Optimising the design of sports bras: Part I Ankit Intelligence

This report provides an introduction to the market, including forecasted growth over the next five years, before exploring the typical design components of sports bras and how they work to support the breasts during activity.

1. An introduction to sports bras

Sports bras, if the correct fit and style for the wearer and activity, play an essential role in stabilising the oscillation of the breasts during dynamic movement and subsequently, minimise the risk of discomfort and even physical harm. Research indicates that sustained loading stress to the core structural supports of the breasts, Cooper’s ligaments, can result in pain and the possibility of breast sagging, which can also lead to emotional distress [1], [2]. Moreover, a lack of adequate support has also been shown to be a deterrent to participating in sports and exercise; being unable to identify a suitable sports bra was found to be the eighth highest perceived barrier (of 24) to sports and exercise participation [1]. Studies have also identified that some women have refrained from physical activity specifically due to pain and/or embarrassment caused by excessive breast movement [1], [3]. Furthermore, this issue is indiscriminate of age, as both younger and more mature age demographics report facing such issues. For instance, adolescent girls identified experiencing backache, breast pain and even ridicule from classmates within academic settings borne from the issue of pronounced breast movement during physical activity, damaging self-esteem, adversely affecting body image and ultimately affecting their willingness to participate in sport [2], [4].

Notably, there also appears to be barriers for many receiving professional fit advice, perhaps also spurred in some instances by these same feelings of self-consciousness or insecurity. This is likely exacerbating the proportion of women wearing the incorrect bra size – believed to be as high as 76 to 86% of bra users [5]. In one study conducted in 2014, 54% of survey participants (conducted with women who ran the 2012 London Marathon) reported having not attended a professional bra fitting in the last year [6]. However, compounding upon the issue of poor sports bra fit in particular, more recent research published in 2020 by members of the Research Group in Breast Health indicates that consumers are even less likely to have been professionally fitted for a sports bra, with 65.6% of US-based participants reporting to have never utilised such a service [1]. These issues with fit and a general lack of consumer education and confidence on the topic perpetuates an experience of ill bra fit, incorrect sizing and breast discomfort, contributing to the perhaps surprisingly low rates of sports bra uptake during exercise seen in a number of global populations. For instance, a study looking specifically at a Chinese survey population found that only 40% of the participants had ever worn a sports bra, with usage influences including the monthly income and breast size of the respondent [5].

1.1. Market potential

Numerous studies such as these have subsequently recommended better educating consumers – irrespective of their socio-economic position – on the importance of appropriate support during exercise. And indeed, wider breast health, in a bid to remedy identified issues, such as emotional and/or physical discomfort engaging in physical activity.

Consumers also appear to have shifting priorities in the characteristics of their day-to-day bra purchases, listing ‘comfort’ and ‘support’ as primary to aesthetically-driven influences, according to a report by The NPD Group; this could be correlated with reports of falling sales of volume-enhancing bra styles, commonly referred to as push-up [9], [10]. These factors have seen not only increasing product weighting from sports brands in their provision of sports bras, but more fashion, lingerie and loungewear brands entering the space, who have been able to capitalise on the rise of athleisure to provide more athletic and trend-focused bra styles [10]. Furthermore, bras are increasingly available through a number of distinct channels, including ecommerce, brand stores, supermarkets and speciality stores (such as sports stores or lingerie boutiques), with physical retail locations also housing complementary services such as specialist bra fitting appointments and personalised style assistance [8].

Crucially, across all channels, close to US$7.2bn was reportedly spent on bras within the US between May 2018 to 2019, with over a quarter assigned to the purchasing of sports bras [9]. In a survey conducted by The NPD Group, the number of consumers reporting to have shopped for or purchased a sports bra rose 7% from 2015 (38%) to 2018, settling at 45% of participants [9]. As also previously discussed, one barrier to further market engagement is that not all women use sports bras. So efforts to further educate the audience on the importance of proper support during exercise may nurture a wider pool of prospective consumers.

2. Fundamentals of adequate breast support in bra design

Like standard, everyday models of bras, sports bras typically contain a number of design elements to supplement their ability to lift, support and shape the bust. However, sports bras perform this function to a greater intensity with the specific aim of containing the breast to neutralise severe breast movement and subsequent mechanical strain during dynamic movement. The intension is ultimately to shape and compress the form to make the breast volume more manageable during exercise. This is achieved through stabilising and securing the breast close to the chest wall, as this ultimately minimises the potential to generate momentum independently of the torso – an event which can cause great discomfort. To achieve these effects, there are a number of complex mechanisms implemented within the pattern design and construction of bras which contribute to better breast movement control.

To provide insight on these construction elements, WTiN speaks with Catherine Livingstone, a lecturer on the Contour Fashion programme and lead of the newly established Contour Fashion Innovation postgraduate course at De Montfort University, Leicester, and Brogan Horler, a senior research associate for the University of Portsmouth and the Research Group in Breast Health (RGBH), who conducts both research-focused and commercial investigations into the performance of sports bras.

De Montfort University: Contour Fashion
De Montfort University’s Contour Fashion specialism has traditionally been associated with and served the niche of lingerie and swimwear design. In recent years, a heightened interest in sportswear has been acknowledged in the ‘intimates’ market, with a number of lingerie labels entering the space alongside dedicated sports brands.

As such, the course appears to be increasingly training its student cohort on the design and development of sports bras alongside a traditional focus on swimwear and lingerie. Meanwhile, Livingstone says the addition of the postgraduate course looks to provide a platform for intensive innovation specifically within the field of contour-specific products. It spans lingerie, swimwear and sportswear for a wide range of applications including performance apparel, but also medical garments and wearable technologies.

University of Portsmouth: RGBH
Elsewhere, the University of Portsmouth, and more specifically, the RGBH, has provided a wide catalogue of scientific literature on the topics of breast health, breast biomechanics and sports bra design. It’s also a recognised academic touchpoint within the industry. Focusing on the metric of breast movement reduction (%) as a means of assessing sports bra performance, the group provides the industry with independent bra testing services which enables manufacturers to prove their products.

In addition to working directly with industry players, the group’s members work on a number of topics within the field of breast health. Most recently publishing a paper attributing identified performance gains to specific, independent design variables. In addition, the group has worked to provide educational materials for women and primarily school-age adolescents to assist in better educating females on breast health, bra fit and the types of bras suitable for activity to encourage greater rates of correct sports bra usage and subsequent sports participation.

2.1. Similarities between sports bras and fuller bust fashion bras

As discussed, the differing requirements of sports bras from conventional bras entails an enhanced focus on breast containment, shaping and lift to enhance the level of support achieved from such garments. Due to these aims, Livingstone believes much of the intricacies of fuller bust design also translates into the design of sports bras: “I do think there are similarities between sports bras and fuller bust bras generally, because with sports bras there is more movement, so the underband is under more pressure for that reason,” she says. “With fuller bust bras there is more weight, more mass, so again the underband and all aspects of those bras are under more pressure.”

Echoing this sentiment, to contain, accommodate and support the breasts sufficiently during prolonged physical activity and therefore probable excessive breast movement, a sports bra may have a higher centre front (CF), more intensive or wider underband features, thicker shoulder straps and higher coverage cups. Namely, the fundamentals and objectives leading the design of effective sports bras largely mirror those employed within support-focused fuller bust styles of bras.

Alternatively, as well as design and fit considerations, materials also play an important part in delivering stability and breast control for both these bra categories. Livingstone says: “Having a powerful, firm fabric on the cup and a really strong mesh or a strong underband elastic around the body will really help support the breasts. And that’s more important for larger bust sizes.” Likewise, these qualities can greatly assist in stabilising the breasts during exercise, regardless of wearer size, as rigidity in the cups reduces the potential for the material to be manipulated and stretched by the breasts’ movement during activity.

Of course, fuller bust sports bras are also a distinct subset within the market. However, as there is a consideration of a greater breast volume within this category, the type of sports bra, irrespective of other design variables, also has a more significant influence on breast control performance than when supporting smaller breast sizes. Specifically, these three core types of sports bras are identified both in academic and commercial spheres as compression, encapsulation, and combination/hybrid bras, and as will be further explored in Section 3, the principles behind encapsulation and combination-style sports bras mirror many aspects of fuller bust design. Bras triumphing the encapsulation style in particular will clearly separate and suspend the breasts in independent cup structures, while often employing more comprehensive cup coverage, rigid materials and intricate cup structures than their solely compression counterparts, much like supportive fuller bust fashion bras.

“That’s why encapsulation bras tend to work better for larger breasted women, because they are lifting and holding each breast and trying to hold it in place,” says Horler, who contributed to a recent study identifying the encapsulation style as the most effective design variable regarding breast movement reduction within the design of sports bras.

“What tends to be apparent in those sorts of styles is that the cup isn’t as stretchy – it’s more rigid – so it’s able to control the movement a lot better,” she adds.  As such, and by design, the similarities between fuller bust bra design and the design of sports bras are particularly evident in the development of fuller bust-specific sports bras.

2.2. Underband

A fundamental design aspect within the support functionality of bras – whether fashion or sports-orientated – the underband plays a central role not only as a hub for the construction of other bra structures, such as the cups, but as the key stable contact point between garment and body. Spanning the entire length of the bra’s bottom edge, the underband may be comprised of a centre front, cradle and wings. Or alternatively, a single, solid pattern piece or elastane trim – with this second approach particularly common in the design of sports bras. Additionally, the underband may either be closed, or opened and fastened with a component, commonly either a zip or hook & eye, to provide ease to the process of donning and doffing.

Assuming a role akin to a cantilever element seen in architecture, whereby a load that extends horizontally is supported sufficiently by a structure secured only at one end, the underband acts as the firm foundation for the bra by providing the required anchor point from which to adequately support the breast volume projecting away from the chest. As such, to ensure effectiveness – particularly in bras designed for larger bust sizes or activities prone to excessive breast movement – the underband should be designed and worn perpendicular to the ribs to ensure the greatest stability and tension around the torso.

“The underband is critical as it provides that anchorage of the bust,” says Livingstone. “It gives grip around the ribcage and provides that fundamental support for the rest of the bra. So, if that’s in motion, or not on straight – it’s slightly angled – then it’s not going to provide that true anchorage.” Therefore, a rising or sloping fit on the wearer, identified through either a low or high fit across the back, can disrupt the balance of the garment, instead distributing the weight of the breasts to other zones.

A critical area that can be particularly affected in the case of an ineffective underband includes the straps, which are primarily intended to keep the bra and cups secure against the body rather than provide any additional support. While efforts can be made to reduce the potential for shoulder discomfort, through the configuration of wider straps or padding for instance, a greater than intended load on the shoulders can cause unpleasant pressure points. This has been specifically identified in a number of academic-led enquiries into the satisfaction and sentiment consumers feel towards sports bras, which have shown that the sensation of straps which ‘dig in’ can be a significant comfort issue, even potentially deterring sports bra use altogether [1], [3], [13]. This ultimately illustrates the importance of a stable and secure underband to achieving a comfortable yet supportive and functional sports bra.

However, regardless of the underband’s positioning, it will also not perform optimally unless under sufficient tension around the wearer. “With the movement of the body, the underband is more likely to move on the body as well, so regardless of whether it’s on an angle or not, that underband is under more strain through that movement,” says Livingstone. “The bra may move onto the breast tissue itself… or it could shift around the body. This means the cups containing the breasts aren’t positioned correctly, so the cups won’t be supporting the bust from the right position.”

Therefore, the underband configuration of particularly supportive sports bra styles may have a greater underband width or alternatively, exhibit a firmer stretch to ensure it recovers tight to the body – as is often utilised in larger bust sizes within the lingerie market. This gives the sports bra the greatest prospects of gripping and stabilising onto the ribcage, and generally withstanding the stress the bra encounters during physical activity. Therefore, when assessing the fit of a sports bra style during development, the test wearer should ideally be wearing the bra on the loosest possible level of underband adjustment, such as the last row of hooks on a hook & eye closure, and be able to fit approximately two fingers between the underband and body with relative ease [14]. Any looser or tighter may indicate a potential lack of support or cause of discomfort respectively, which may worsen over the use of the garment. Livingstone notes: “If you’re already at the tightest adjustment and there’s nowhere further to adjust to, over time, when your fabrics and elastics wear and give, it’s harder to maintain the efficacy of the bra without that further adjustment.”

2.3. Sizing and fit: Alpha and traditional bra size scales

In addition to the support and functionality, the underband is also critical to the sizing of the garment, representing the numeral component in traditional bra sizing. This methodology offers two sizing metrics in the band and cup respectively (please note sister sizing, which will be explained in Section 3), allowing for the provision of greater sizing increments and therefore the variation to provide more varied fit to a wider range of consumers.

Notably, Horler has observed through testing and assessing an array of sports bras from different manufacturers, that those produced by lingerie brands often retain the use of traditional bra sizing (34B etc), while sports brands appear to regularly utilise alpha sizing (S, M, L). “Bras that come from lingerie brands tend to really fit well … because they are offered in band and cup sizes like you would your everyday bra,” says Horler. “Because there are more options along that sizing scale, particularly for women who are larger breasted, they can adjust the band and cup size and then make sure they find a good fit.”

Offering band and cup sizing is also particularly beneficial for consumers with disproportionate band and cup sizes – such as a small back paired with larger cup sizes, or vice versa – as alpha sizing is instead likely to utilise proportional grading between XS and XL, for instance. This accommodates the scenario of a larger garment size equating to both larger cups and a larger band, however, may diminish the prospect of finding a well-fitting bra for consumers outside of this anatomical ideal. “You’ll find that some women probably need a large for the cup volume, because they’re a larger breasted woman, but they may be a really small band size,” adds Horler. “So that extra-large band size is going to be much too big. So, for those sorts of sizes, the alpha sizing doesn’t tend to work as well.”

Due to these complexities affecting bra design and the immense anatomical variation in consumers – extending to variables such as body length and breast spacing – Livingstone believes alpha sizing in particular may be more difficult for consumers to size correctly. “Your pool of averages in terms of size and fit [with alpha sizing] becomes quite wide,” she says. “If you’re used to looking at a band size and a cup size, it can be quite difficult to accurately assess where you are, and if you’re buying a medium bra, [it can be difficult] to understand whether you fit into that.”

As such, while alpha sizing allows for fewer sizes per style, depending on the core consumer group (which will be discussed further in 2.5) and type of bra elected (compression, encapsulation, combination), such a sizing strategy may ultimately disenfranchise consumers who do not align with the average body captured in each sizing step, ultimately leaving those with proportions uncatered for with less choice of product or potentially completely excluded from a particular brand [15]. Nevertheless, Livingstone believes the number of manufacturers active in this space provides that diversity of fit required to cater to different consumer groups. “The multitude of brands actually offers that choice, which is probably quite necessary to fit those different demographics that we have,” says Livingstone, noting that brands may also employ distinct and consistent sizing to secure consumer loyalty – a strategy particularly utilised by lingerie labels who also offer every-day and speciality (maternity, adolescent, pro-surgery) styles in addition to sports bras, and thus can be sized consistently throughout.

Alternatively, alpha sizing may be perfectly applicable in some design scenarios, specifically for compression styles which do not exhibit separate cup structures and demonstrate high levels of stretch and recovery to provide support – widening the size applicability of the garment. This allows the garment to adjust to the form of the wearer, and the need for a specific user to size up is largely identified solely by the sensation of excessive tightness on the body or inhibitability to wear the garment correctly. Therefore, the grading employed should consider the intended consumer group and type of bra so not to inhibit the commercial success of a style – for instance, employing more accurate band and cup sizes for fuller bust encapsulation sports bras and alpha sizing for bras intended for smaller cup volumes, where adequately controlling breast movement can be achieved without anatomically-reliant cup structures.

2.4. Shoulder straps

As discussed, a wearer can encounter both fit and comfort issues if there is a lack of synergy between the underband and shoulder straps. An incorrect distribution of the breasts’ weight across the bra or lack of strap stability on the shoulder can result in unpleasant pressure points on the body or disruptive bra wear respectively, hampering the wear comfort. Notably, slipping or cutting into the shoulder were explicitly found to be two of the most common deterrents to wearing a sports bra in a survey of Australian consumers, highlighting the critical nature of strap comfort [3]. As such, firm and stable straps should be a pivotal focus within the design of a sports bra. “If straps are too loose they’re likely to fall off the shoulder, and also they’re more likely to rub through movement,” says Livingstone. “If your strap is nice and firm against the body, they’re more likely to move with your body.”

As such, crucial to delivering undisruptive straps is their configuration and positioning, with cross straps and racer style straps enabling higher positioning on the shoulders and therefore minimising or eliminating the potential for slippage. Furthermore, as these straps typically lay either more centrally or further from the arm drop than standard lingerie straps, these particular configurations can be far more ergonomic during certain activities, such as tennis, climbing or basketball, which all demand pronounced range of motion in the arms. As such, anchoring the straps closer to the neck and more central on the back minimises the plausibility of the bra disrupting activity either through strap slippage or disruptions to mobility.

Due to the benefit this grants to consumers, styles with straight straps may include a fastening component which enables the straps to be held together at the back, or even feature removable back strap clips to allow adaptable strap configuration. As adjustability enables greater customisation of fit, such allows consumers to better accommodate the garment to their specific build, form and even activity. Notably, adaptability in the strap configuration may also assist in prolonging the bra’s wear lifespan, as when the fit and shape begins to deteriorate – from the elastane content loosening over use, for instance – and the support of the breasts lessens, reconfiguring the straps can redistribute any slack in the straps by redirecting its shape across the wearer’s back.

“With lots of sports bras, if they’re not a racerback there’s actually a mechanism on the back straps so that there can be a dual effect strap. You can either have it as a standard straight-back strap or you can fasten the straps together to create a racerback fit,” says Livingstone. “That can actually help with the lifespan of the bra as well, as when the cups start to wear and loosen, by actually repositioning your straps together in that racer position, it adds a bit of uplift – a bit of support.”

The position from which the strap is joined to the garment also contributes to its stability, as well as the stability of the breasts. This is referred to as the apex point, which in the design of sports bras, is prominently more centralised than standard bra styles. This grants both shoulder positioning further from the arm – therefore minimising strap slippage – and an apex better aligned with the nipple point, which can contribute to better balanced breast support. “With sports bras, the position [of the apex] is generally slightly more inwards on the body, so it’s more central to the actual bust point,” Livingstone explains. “That provides a more centralised support, whereas if your apex is offset to one side, a greater proportion of the top cup is unsupported.”

Sports bras may also differ from everyday counterparts in the precise location of the apex on the body. With a large number of conventional fashion bras, the strap is comprised of a strap elastic attached to the highest point of the cup, with the width of the elastic perhaps dependent on the garment size. As discussed with the underband of fuller bust sizes, the straps may also utilise a wider variant of an elastic to better distribute any pressure experienced on the shoulder. As the load supported by a sports bra during activity is also affected by dynamic movement, regardless of size, many designs feature textile straps over the shoulder, and instead, transition to conventional elastics on the back of the body. This provides the opportunity to integrate padding (preferred by 42.8% and 51.2% of US and UK consumers, respectively) or further widen the strap over the crest of the shoulder – mitigating the commonly identified issues of chafing and ‘digging in’ by supplying a greater surface area to dissipate the strap pressure across [1], [6].

Nevertheless, accommodating a greater proportion of the shoulder strap length with textile is often is at the cost of adjustability, as the elastics are the components hosting adjusters to enable length changes. With less elastic available to be fed through the adjuster, there is less capacity for overall strap adjustment. “I think that actually is quite an interesting area in sports bras in terms of where potential lies to improve,” says Livingstone. “It’s quite difficult as you can absolutely see there’s a benefit in having those wider straps and having padding as well to add to comfort, but actually the adjustability is very important.” This  sentiment on the significance of adjustability has been echoed in a number of academic works into the area of sports bra design, noting that strap, and indeed underband adjustability, can have some influence on breast movement control, or at the least, grant accuracy in adjusting a bra fits to differing breast and body forms – crucial as secure fit enables the bra to offer an optimal range of breast support [2], [13], [18].

2.5. Cup structures and neck edge depth

Cup structures inform the support, coverage and form of the breasts, and therefore the aesthetic quality in the shaping provided to the bust is also often a consideration for consumers. In addition, consumers may be looking for specific characteristics such as nipple concealment, breast minimising qualities and greater breast coverage, which will be driven by the design and application of the bra’s cup.

In addition to the cup’s structure and shape, the neck edge is particularly important to the support credentials of all types of bras. However, in the context of sports bras, a recent study conducted by the Research Group in Breast Health indicated that the neck edge depth ranks fifth in terms of performance significance. An analysis of design variables from the study identified that for every centimetre added to the height of the neckline, the breast movement reduction rate increased by 0.75%. “That wasn’t really a surprise to us actually,” says Horler, who co-authored the study, “because within the scientific literature, a high neckline is recommended for better support. And the premise behind that is that higher neckline enables you to encase the entire breast tissue within the bra.”

Livingstone confirms this sentiment: “Sports bras that are plunging – which are found more with fashion brands – are banking on the wearer using the bra as a fashion commodity rather than a support garment,” noting that a plunging style will only provide sufficient breast control and coverage for a subset of users. These include those with breasts naturally less susceptible to breast movement or women engaging in particularly low impact sports, and as such, appropriate cup structures and neck edge depths may be determined by the target consumer of a particular bra style, or indeed, the manufacturer itself. Those appealing to younger consumer demographics may focus on aesthetics and style – especially in the low impact category – primarily over a highly intensive support function.

The latter is often considered to give a more rounded, smooth and modern breast silhouette. But it potentially lacks the same precision fit of seamed cups, as each individual pattern piece forming these cups delivers greater shape dimension to mimic the natural shape of the breasts. However, seams lines can potentially show under clothing and alternatively, may be a source of chafing against the sensitive breast tissue if the cup is not lined or the seams are insufficiently taped.

The materials affiliated with each construction methodology should also be considered, with cut and sew offering the potential to use particularly rigid fabrics, especially in key zones such as a cup sling or cup upper panel, to manipulate and centralise the wearer’s breast tissue and subsequently minimise movement potential (discussed further in 3.1). This also identifies that moulded cups are therefore particularly reliant on not only the shaping assumed but the stability of the material used, as there are less structural elements than cut and sew styles to assist in retaining its form over time. “Moulded cups can equally be very effective, and it really depends on the fabric that’s being used as well, because that support and structure will equally come from the fabric,” says Livingstone.

However, Livingstone also notes that a combination of both cup construction methodologies – found particularly in encapsulation and combination styles of sports bra – can be particularly advantageous to the comfort of subsequent sports bras. “What I’ve found is quite nice with [more contemporary] sports bras, is that they often have moulded inners. So, they might have a cut and sew outer cup, but by having a smooth moulded inner cup, it creates a slippery layer between the breast tissue and those seams.” Notably, an investigation into the purchase inclinations of groups of US, UK and Chinese regional consumers demonstrated that padded or moulded cups were largely preferred across all three populations [1]. Therefore, the layering of both cut and sew and moulded cup components may possibly allow for both preferred moulded cup interiors – delivering on a minimised risk of chafing and irritation – while the outer layer can consist of more rigid elements to effectively compress and contain the breasts.

2.6. Wires

Wires appear a polarising topic in the discussion of both sports bra and everyday intimates design, with debate into the effectiveness and comfort of underwires in modern bra design. Designed and implemented properly, the wire is intended to trace the breast root of the wearer – the point under the breast volume whereby the chest and breast tissue meet, to issue support to the above breast tissue. “The wires should sit quite flat against the breastbone and be fully behind the breasts at the side as well as under the arm. Obviously with movement, if they were in the wrong position to begin with, there’s more room for them coming onto the breast tissue or digging in painfully,” says Livingstone. This likely contributes to complaints from consumers regarding wire discomfort [1], [6].

However, as the breast root can differ largely across the female population, a particular wire model may only be suitable for a proportion of women and thus cause fit or discomfort issues for others. Again, some diversity is provided with the volume of brands within the market, as each is likely to utilise a consistent selection of wires throughout either certain bra categories or an entire portfolio. As a contributor to fit and lift, consistent wires provide a foundation for consistent cup design, and in turn, helps establish a distinct brand fit which can nurture a base of loyal consumers.

Nevertheless, as wires do influence the style and fit of a bra, its presence may be fit disruptive if the wearer’s form does not reflect that imposed by the wire. While the wire is designed to open into place when pulled by the wing during wear, its rigid nature is ultimately essential to its supportive performance. Therefore, a particularly deep, narrow wire style cannot readily adapt to alternative breast shapes, and thus is unlikely to align with a shallow, wide breast root – and vice versa – procuring fit issues for an incompatible breast form, regardless of cup size (see Figure 6). “It’s very difficult to get a one-fit fits all at this moment in time, whereas the multitude of brands at the moment sort of offer that choice,” says Livingstone. “Every brand has a particular consumer, and every brand has a particular fit that they try to stay loyal to.”

Nevertheless, in addition to requiring a good fit harmony between body and garment, some women may also be particularly sensitive to the sensation of a wired bra against the body. ‘Underwire digging’ was found in a study to be the only bra issue that didn’t correlate with breast size, while other issues appear to be exacerbated when there are greater demands on the bra – with more frequent issues found in larger cup sizes [6]. Following this, in the specific context of sports bras, unwired styles were found to be preferred by US, UK and Chinese consumers irrespective of breast size [1]. As such, wires may be more appropriate in certain sports bra categories, as Livingstone notes: “If the bra is wired – which for fuller busts, it would offer more support – because of the friction placed on the body through exercise, then significant protection in terms of that wire casing is really quite important. Probably more so than with a smaller size, just because of the strain, pressure and friction that is undergone on a larger size.”

2.7. Material selection

As will be discussed further in Part II of this report series, material selections have also been an area of focus within the study of the design and performance of sports bras. As with the design of particularly ergonomic garments – as previously discussed in the context of cups – the degree of stretch found in each area of a garment may strategically differ to provide tailored performance. This approach is often found in the design of everyday fashion bras, as a stretch mesh will likely be adopted across the wing to enable stretch around the body, while the cups exhibit a firmer structure to grant robust support of the breasts.

Sports bras may also utilise such a design strategy, using material selection as a means of providing greater movement cooperation in the torso – crucial during the increased rate and depth of breathing during exercise for instance – while retaining control in the front of the bra. “It’s a balance between the fit, design and the pattern making of designing that product, and the fabric which is used,” Livingstone notes. “Often a sports bra may have some stretch on the outside of the cup, but generally, the supportive structure is quite rigid really, and then the stretch will come from around the body – on the wing and back sections – where you obviously need movement to carry out those sports. But the movement won’t actually be in the cup itself.”

Rigidity in the bra’s structure has also been supported by numerous scientific papers examining sports bra design, as it allows for greater compressive support and inhibits the cup stretching with the momentum of the breasts during dynamic activity [18], [23]. For instance, nylon featuring as a sports bra’s principal fibre content was deemed to have a greater bounce movement reduction rate, identified through stepwise procedure analysis, than polyester; specifically, a change from polyester to nylon as the primary fibre source was attributed to a 3.39% increase in the rate of breast movement reduction. “Nylon tends to be a stronger fabric,” says Horler, “so that’s why we think that that would perform better because… it’s more rigid and able to control the movement of the breast better.”

“From the sports bra brands, we tend to see lots of innovative designs and really clever materials that are now coming into sports bras,” she says. “So you’ve got your standard moisture wicking fabrics but we’re also seeing [developments like] fabrics that have a motion sense technology, where if you’re just lifting weights the bra will be a little more relaxed. But if you’re going to go for a run it will be a firmer fit… so we’re seeing lots more clever fabrics from sports apparel brands.”

3. Considerations towards fit, sizing, performance and consumer education

Crucially, determining the appropriate level of support for any such wearer may involve numerous factors, however, the size of the breasts can be a key indicator as to the most suitable style for an individual. This is due to the breast movement control attributed to each of the three core sports bra types across the diversity of bust sizes. Nevertheless, the activity in question also has ramifications on the level of support required. For instance, studies analysing the kinetics of specific movement sequences, such as walking, jumping and running, have identified the latter as having the greatest loading strain on the breasts [6]. As such, activities requiring similar intensities of dynamic movement will likely require the use of more comprehensive breast support, which for many users, particularly those with a greater bust size, will take the form of an encapsulation or combination bra over a compression style, due to the mechanics of how different types provide support to the breasts.

Crucially, as discussed, consumers distinguishing styles and fits suitable for their specific needs appears a prevalent challenge hindering the market, as the majority of consumers are already wearing bras of the incorrect size (with a lower boundary estimated to be 70% of women)  [1], [5], [25]. This may correlate with the rate of women utilising professional fit services, with one study identifying that almost a fifth of consumers have never been fitted professionally [6]. This extends further when looking at the fitting of sports bras specifically, with 61% of a UK pool of consumers and 66% of US participants identified as having never been professionally fitted for a sports bra; alternatively, Chinese consumers were more likely to have engaged with such services, with only 22% reporting to have never received a professionally derived size [1]. Notably, per Google Trend analysis, the search frequency for ‘Bra size’ witnessed rapid growth in the first two quarters of 2020, perhaps correlating with the introduction of more stringent and national-level lockdowns, as can be observed in Figure 8 [26]. According to the platform’s chart graphic, the peak in search popularity across a period of January 2016-2021 occurred between 7 and 13 June 2020, however high search numbers are observed cluttered around the midpoint of the year, with a decline occurring through August and September.

Figure 8: Google Trend data for the interest over time concerning the search term, 'bra size' [26]

Notably, the more specific search term of ‘Sports bra size’ also saw a similar spike in interest over the same period as the former – with search frequency again peaking in June 2020 [27]. Interestingly, those completing this search were also searching for a number of related queries at a breakout rate, which, per the platform’s own presentation of the data, means that the increased search frequency and relationship between the original search and these other search terms is unprecedented. Among them include precise fit and size enquiries, such as ‘does a sports bra reduce breast size’ and ‘plus-size sports bra high impact’ – the latter demonstrating a +950% increase in paired search frequency with ‘sports bra size’ – which may indicate that consumers are actively seeking fit guidance specific to their needs.

Figure 9: Google Trend data for the interest over time concerning the search term, 'sports bra size' [27]

While there may be other influencing factors for an increased rate of independent research into bra sizing, perhaps one trigger has been the inability to access professional fit services, as physical retail locations in many regions have not been permitted to be consistently open to consumers over the past year. As such, when purchasing bras online, there is a possibility that consumers are instead relying on fit guidance supplied directly by the brand or retailer, or independent guides found through such searches.

“I do think consumers struggle,” says Horler, who through the work of the RGBH, regularly consults brands on how to improve the performance of their sports bras. “The big issue is probably more to do with sizing and fit, so women will see a bra they like online, think, ‘right I’m going to be doing running, so I need this high support sports bra, I’m this size, I’ll buy it’. But they might get it home and it’s not performing for them.”

“From an education perspective, there is definitely more that could be done,” she continues. “Like our bra characteristics paper…”, which will be explored thoroughly in Part II of this report series, “that’s only something [the RGBH] ourselves recently found in what to look for in a high support sports bra, so it’s up to us to work with brands and communicate that to the consumer.” More precise and in-depth tools and resources on fit may therefore be particularly well received by consumers as the restrictions on physical retail hopefully ease over the coming months. Perhaps interesting and engaging fit experiences instore can also empower consumers to make informed purchase decisions, ensuring that a sports bra aligns with their precise needs and displays all indications of true supportive fit.

3.1. Ideal sports bra performance

Bras, whether fashion or functional, manipulate the breast tissue to support, lift and shape the breast tissue. The precise objective of supportive sports bras is to centralise that tissue, rather than primarily support from the sides or enhance the bust, to minimise the capacity of movement through vertical, horizontal and diagonal planes. Holistic containment is particularly critical as the breasts move independently from the torso, which during physical activity is further exacerbated; the delay between the movement in the body corresponding to motion of the breasts means there is a lack of synchrony.

As excessive breast movement can be disruptive and uncomfortable across the spectrum of breast size, these principles hold relevance to both more movement-vulnerable larger bust sizes, but also the design of bras for older consumer demographics and those aimed at medium and high intensity activities, which all demonstrate heightened risks of breast motion.

3.2. Compression, encapsulation and combination/hybrid bras

As discussed, compression bras are a particularly common style of sports bra which contain no constructive elements or structural supports to shape and contain the breasts individually. Rather, compression bras work to perform that exact function, by compressing the breast tissue to the chest wall and subsequently reducing the breast projection and therefore the potential for excessive breast motion. Due to the need to compress around the torso to keep sufficient tension, compression bras typically feature no closure system, and rely on the stretching capabilities of the garment to allow for dressing over the head. This has two resulting concerns which may affect the bra’s support capacity, especially over the course of its use life.

First, with no closure, the bra must stretch the width of the shoulders to allow for dressing. To grant breast support, the bra must then fit firmly against the torso. Over time, the cycle of dressing and use ultimately deteriorates the quality of the elastane, dampening the bra’s potential to provide optimal performance [18]. Secondly, and touching on many of the issues identified in the first, compression bras largely lack adjustability, which means when the elastane content quality begins to deteriorate over the course of use, the degree of support provided will be subsequently affected. Alternatively, with a typical encapsulation bra, there may be a zip or hook & eye closure which allows for a far less compromised and stable underband – with the latter fastening option also enabling a tighter underband fit once the fit starts to falter.

As is also common with standard bras, the use of these multiple row and column hook & eyes closures (such as the common three by three) in sports bras can compensate for the reduction in elasticity that will inevitably occur over the item’s use. With users ideally fitting and initially wearing their bra on the loosest hook adjuster – as the elastane will provide sufficient support when new – tighter hooks can be used to adjust the loosening fit and maintain optimal support. As stated, compression bras often lack such a feature, which means there is no capacity to compensate for the bra’s gradual stretch, which will be especially detrimental for larger cup volumes which will require more intense elastication to sufficiently support the breasts [1].

Additionally, as previously discussed, the stretch employed to enable donning, doffing and indeed, to compress and secure the breasts against the chest wall, also appears detrimental to the support afforded by the garment while exercising – especially in the more difficult to contain and control larger breast volumes. This has led to a number of academic papers published on the effectiveness of different style bras, and indeed the expertise of bra fit and design experts, identifying that compression bras – which lack a defined cup structure – are perfectly capable of providing adequate support for smaller bust sizes. However, overall they are the least-effective model of sports bras, due in part to their less proficient support of larger bust volumes. While there are suggestions that the exact sizing bracket for the compression style sits within cup sizes AA-C, due to the nature of sister sizing – whereby a 38A has the same cup volume as a 36B, 34C, 32D, 30DD and 28E – this recommendation is suited as guidance rather than rule [14], [21]. Instead, fitting and personal preference will determine whether a compression styled bra will adequately support the bust for a specific individual.

Regardless of this assessment of compression styles from experts in the field, studies assessing the adoption rate of sports bras by women have highlighted that sturdier encapsulation bras and combination styles suitable for a wider range of breast volumes appear less commonly worn, with use rates of 14.8% and 26.7%, respectively [1]. In another study, despite participants being familiar with the premise of encapsulation bras (71% of survey participants are aware of such sports bras), only 41% of respondents wore such a bra during exercise [21]. As discussed, this can be detrimental to user comfort and breast support as it suggests that the ultimately less supportive compression bras are being utilised instead, with an adaptation rate comparable to the encapsulation and combination styles of 48.2% [1]. Another source, analysing the usage of sports bras by female marathon runners, found a similar trend of usage across the type categories, with 43% of participants reporting the use of compression styles, 29% choosing encapsulation and 24% opting for a combination bra [6]. Despite these challenges facing the consumer adoption of both encapsulation and combination sports bras, the styles appear to be currently worn far more often by older demographics and women of a larger bust size, likely corresponding with an increased demand on breast movement control [6].

Encapsulation and combination bras are deemed more supportive due to their use of structural cups. Encapsulation bras specifically utilise an aesthetic form much more comparable with traditional bra design, featuring familiar pattern components such as three-dimensional cups, a stabilising centre front gore panel and usually adjustable straps which enable a greater degree of personalised fit. How combination styles differ from encapsulation is the use of compressive elements, usually a stretch outer which provides smooth shaping over the bust. “Normally on the face of it, the bra looks quite a lot like a compression type bra,” says Horler. “You’ve got a layer of compressive fabric over the front, however, inside you’ll see there’s that separation, like you’d see with the encapsulation sports bra.” As combinations are a hybrid approach to sports bra design, featuring elements of both compression and encapsulation, Horler notes that the precise design is ‘more along a continuum’, in that some may heavily focus on an encapsulation effect, with simply a compressive outer layer, while others may feature some light seaming to provide a dimensional cup and instead will rely heavily on the garment’s tension on the body in the provision of support.

4. Introduction to Part II: Strong commercial examples and academic analysis of design

With the fundamentals, challenges and opportunities affiliated with sports bras established, the concluding part to this report series will involve an analysis of current commercial bra styles which have achieved industry recognition for their design and performance. This examination will include a comprehensive construction breakdown, utilising illustrative technical drawings, to explore the features that assist in delivering high levels of support.

Additionally, a number of contemporary studies relating to the optimal design and development of sports bras will be examined, including a study on the consumer product preferences of differing cultural and regional populations. Other academic directions observed within the report include a proposal for generative sports bra design via body scan processing and the study and statistical allocation of breast movement reduction performance to individual design variables.