Sports bras for girls: when the first one is needed, and how to get the size right

A first sports bra is needed as soon as breast development begins — there is no set age: the cue is the body, not the calendar. At 13-14, one girl in two says her breasts affect her participation in sport, yet only one in ten always wears one — and the girls who never wear one are more often those with smaller breasts. How to spot a wrong size, when compression beats encapsulation, how often to recheck the fit while growing, and why an education booklet in a randomised trial got 39% more athletes through a bra-fit test.

At puberty the body changes fast, and a growing chest is one of the changes almost nobody talks about in sport. Yet it's very real, and it's measurable: at 13-14, one girl in two says her breasts affect her participation in sport — while only one in ten always wears a sports bra. A good sports bra isn't a detail: it's what lets a girl keep playing while feeling comfortable in her own body.

In short

  • 46% of girls aged 11-18 say their breasts affect participation in compulsory sport: 51% at 13-14, 63% with larger cup sizes (Scurr et al., 2016).
  • 73% have at least one breast-specific concern in sport; the most common is bounce (38%).
  • Only 10% always wear a sports bra; over half never do.
  • 87% want to know more — and 50 minutes of education is enough to change the habits of two-thirds of girls (Omrani et al., 2020).

Why does a sports bra matter more than it seems?

Breast tissue has no muscle holding it in place: internal support is weak, so during running and jumping it moves independently of the rest of the body, and the more so the larger the breast (Scurr et al., 2016). In adult women with a D cup, unsupported breast displacement goes from about 4.2 cm when walking to 15.2 cm when running (Scurr et al., 2011).

One necessary caveat: those centimetres are measured on adult women, not adolescents. No equivalent biomechanical data exists for 13- and 14-year-olds, and extrapolating would be wrong. The figure that speaks directly about them is different — self-reported, but large. Among 2,089 British girls aged 11-18, 46% reported their breasts had some effect on their participation in compulsory sport — 51% at exactly 13-14, 63% among those with larger cup sizes. 73% reported at least one breast-specific concern in sport: the most common was bounce (38%), followed by embarrassment when changing (34%) (Scurr et al., 2016).

Without proper support there's discomfort, and there's — just as important — self-consciousness: the fear of being watched leads many girls to cover up, avoid certain exercises, hang back. The silence around this topic doesn't protect anyone: it pushes girls away, exactly as it does with the menstrual cycle.

The good news is that among the reasons a girl leaves sport, this is by far the easiest one to take off the table.

At what age is a first sports bra needed?

There's no "right" age: the cue is the body, not the calendar. A sports bra is needed as soon as breast development begins, or the moment there's any discomfort when moving. It's not about size or how much you've "developed" — it's about comfort and confidence. Better early than waiting until discomfort becomes a reason to skip training.

The data says girls get there late, and for the wrong reason. In Scurr and colleagues' study, over half of the girls never wore a sports bra and only 10% always did — against 78% of active adult women and 91% of marathon runners. And the girls most likely never to wear one had smaller breasts (49%) rather than larger ones (35%): a sign that it's read as a question of size, when it's a question of movement.

How do you know if the size is right?

A sports bra works on two measurements: the band (snug but not tight) and the cup (it should contain without compressing or spilling over). Signs the size is wrong:

Through the growing years the body changes often, so it's normal to recheck the size every 6–12 months and replace the bra when the elastic loosens and no longer supports. This is not a maintenance detail: breast development happens in the same window as the growth spurt, whose estimated mean age in young female athletes is 11.18 years, with a 90% credible interval from 8.62 to 12.94 years (Lima et al., 2024). A size that fits in September may not fit by March.

And education here is not generic advice: it is a tested intervention. In a cluster-randomised trial of 115 adolescent athletes from four regional sporting academies (mean age 16), the group given an education booklet on bra fit and breast support by a sports physiotherapist had, at four months, improved their bra knowledge by 19% more than controls (95% CI 14-25), and 39% more of them passed the Bra Fit Assessment (95% CI 19-54) and 30% more the Level of Breast Support test (95% CI 11-47). The authors are explicit on one point: baseline knowledge, fit and support were all poor (McGhee et al., 2010). One honest caveat: in the same trial, breast discomfort during exercise did not change significantly — the booklet improves what gets worn, not the symptom on its own.

Compression or encapsulation — which is better?

These are the two main types:

Many modern designs combine the two. The rule of thumb: the higher the impact of the sport, the more support you need.

What can coaches and parents do?

Is talking about it enough to change habits?

It's rare to be able to say this so plainly. In a study of 787 girls aged 11-14, 87% reported at least one breast-specific concern and one in four had negative feelings about their breasts. After a single 50-minute education session, two-thirds started wearing a sports bra and half changed size (Omrani et al., 2020). In Scurr's study, 87% of girls wanted to know more about their breasts, and 44% specifically about breasts and sports bras.

The demand is there. It's the supply that's missing — and it's free.

A changing chest should never be a reason to leave sport. With the right information and an environment that talks about it without judgement, it stays what it is: a piece of equipment. Which is, in the end, the point of a coach's words: naming something matter-of-factly is already half the work.

BAB helps adolescent athletes get to know and listen to their changing bodies, and gives parents and clubs the tools to support them the right way. So that no girl stops playing because she feels out of place.

Sources

This article is for information only and does not constitute medical advice. If breast pain persists, speak to a healthcare professional.

At what age is a first sports bra needed?

There's no «right» age: the cue is the body, not the calendar. One is needed as soon as breast development begins, or the moment there's any discomfort when moving. The data suggests girls get there late: in a study of 2,089 British girls aged 11-18, over half never wore a sports bra and only 10% always wore one during sport and exercise (Scurr et al., 2016). Strikingly, girls with smaller breasts were more likely never to wear one (49%) than girls with larger breasts (35%) — a sign that it's perceived as a question of size, when it's a question of comfort.

Can breasts really make a girl stop playing sport?

They can reduce her participation, and it's documented. Among 2,089 girls aged 11-18, 46% reported their breasts had some effect on their participation in compulsory sport: rising to 51% at ages 13-14 and 63% among girls with larger cup sizes. 73% reported at least one breast-specific concern in sport, the most common being breast bounce (38%) (Scurr et al., 2016). To be honest about it: this is a cross-sectional, self-reported association of modest effect size — not proof that breasts «make girls quit». But it's a real source of friction, and unlike most others it can simply be removed.

How do you know if the size is wrong?

Three practical signs: the band rides up the back during movement (too loose), the straps dig in or hurt (too tight, or carrying all the weight), the breast spills over the edges (cup too small). Through the growing years it's normal to recheck the size every 6-12 months. And education works: after a single 50-minute session with 787 girls aged 11-14, two-thirds started wearing a sports bra and half changed size (Omrani et al., 2020).

Is a sports bra needed even with small breasts?

Yes — and this is the most common misconception. In the study of 2,089 British girls aged 11-18, girls with smaller breasts were more likely never to wear one (49%) than girls with larger breasts (35%) (Scurr et al., 2016). Breast tissue has no muscle of its own to support it: what matters isn't cup size but how much the breast moves during running and jumping, and the discomfort is felt at any size. The practical rule: the higher the impact of the sport, the more support is needed.

How often should a sports bra size be rechecked while growing?

Every 6-12 months while the body is changing, and any time one of the three wrong-size signs appears: the band riding up, straps digging in, the breast spilling over the edges. The reason is that the size moves with everything else: breast development happens in the same window as the growth spurt, whose estimated mean age in young female athletes is 11.18 years with a 90% credible interval from 8.62 to 12.94 years (Lima et al., 2024). A size that fits in September says nothing about March. And checking works: in a cluster-randomised trial of 115 adolescent athletes, 39% more of those given an education booklet passed the bra-fit test than controls (McGhee et al., 2010).

Compression or encapsulation — which is better?

It depends on the impact of the sport and the stage of development. Compression gently flattens the breast towards the body: simple, comfortable, and well suited to first bras and low-to-medium impact activity. Encapsulation has two separate cups supporting each breast individually and gives more support: better for running, jumping and team sports, or for larger cup sizes. Many models combine both. Neither is «more correct»: choose on impact and comfort, and recheck the size every 6-12 months through the growing years.