Studies of three-dimensional trajectories of breast movement for better bra design

Zhou, Jie; Yu, Winnie; Ng, Sun Pui

doi:10.1177/0040517511435004

Cited by 31 publications

(33 citation statements)

References 18 publications

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“…However, even within the same type of investigation the number of trials used can vary widely between studies. For example, within the scientific literature on breast biomechanics during treadmill running the number of gait cycles analysed ranges from 5 (White et al 2011), through 15 (Zhou et al 2012) to 30 (McGhee et al 2013). Notably none of these studies provide strong justification for the number of trials used.…”

Section: Introductionmentioning

confidence: 99%

Selecting the number of trials in experimental biomechanics studies

Forrester

2015

International Biomechanics

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Experimental biomechanics studies often involve the comparison of mean values from individuals across two or more experimental conditions. The purpose of this study was to evaluate two existing methods for determining the number of trials necessary to estimate these means. The sequential estimation technique (SET) was investigated in terms of the influence of input data distribution on the outcome. Paired samples t-tests were investigated in terms of the interaction between the number of subjects and number of trials necessary to achieve an acceptable level of statistical power. Simulation models were developed to perform SET and paired samples t-tests on representative synthetic input data. The SET results confirmed that the number of trials to achieve a stable estimate of the mean is independent of the input distribution provided the mean and standard deviation are fixed. For the commonly used 20 reference trials and 0.25 standard deviation threshold 9 ± 8 trials were needed to achieve stability. The paired t-test results confirmed that both number of subjects and number of trials can have a marked effect on the statistical power, e.g. a power of 0.80 can be achieved for effect size of 0.80 using 15 subjects and at least 19 trials or 20+ subjects and only 3 trials. The SET method suffers from arbitrary convergence criteria and neglecting intra-subject variance and, thus, should be applied with extreme caution. In contrast, statistical power can provide a more objective and conclusive means for determining the number of trials required for a given experimental situation.

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Section: Introductionmentioning

confidence: 99%

Selecting the number of trials in experimental biomechanics studies

Forrester

2015

International Biomechanics

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“…During physical activities such as running, breast mass asymmetry may result in different kinematics for each breast based on the same driving force of the trunk. A single breast (left; Zhou, Yu, & Ng, 2012b;right;Bridgman, Scurr, White, Hedger, & Galbraith, 2010;White, Scurr, & Smith, 2009) is commonly used to make recommendations on improvements to breast support design (Zhou et al, 2012a) and to investigate the effect of breast support levels on breast kinematics and exercise-induced breast pain (Bridgman et al, 2010;Scurr et al, 2010;White et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Breast motion asymmetry during running

Mills

Risius

Scurr

2014

Journal of Sports Sciences

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Breast asymmetry is common in females, despite a similar driving force; dynamic activity may result in asymmetrical breast motion. This preliminary study investigated how breast categorisation (left/right or dominant/non-dominant) may affect breast support recommendations and its relationship with breast pain. Ten females ran on a treadmill at 10 kph in three breast supports (no bra, everyday bra, sports bra). Five reflective markers on the thorax and nipples were tracked using infrared cameras (200 Hz) during five running gait cycles in each breast support. Multiplanar displacements of both breasts were calculated relative to the thorax. Although the maximum individual participant difference was 2.4 cm (mediolaterally) between the left and right breast, no left/right differences were found in any direction or support condition. Notably, correlations between breast pain and anterioposterior breast displacement were stronger with the left breast (r = 0.614) and moderate with the right breast (r = 0.456). Following participant categorisation according to the greatest magnitude of superioinferior breast displacement (dominant breast), results showed significant differences in displacement for all directions across different breast supports. When using breast kinematic data to examine relationships with breast pain or to recommend breast support requirements, data on both breasts should be collected.

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“…The third trunk segment was developed via pilot work, which involved participants wearing a sample of six different bras ( Figure 3) in a random order, selected from published papers, 7,8,15 to determine possible marker locations, unobstructed by the majority of bra designs.…”

Section: Marker Placement and Trunk Segment Constructionmentioning

confidence: 99%

Trunk marker sets and the subsequent calculation of trunk and breast kinematics during treadmill running

Mills

Loveridge

Milligan

et al. 2015

Textile Research Journal

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Female participants present a unique challenge as the design of the bra used to support the breasts occludes the correct positioning of many recommended trunk marker sets. This study aimed to compare the effect of two existing and one new trunk marker set on the calculation of trunk and breast kinematics. Twelve females had markers placed on their trunk and right nipple; these markers were tracked using infrared cameras during five running gait cycles and used to define three trunk calculation methods. Trunk 1: suprasternal notch, right and left ribs; Trunk 2: supersternal notch, processus xiphoideus, 7th cervical and 8th thoracic spinous process; Trunk 3: Trunk 2 plus a marker 33% from the suprasternal notch to the processus xiphoideus, and another 50% between the 7th cervical and 8th thoracic spinous process. Trunk segment capture success, segment origin instability, segmental residual, trunk kinematics and breast range of motion (relative to the trunk segment), were calculated for each trunk segment. Segment capture success varied from 88% (Trunk 1) to 100% (Trunk 2 and 3). Segment origin instability ranged from 0.2 cm (Trunk 2 and 3) to 1.5 cm (Trunk 1). Maximum trunk extension differed by 7° and breast range of motion varied by 41% (anterioposterior), 54% (mediolateral), and 21% (superioinferior) between trunk calculation methods. The selection of marker set used to construct the trunk segment is critical before recommending improvements to bra design to improve breast support. The Trunk 3 marker set is recommended for subsequent breast research.

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Studies of three-dimensional trajectories of breast movement for better bra design

Cited by 31 publications

References 18 publications

Selecting the number of trials in experimental biomechanics studies

Selecting the number of trials in experimental biomechanics studies

Breast motion asymmetry during running

Trunk marker sets and the subsequent calculation of trunk and breast kinematics during treadmill running

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