak torso, pelvis, and upper arm Cardan joint angles were calculated over five gait cycles during a five kilometer run. Peak torso yaw, peak rotation of the pelvis, peak pelvis obliquity, ROM in rotation of the pelvis, and ROM in upper arm extension were significant, but marginally reduced when participants ran in the high breast support. The running kinematics reported in the high breast support condition more closely align with economical running kinematics previously defined in the literature, therefore, running in a high breast support may be more beneficial to female runners, with a high breast support advocated for middle distance runners.

Magnitude of multiplanar breast kinematics differs depending upon run distance.

Recommendations for breast support, dynamic breast pain assessment, and implications for sports performance have been made within breast biomechanics research; however, these studies have been based upon short exercise protocols (2-5 min). The aim of this study was to investigate the effect of breast support on multiplanar breast kinematics over a 5-kilometre run. Ten female participants (34D or 32DD) conducted two 5-kilometre runs, in a low and high breast support. Relative multiplanar breast kinematics were averaged over five gait cycles at six intervals of a 5-kilometre run. Increases in multiplanar breast kinematics were reported from the start to the end of the run, with the greatest rate of increase in breast kinematics reported within the first two kilometres of running. The greatest relative increases in breast range of motion (34%), velocity (33%), and acceleration (41%) were reported in the superioinferior direction at the fifth kilometre (33 min of running) in the high breast support. Key findings suggest that the run distance, and therefore run duration, employed for both fundamental research and product validation protocols should be carefully considered and it is suggested that running protocols for assessing breast biomechanics should exceed 7 min.

Multiplanar breast kinematics during different exercise modalities.

Multiplanar breast movement reduction is crucial to increasing physical activity participation amongst women. To date, research has focused on breast movement during running, but until breast movement is understood during different exercise modalities, the breast support requirements for specific activities are unknown. To understand breast support requirements during different exercise modalities, this study aimed to determine multiplanar breast kinematics during running, jumping and agility tasks. Sixteen 32D participants had markers attached to their right nipple and torso. Relative multiplanar breast displacement was calculated during bare-breasted treadmill running (10 kph), maximum countermovement jumping and an agility t-test. Exercise modality influenced the magnitude and direction of breast displacement, velocity and acceleration (p < .05). Jumping produced greater vertical breast displacement (.09 m) but less mediolateral breast displacement (.05 m) than running or the agility task, but agility tasks produced the highest multiplanar breast velocities and acceleration. Breast movement during jumping was predominantly in the vertical direction, whereas the agility task produced a greater percentage of mediolateral breast acceleration than running or jumping. Exercise modality impacted upon the magnitude and distribution of bare-breasted multiplanar breast kinematics in this homogenous 32D cohort. Therefore, to reduce breast movement in women of a 32D bra size, manufacturers may wish to design sport-specific products, with greater vertical support for exercise modalities incorporating jumping and greater mediolateral support for agility tasks.

The effect of breast support on upper body muscle activity during 5 km treadmill running.

Breast support has previously been shown to influence surface EMG of the pectoralis major during running. Reductions in muscle activity have previously been associated with a reduction in energy cost, which may be advantageous for female runners. Ten female participants performed two self-paced (average pace 9 km h(-1)) 5 km treadmill runs under two breast support conditions (low and high); an additional bare-breasted 2 min run was also conducted. Surface EMG electrodes were positioned on the pectoralis major, anterior deltoid, medial deltoid, and upper trapezius, with data collected during the first 2 min of running and each kilometer interval thereafter. Reductions in peak EMG of the pectoralis major, anterior and medial deltoid were reported when participants ran in the high breast support during the initial intervals of the run (up to the second kilometer). The increased activation in the pectoralis major, anterior and medial deltoid in the low breast support may be due to increased tension within these muscles, induced by the greater breast pain experienced in the low breast support. This may be a strategy to reduce the independent breast movement causing the pain through increased muscular activation. This study further promotes the use of a high breast support during running with potential benefits for treadmill running associated with reductions in muscular demand during a 5 km run.

Is torso soft tissue motion really an artefact within breast biomechanics research?

For rigid body POSE estimation, any relative movement of the tracking markers on a segment is often referred to as an artefact; however this may be an important part of the signal within breast biomechanics. This study aimed to quantify differences in breast range of motion when calculated relative to the torso segment using either direct or segment optimised POSE estimation algorithms. Markers on the torso and right nipple were tracked using infrared cameras (200 Hz) during five running gait cycles in three breast support conditions (no bra, everyday bra and sports bra). Multiplanar breast range of motion was calculated relative to the torso segment using two POSE estimation algorithms. First, the torso segment was defined using direct POSE estimation (direct). Second, while standing stationary in the anatomical position; the positional data of the torso markers were used to construct the torso using segment optimised POSE estimation (optimised). The torso segment length defined using direct POSE estimation changed significantly by 3.4 cm compared to that of the segment optimisation POSE estimation in the no bra condition. Subsequently, superioinferior breast range of motion was significantly greater (p<0.017) when calculated using direct POSE estimation, within each of the three breast support conditions. Segment optimisation POSE estimation is recommended to minimise any differences in breast motion associated with intra segment deformation between physical activity types. However, either algorithm is recommended when evaluating different breast support garments, as a correctly fitted bra does not cause the torso markers to move relative to each other.

Can axes conventions of the trunk reference frame influence breast displacement calculation during running?

To obtain breast motion relative to the trunk, skin markers are used to define a local coordinate system (trunk), with respect to the global reference frame. This study aimed to quantify any differences in multiplanar breast displacement relative to the trunk using the first axis of rotation as either the mediolateral or longitudinal axis. Ten female participants ran on a treadmill (10 kph) in three different breast supports (no bra, everyday bra, sports bra). Four reflective markers placed on the trunk and right nipple were tracked using eight infrared cameras (200 Hz) during five running gait cycles in each breast support condition. Following marker identification, right breast multiplanar displacements were calculated relative to the trunk using either the mediolateral axis or the longitudinal axis as the first rotational axis to define the orthogonal local coordinate system. Results showed that there was a significant difference (8.2%) in superioinferior breast displacement in the sports bra condition when calculated using different axes conventions for the trunk segment. Furthermore, the greatest magnitude of breast displacement occurred in a different direction depending upon the selection of the first rotational axis. The definition of the primary reference axis of the trunk significantly alters the magnitude of superioinferior breast displacement and therefore it is recommended that the previously reported 'stable' longitudinal axis should be defined as the first rotational axis during running. Caution should also be used as the axes convention influences the magnitude and direction of breast support requirements, which has important implications for bra design.

Within-participant variance in multiplanar breast kinematics during 5 km treadmill running.

More and more studies are emerging reporting breast kinematics. These studies rarely present effect sizes, power, and variance in the data. Important inferences are drawn from these data, including applications to product design, breast pain assessment, sports performance effects, and more. The aim of the study was to explore the within-participant variance in breast kinematic data during a 5 km run. Multiplanar breast kinematics and within-participant variance, defined by the coefficient of variation, for 10 female participants wearing a low and high level breast support were calculated during a 5 km run. Greater within-participant variance was reported in the high level (mean=15%) breast support compared with the low level (mean=12%). Within-participant variance in breast kinematics did not change over the 5 km run. Differences in the magnitude of within-participant variance in breast kinematics were reported between directions of breast movement, with greater levels in the anteroposterior direction compared with mediolateral and vertical. It is important for the progression of this research area that the presence and sources of within-participant variance in breast kinematics are quantified and acknowledged, ensuring that the margin for meaningful differences can be reported.

Predictors of three-dimensional breast kinematics during bare-breasted running.

PURPOSE: This study aimed to analyze differences in breast kinematics between breast cup sizes during running and the ability of breast and body size measurements to explain these differences. METHODS: Forty-eight women (A to G cup; mean ± SD: age = 26.0 ± 6.0 yr, stature = 1.667 ± 0.064 m, mass = 62.78 ± 8.24 kg) with chest sizes of 32 to 38 inches participated. Chest and breast girths, a restricted anthropometric profile, suprasternal notch to nipple distances, and body mass index were measured, and breast mass was estimated. Multiplanar relative breast displacement, velocity, and acceleration during treadmill running were then recorded. Differences in breast kinematics were compared between cup sizes before and after allometric/polynomial scaling using significant breast and body size measures. RESULTS: All kinematic variables significantly increased with breast cup size (P < 0.05). Mean anterior-posterior (a/p), medial-lateral (m/l), and vertical bare-breasted displacements ranged from 0.030 to 0.059 m, from 0.018 to 0.062 m, and from 0.042 to 0.099 m, respectively, across A to G cups. Breast velocities ranged from 0.428 to 1.244 m·s(-1) (a/p), 0.411 to 1.708 m·s(-1)(m/l), and 0.819 to 2.174 m·s(-1) (vertical), respectively. Increases in breast acceleration varied from 11.664 to 48.438 m·s(-1) (a/p), 15.572 to 51.987 m·s(-1) (m/l), and 23.301 to 66.447 m·s(-1) (vertical), respectively. Scaling models found that breast mass was the only anthropometric measure to consistently explain differences in breast kinematics between cup sizes. CONCLUSIONS: Bare-breasted kinematics significantly increased with cup size during running. Differences in breast displacement, velocity, and acceleration between cup sizes could be predicted using estimates of breast mass based on conventional brassiere sizing. These data inform the design and evaluation of effective bra support.

The relationship between breast size and anthropometric characteristics.

OBJECTIVES: Current clinical selection criteria for mammaplasty use weight-related parameters, and weight loss is recommended as a nonsurgical intervention to reduce breast size. However, research has not firmly established if breast size is related to body size and composition. This study aims to investigate anthropometric characteristics in smaller and larger breasted women and identify predictors of breast mass. METHODS: A bra fitter determined underband and cup size of 93 A to H cup size women (mean ± standard deviation, age 25.7 ± 5.6 years, height 1.67 ± 0.6 cm, and mass 65.6 ± 11.0 kg). Estimations of breast mass (g) were made, and participants were categorized as smaller (<500 g) or larger (>500 g) breasted. Restricted anthropometric profiles determined body mass, height, body mass index (BMI), waist-to-hip ratio, sum of eight skinfolds, subscapular to triceps skinfold ratio, somatotype, percent body fat, fat and fat-free mass, and suprasternal notch to nipple distance. RESULTS: All variables (excluding height, subscapular to triceps skinfold ratio, and age) were significantly greater in larger breasted women. Body mass-related parameters and suprasternal notch to nipple distance were positively related to breast mass, with BMI and suprasternal notch to nipple distance accounting for half of the variance in breast mass. CONCLUSION: Smaller and larger breasted women demonstrate differences in anthropometry, with body mass and BMI demonstrating strong relationships to breast mass. Measures of BMI and suprasternal notch to nipple distance enable predictions of breast mass and suggest that weight-related parameters are not appropriate exclusion criteria for mammaplasty.