Project Final Report

Test of effectiveness of the Shefit sport brassiere

26 April 2018

Submitted by:

Joseph E. Langenderfer

Ksenia I. Ustinova

1

Abstract

The purpose of this study was to measure the performance of the sport brassiere at

reducing undesirable and uncomfortable breast motion when subjects engaged in 5

common exercises. The resulting breast displacement (hereafter referred to as “breast

motion”) and accelerations (hereafter referred to as “breast bouncing”) were compared to

that encountered when the same subjects wore four similar competitive sports bras. For

nearly all performance outcomes, the sport bra resulted in the largest reductions in breast

motion and bouncing compared to other bras. Additionally, when observing differences

across exercises and outcomes, the sport brassiere reduced the undesirable motion in a

more consistent manner when compared to other bras. For vertical motion, across all

exercises, the sport brassiere resulted in the greatest average reduction (25-38%

depending on exercise) compared to the other bras. Across all exercises, on average the

sport brassiere provided 28% greater reduction in vertical bouncing compared to all other

bras. For lateral (side-to-side) outcomes, the sport brassiere was somewhat less consistent

in performance and did not always reduce motion and bouncing more than the other bras,

although on average the sport brassiere still performed well. When subjects evaluated bra

performance in terms of comfort and ease of use, the sport brassiere was rated better than

the other bras in terms of performance and ease of use, but there were no differences in

how the bras felt, or in terms of pain and discomfort.

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Introduction

Motion of the breasts and their subsequent support from brassieres has been

examined extensively in previous studies involving both experimental measurements

(Wood, White et al. , Bridgman, Scurr et al. 2010, Milligan, Mills et al. 2015) and computer

models (Cai, Chen et al. 2018). However, very few of these studies (Lorentzen and Lawson

1987, White, Scurr et al. 2009) have compared the effectiveness of different brassieres at

supporting the breasts and reducing undesirable kinematics resulting from vigorous

exercise or activity.

The purpose of this study was to measure kinematics of breast motion when

subjects wore 5 different brassieres, as well as the natural (Control) condition, and to

compare the kinematics of breasts for different brasseries and for the Control condition.

The hypothesis was that the sport brassiere would be most effective at reducing breast

motion and bouncing when compared to other brassieres.

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Methods

An experimental paradigm was developed to allow for the recording of motion capture

data of subjects wearing the five different brassieres and wearing no bra (Control)

condition while engaging in five different exercises.

Subjects and Experimentation

The experimentation was performed in a state of the art motion capture facility with

instrumentation suitable for standard measurements common in whole body biomechanics

and motor control experimental paradigms. The Motion Analysis Center is a modern

facility dedicated to the study of human movement. Housed in the Physical Therapy

program, the center emerged from a partnership between the Colleges of Health

Professions and Engineering and Technology. The center's mission is to create an

environment which promotes collaboration among a diverse group of researchers and

integration of theoretical knowledge with clinical experience. Latest in motion capture

technology, virtual reality equipment, and custom devices developed at CMU. Research in

virtual rehabilitation, human development, biomechanical modelling, motor control, and

development of quantification tools for the clinic. Generously supported by the National

Science Foundation.

Thirty subjects were recruited to participate in the study. After explanation of the

study and familiarization with the instrumentation, subjects were informed of associated

risks and provided written informed consent to participate in testing in accordance with

requirements of the Institutional Review Board at Central Michigan University. Subjects

were recruited from women active in sports and exercise programs in the local and university

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communities. Consequently, these subjects’ breasts were of a wide array of size

measurements from a traditional AA through traditional DD+ (Table 1). After pre-

measurement for breast size and fitting by a trained bra fitter in order to ensure that

properly sized brassieres were worn during the experiments, each subject received one

correctly fitted bra of each type as compensation for participation.

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Table 1: Subject measurements

Chest band (inch) Bust band (inch) Cup Size (inch)

28.3 33.3 4.9

32.5 36.8 4.3

31.1 36.8 5.7

30.7 34.4 3.7

32.1 37.8 5.7

36.0 43.7 7.7

30.5 34.4 3.9

29.5 33.5 3.9

30.1 33.9 3.7

29.9 35.4 5.5

31.1 36.4 5.3

32.1 37.3 5.2

32.3 37.6 5.3

27.0 31.3 4.3

29.7 35.4 5.7

28.3 31.7 3.3

29.7 35.2 5.5

27.0 31.1 4.1

37.6 41.1 3.5

35.0 42.5 7.5

32.5 38.6 6.1

33.1 38.0 4.9

34.6 39.4 4.7

37.0 45.5 8.5

40.9 46.9 5.9

39.6 46.7 7.1

35.4 40.2 4.7

Following familiarization of the testing session and nature of the five exercises: high

knees, jumping jacks, running from a standing start to distance of 12 meters, side twists,

and walking a distance of 12 meters, subjects were instrumented with retro-reflective

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markers. The high knees and jumping jacks trials were for 7 seconds duration during which

subjects accomplished 5 repetitions of the exercise. For each subject, the five exercises

were performed in the same order, and the order of brassieres (and Control condition) was

randomized. Subjects performed 3 trials of each exercise. Of the 47 markers applied to the

subjects, 39 markers were placed on anatomical landmarks according to the Plug-in-Gait

Full Body Model and 4 markers were applied to each breast, or on the brassiere over the

breast (Figure 1). Marker motions were recorded with a 12-camera Vicon T160 Motion

Capture system at 100 Hz. Instructions to each subject were to perform each exercise in a

relatively quick but comfortable and controlled motion. As such, subjects practiced each

exercise until comfortable with the motion.

After testing each brassiere, subjects rated each brassiere on a 0-10 numerical

visual analog scale where: 0 represents comfortable (no pain), 5 represents uncomfortable,

and 10 corresponds to painful. At the end of testing for all brassieres subjects were asked

to answer two open-ended questions: “Which brassiere felt and performed the best?” and,

“Which brassiere was easier to don and doff?”

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Figure 1: Subject performing exercise with 47 markers attached. 39 markers applied to anatomical landmarks in accordance with the standard plug-in-gait model and 8 markers were applied to both breasts.

Data and Analysis

Following recording of marker data with Vicon, data files were backed up to a

network data server. Files contain no subject specific personal information and only refer

to subject and trials by an alphanumeric code. The data files were then processed by an

experienced and trained analyst to ensure correct marker identification and then exported

to a standard data file format, which lists the Cartesian coordinates [X, Y, Z] of each marker

attached to a subject over the time duration of the motion trial. These coordinate files were

then processed through custom written scripts (Matlab, Mathworks, Natick, MA) prepared

specifically for this project in order to make the computations required to calculate

kinematics describing the motion of each subject. For consistent comparison of breast

motion across subjects of varying anthropometry a standard procedure was developed.

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The first step in performing these calculations was to use coordinates of markers attached

to tenth thoracic and seventh cervical vertebra, as well as left and right shoulders, to

virtually construct a coordinate system located on the thorax. This thorax coordinate

system was used to calculate the three-dimensional displacement of the right breast nipple

marker relative to the always-moving subject thorax and to measure subject performance

velocity for each exercise. Subject performance velocity was calculated as thorax vertical

velocity for high knees and jacks, as horizontal velocity for the side twists and as forward

velocity for walking and running. A 10 Hz Butterworth filter was applied to the breast

displacement data and successively to breast acceleration (Wood, White et al.). Breast

acceleration was determined with two successive calculations of numerical forward-

differentiation. In order to aid interpretation, the three-dimensional displacements and

accelerations were then referred to the thorax based coordinate system in order to

calculate displacement and acceleraton in meaningful anatomical directions: superior-

inferior (up-down) and medial-lateral (side-side). As is common in gait analysis studies,

data from the initial and final time portions of each trial were cropped (i.e. excluded) from

calculations in order to eliminate subject start effects and slowing as trials were nearly

completed. Maximum displacements (motion) and accelerations (bouncing) of the right

breast were extracted from the trials in order to make comparison between brassieres for

each exercise condition. From these maximum values, means and standard errors were

calculated in order to summarize the data. Maximum values for displacement and

acceleration outcomes were then analyzed with ANOVA to determine if differences in mean

maximum outcomes were significant between brassieres. Following initial ANOVA for each

outcome, secondary ANOVAs were performed to assess if differences existed between

9

brassieres within a given exercise. When ANOVA revealed significant differences, pair-wise

post-hoc comparisons were performed between individual brassieres with Tukey-Kramer

Honest Significant Difference criterion.

Analysis and interpretation was performed by a principal investigator and co-

principal investigator each with more than 15 years’ experience in biomechanics and

motor control research, and each with more than 25 peer-reviewed publications in these

disciplines.

Ksenia Ustinova, Ph.D. is a professor in the School of Rehabilitation and Medical

Sciences, Doctoral Program in Physical Therapy. Degrees include B.S. Physical

Education/Physical Therapy - State University of Physical Education and Sport, Moscow,

Russia and Ph.D. Education - State University of Physical Education and Sport, Moscow,

Russia. Ksenia has participated in research support including:

PI: National Science Foundation MRI: Acquisition of a Vicon system for multi-disciplinary

research and education in rehabilitation engineering 2013-2016

PI: The US Department of Defense, Concept Award; 2010-2012; Design of Virtual Reality-

Based Therapy to Restore the Whole Body Coordination Deficits following Deployment-

Acquired Traumatic Brain Injury

PI: Blue Cross Blue Shield Foundation of Michigan, Research Grant; 2012-2013; Virtual

reality game–based telerehabilitation in patients with traumatic brain injury

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PI: The Association of Schools of Allied Health Professions - Interdisciplinary Research

Award; 2012-2013; Virtual reality game–based telerehabilitation in patients with

traumatic brain injury

Research Areas include the mechanisms of motor control and learning and their disruption

in patients with different neurological disease; the recovery and compensation of

sensorimotor functions after neurological injury with the use of new rehabilitation

techniques including virtual reality and biofeedback.

Joseph E. Langenderfer is a professor of Mechanical Engineering in the College of

Science and Engineering. Education includes Post-doc, University of Denver Computational

Biomechanics Lab, 2005-2007, Ph.D., Biomedical Engineering, The University of Michigan,

2005, M.S.E., Biomedical Engineering, The University of Michigan, 2002, M.S.E., Mechanical

Engineering, The University of Michigan, 2001, and B.S., Mechanical Engineering, The

United States Military Academy, 1992. Langenderfer has affiliations with the American

Society of Biomechanics; American Society of Mechanical Engineers; and Orthopaedic

Research Society with professional interests in computational modeling of muscle and joint

loads; stochastic biomechanics modeling; in vivo and in vitro experimental biomechanics.

Honors and awards include Engineer-in-Training, New York State, 1992 and Captain,

United States Army, Armor Branch, 1992-1999.

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Results

Effect of bras on subject performance velocity

When averaged across all trials and exercises, there were no differences in velocity

of subject performance with brassieres compared to Control and no differences between

brassieres (p=0.21) (Figure 2). However, subsequent analysis revealed that subjects

performed high knees 9% faster with Nike as compared to Control (p=0.01) but there were

no differences when compared to other brassieres or between other brassieres and

Control. For jacks, subjects performed the exercise 4% faster while wearing Adidas

(p=0.02) while no other differences were statistically significant. Interestingly, while

running, subjects performed the exercise 7% faster while wearing all bras (p=0.0001), but

there were no differences between brassieres. No significant differences in velocity of

performance were found for side twists and walking.

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Figure 2: Subject velocity (mean±standard error) while performing exercises and wearing brassieres (H- High knees, J-Jacks,R-Running 12 meters, S-Side twists, W- Walking 12 meters). Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

Effect of bras on vertical breast motion

Across all exercises, all bras reduced vertical breast motion in a statistically

significant manner (p<<0.0001) (Figure 3). For high knees, all bras reduced vertical motion

significantly compared to Control (F=12.4, p<<0.0001). Shefit provided a 38% greater

reduction on average in vertical motion for high knees compared to the other bras. The

following differences in the vertical motion were significant: Shefit reduced motion more

than Adidas (p=0.001), Nike (p=0.04), and Under Armour (p=0.02). Shefit showed a

tendency to reduce vertical motion more than Moving Comfort, though the difference was

not significant (p=0.10). When performing jacks, there were significant differences in

vertical motion between conditions (F=50.9, p<<0.0001); all brassieres significantly

reduced vertical displacement compared to Control (p<<0.001). Once again, Shefit

provided a significant reduction compared to other bras (on average 25% greater

H J R S W0

1

2

3

4

Subject Velocity

Mete

rs/S

ec

Control

Adidas

Move

Nike

Under

SheFit

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reduction). Shefit was better than Adidas (p<<0.0001), Moving Comfort (p=0.01), Nike

(p<<0.0001), and Under Armour (p<<0.0001). Likewise, Moving Comfort was better than

Adidas (p=0.04), Nike (p=0.005), and Under Armour (p<0.001) at reducing vertical motion

during jacks.

Figure 3: Vertical breast motion (mean±standard error) while performing exercises and wearing brassieres (H- High knees, J-Jacks,R-Running 12 meters, S-Side twists, W- Walking 12 meters). Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

While running, significant differences in vertical breast motion between bras were detected

(F=21.9, p<<0.0001), and all bras reduced vertical breast motion significantly (p<<0.0001).

Shefit was better than Adidas (p<0.01), Nike (p<<0.0001), and Under Armour (p<<0.0001)

at providing greater reduction in vertical motion (by an average of 35% more than these

bras), while Moving Comfort performed better than Under Armour (p<0.0001). For the side

twists, significant differences in vertical breast motion were detected between conditions

(F=3.87, p<0.01), with Adidas (p=0.01), Nike (p=0.05), and Shefit (p=0.003) significantly

reduced compared to Control condition, but there were no differences between bras.

H J R S W0

0.02

0.04

0.06

0.08

Vertical Displacement

Mete

rs

Control

Adidas

Move

Nike

Under

SheFit

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Lastly, for walking, significant differences were found (F=16.8, p<<0.0001); all bras

reduced vertical motion when compared to Control (p value from 0.04 for Nike to

p<<0.0001 for Shefit and Moving Comfort). Comparing between brassieres, SheFit reduced

vertical motion compared to Adidas (p<<0.0001), Nike (p<<0.0001) and Under Armour

(p<<0.0001) with a 34% greater reduction for Shefit on average compared to these other

bras. Moving Comfort was better than Under Armour (p=0.02) at reducing vertical motion

when walking.

Effect of bras on vertical breast bouncing (acceleration)

When evaluating the ability of bras to reduce vertical bouncing, it was determined

that across all exercises, all bras reduced vertical bouncing in a significant manner (F=38.8,

p<<0.0001) (Figure 4). On a pairwise basis, across all exercises, Shefit provided

significantly more reduction (p<0.01) in vertical acceleration (72% reduction) compared to

all other bras (on average, 44% reduction). For high knees, all bras reduced vertical breast

bouncing in a significant manner compared to Control (all p<0.0001). Shefit resulted in

significantly greater reduction in vertical acceleration (73% reduction) compared to all

other bras (45% reduction) (Adidas, p<<0.0001, Moving Comfort, p=0.002, Nike,

p<<0.0001, Under Armour, p<<0.0001). For jacks, there were significant differences in the

reduction of vertical bouncing provided by all bras compared to Control (all p<0.0001).

Additionally, compared to Adidas (p=0.03), Nike (p=0.007) and Under Armour (p=0.02)

Shefit provided on average 34% greater reduction in vertical acceleration, with no

difference between Shefit and Moving Comfort (p=0.90). For running exercise, Adidas

(p=0.002), Moving Comfort (p<0001), Nike (p=0.001) and Shefit (p<0.0001) all reduced

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vertical bouncing significantly when compared to Control. Pairwise comparisons between

bras during running found the only significant differences in vertical bouncing between

Shefit and Nike (p=0.04), Shefit and Under Armour (p<0.0001) and between Moving

Comfort and Under Armour (p=0.03). Compared to Nike and Under Armour, Shefit reduced

vertical bouncing 33% more than these two bras. When subjects performed side twists,

there were no significant differences between any brassieres or Control condition when

testing for differences in vertical acceleration. When walking, all brassieres reduced

vertical bouncing significantly when compared to Control. Shefit reduced vertical

acceleration by on average 26% more when compared to Adidas (p=0.0001), Nike

(p=0.0001) and Under Armour (p=0.0002), but not Moving Comfort (p=0.12).

Figure 4: Vertical breast bouncing (i.e. acceleration) (mean±standard error) while performing exercises and wearing brassieres (H- High knees, J-Jacks,R-Running 12 meters, S-Side twists, W- Walking 12 meters). Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

H J R S W0

10

20

30

40

Vertical Acceleration

Mete

rs/S

ec/S

ec

Control

Adidas

Move

Nike

Under

SheFit

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Effect of bras on side-side breast motion

Analysis of the lateral breast motion determined that all bras reduced side-side

breast motion in a statistically significant manner when compared to Control (all p<0.01)

(Figure 5). On an exercise specific basis, none of the bras reduced side-side motion in a

significant manner for high knees. For jacks, only Moving Comfort reduced side-side

motion significantly (p=0.03). With running, Shefit (p=0.01) and Moving Comfort (p=0.02)

reduced lateral motion significantly compared to controls, but there were no statistically

significant differences between any bras. For side twists, no bras reduced side-side motion

in a significant manner. Likewise, for walking, there were no significant differences in the

side-side motion of the breasts between any bras and Control condition.

Figure 5: Lateral breast motion (mean±standard error) while performing exercises and wearing brassieres (H- High knees, J-Jacks,R-Running 12 meters, S-Side twists, W- Walking 12 meters). Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

H J R S W0

0.01

0.02

0.03

0.04

0.05

Side-Side Displacement

Mete

rs

Control

Adidas

Move

Nike

Under

SheFit

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Effect of bras on side-side breast bouncing (acceleration)

When analyzing the effects of bras on the side-side bouncing of the breast it was

determined that across all trials and all exercises all bras reduced the outcome in a

significant manner (all p<<0.0001) with no differences between bras (Figure 6).

Figure 6: Lateral breast bounce (acceleration) (mean±standard error) while performing exercises and wearing brassieres (H- High knees, J-Jacks,R-Running 12 meters, S-Side twists, W- Walking 12 meters). Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

When analyzing high knees exercise, significant differences between all bras and

Control were detected (all p<0.0001) with no differences between bras. For the jacks

exercise, Adidas (p=0.005), Moving Comfort (p=0.0001), Nike (p=0.02) and Shefit

(p<0.001) reduced side-side bounce in a significant way, but no differences between bras

were found. For running, no differences in lateral acceleration were found between bras or

Control condition. Similarly, although Shefit reduced side-side acceleration more than

other bras when subjects engaged in side twists, the differences were not significant for

H J R S W0

5

10

15

20

25

Side-Side Acceleration

Mete

rs/S

ec/S

ec

Control

Adidas

Move

Nike

Under

SheFit

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Shefit or for any bras. Lastly, for walking exercise, no significant differences were found in

side-side bounce.

Subject perception of bra comfort and performance

The subjective rating of each brassiere revealed no significant differences between

brassieres when subjects were asked to rate each brassiere for comfortability (Figure 7).

Figure 7: Subject ratings of each brassiere on a 0-10 numerical visual-analog scale. 0 represents comfortable (no pain), 5 represents uncomfortable, and 10 corresponds to painful. There were no differences in subject ratings of the brassieres in terms of comfortability. Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

Subject answers to the question of which brassiere felt and/or performed the best

revealed that subjects preferred the Shefit bra by a nearly two to one ratio. (Figure 8).

Likewise for the question regarding ease of putting on and taking off the bras, subjects

rated Shefit as easiest by a nearly two to one ratio (Figure 9).

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Figure 8: Subject answers to the question: “Which bra felt and/or performed the best?” More subjects rated Shefit as the best bra by a nearly 2 to 1 ratio. Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

Figure 9: Subject answers to the question: “Which bra was easiest to don/doff?” More subjects rated SheFit as easiest to put on and take off by a nearly 2 to 1 ratio. Control was natural (no-bra), Move – Moving Comfort, Under- Under Armour.

0

1

2

3

4

5

6

7

8

9

10

Nu

mb

er s

ub

ject

s re

spo

nd

ing

Adidas Move Nike Under SheFit

Which Bra felt/performed best:

20

Discussion

This study measured the performance of the Shefit brassiere at reducing breast

undesirable and uncomfortable breast kinematics when subjects engaged in 5 common

exercises and compared the resulting reduction in displacements (motion) and

accelerations (bouncing) to that encountered while the same subjects wore four similar

competitive sports bras. For most performance outcomes, the Shefit bra reduced kinematic

outcomes more than the other brassieres. In addition, across the outcomes and directions,

Shefit generally reduced the undesirable motion and bouncing more consistently than the

other bras. In particular, for vertical displacement and acceleration, across all exercises,

Shefit resulted in the greatest average reduction compared to the other bras (Figures 3 and

4). For lateral (side-to-side) outcomes, Shefit was less consistent and did not always reduce

motion and bouncing more than the other bras, although Shefit still performed quite well

on average (Figures 5 and 6). When subjects evaluated performance of the brassieres in

terms of comfort and ease of use, Shefit was rated better than the other bras in terms of

performance and ease of use, but there were no differences in terms of how the bras felt or

in terms of pain and discomfort.

In summary, the results of this study suggest that the Shefit bra is very effective,

performed quite well, and very consistently reduced motion and acceleration in the vertical

direction. However, the Shefit bra is somewhat less effective, and somewhat less consistent

at reducing displacements and bouncing in the lateral direction. This finding means there is

potentially some room for future improvement perhaps in the design of the brassiere to

improve bra performance in reducing undesirable kinematics in the side-to-side direction.

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Acknowledgements

This project would not have been possible without the immense contributions of Nilanthy

Balendra, M.Eng. Research Engineer, Motion Analysis Center, and Taylor Gibson, B.S.,

Physical Therapy graduate student, who were intimately involved in subject recruitment,

testing and data processing.

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References

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kinematics of the breast during a two-step star jump." Journal of Applied Biomechanics 26:

465-472.

Cai, Y., L. Chen, W. Yu, J. Zhou, F. Wan, M. Suh and D. H. K. Chow (2018). "A piecewise mass-

spring-damper model of the human breast." Journal of Biomechanics 67: 137-143.

Lorentzen, D. and L. Lawson (1987). "Selected Sports Bras: a Biomechanical analysis of

breast motion while jogging." The Physician and Sports Medicine 5(15): 128-139.

Milligan, A., C. Mills, J. Corbett and J. Scurr (2015). "The influence of breast support on

torso, pelvis and arm kinematics during a five kilometer treadmill run." Human Movement

Science 42: 246-260.

White, J. L., J. C. Scurr and N. A. Smith (2009). "The influence of breast support on torso,

pelvis and arm kinematics during a five kilometer treadmill run." Ergonomics 52(4): 492-

498.

Wood, L. E., J. White, A. Milligan, B. Ayres, W. Hedger and J. Scurr "Predictors of Three-

Dimensional Breast Kinematics during Bare-Breasted Running." Medicine and Science in

Sports and Exercise 44: 1351-1357.