‘Runner’s Waist’, ‘Cortisol Face’ and the Fight for Young Women’s Sport

Exercise myths collide with high-performance reality

A spate of new social media exercise trends has raised concerns that young Kiwi women are being discouraged from healthy training at the very moment women’s sport is enjoying unprecedented global visibility.

Buzzwords such as “runner’s waist” and “cortisol face” have been singled out by non-profit ExerciseNZ as trends that leverage fears of appearing bulky or puffy to push young women away from running, strength work and gym-based conditioning.

Both non-scientifically backed ideas claim that regular exercise creates boxy, wider or swollen-looking bodies. For teenage girls and young women moving through school sport, club systems and high‑performance pathways, that message cuts directly against what coaches and federations are trying to build: resilient athletes with strong, durable bodies.

Decades of progress under threat

ExerciseNZ chief executive Richard Beddie said the trends were especially disappointing, given it had taken decades to cultivate a healthier public perspective on exercise and training.

“Health and mental wellbeing are consistently the two most common reasons people exercise. But these latest social media crazes buck that trend, often driven by online influencers with little or no formal training in exercise, health or wellbeing,” he said.

The organisation said the trends circulating on social platforms had no scientific evidence behind them. For sports systems that depend on long‑term athlete development, that lack of evidence has real‑world consequences: if even a small proportion of young women reduce their training load to protect a particular “look”, it can affect talent depth, retention and performance standards across codes.

The ‘runner’s waist’ myth and endurance sport

The “runner’s waist” myth claims that regular running will create a wider, boxier waist due to more visible oblique muscles. Beddie pointed to research in a medically reviewed article by Healthline which found that while running activates the core, it does not provide the heavy resistance needed to significantly increase the size of the obliques.

Instead, consistent running develops:

• endurance and cardiovascular health
• core stability and balance
• overall fitness needed for both recreational and competitive sport

The article concluded that “the idea that running makes your waist bigger is misleading and potentially dangerous”. It noted that primary research shows running activates the core for stability and endurance, but at intensities far below what is required to increase muscle size, “making the idea that it ‘widens your waist’ physiologically implausible”.

For athletes in sports governed by bodies such as World Athletics, sustained running volume underpins everything from age‑group cross‑country to elite marathon and middle‑distance programmes. If myths like “runner’s waist” cause young women to opt out of higher-mileage phases, performance ceilings in those events will inevitably be lower and national systems will struggle to keep pace with global standards.

‘Cortisol face’ and the fear of looking stressed

“Cortisol face” is another trend circulating on TikTok and Instagram, suggesting exercise will cause facial puffiness and bloating through elevated stress hormones and cortisol levels. The narrative is simple: train hard, and your face will show it in all the wrong ways.

Medical experts from the Ohio State Wexner Medical Centre have said this is not a recognised medical condition. Beddie stressed the gap between viral claims and clinical reality.

“While rare disorders that cause abnormally high cortisol levels can change facial appearance, everyday exercise and normal life stress do not create the dramatic facial changes portrayed across TikTok and Instagram,” he explained.

For competitive athletes, especially those on televised or streamed stages, appearance‑based myths can heighten an already intense scrutiny. If young women start to associate hard training blocks, tournament travel or pressure environments with exaggerated “cortisol face” imagery, there is a risk they may dial back effort at precisely the point when conditioning and resilience are most needed.

Strength training, ‘bulk’ myths and modern performance

Becoming “bulky” through weightlifting was another persistent misconception highlighted by Beddie. He said substantial muscle mass required “years of progressive resistance training, carefully managed nutrition and, in many cases, favourable genetics”.

That picture aligns with how strength and conditioning is structured across high‑performance sport:

• progressive overload over multiple seasons
• individualised programmes based on position, event or discipline
• nutrition tailored to performance, recovery and health, not quick cosmetic change

In women’s rugby, football, basketball, netball and combat sports, strength training is now considered non‑negotiable for injury prevention, acceleration, stability in contact and late‑game endurance. Myths that a handful of gym sessions will instantly produce unwanted bulk risk deterring young players from the very work that keeps them on the field or court.

Body image, selection pressure and the social media lens

Beddie said he felt the greatest concern was not the specific buzzwords, but what they revealed about how young women viewed themselves.

“We’ve gone from celebrating what our bodies can do to worrying about whether our waistline or face fits the latest TikTok trend. That’s a step backwards,” he said.

In elite environments, selection is driven by performance, availability and tactical fit. Yet the social media lens can shift attention from metrics such as distance covered, repeat sprint ability or strength benchmarks to angles, filters and exaggerated before‑and‑after imagery. For school and club athletes trying to win selection, the fear of standing out physically – of appearing too strong, too muscular, too different from trending aesthetics – can make them less likely to embrace the conditioning that coaches and medical staff recommend.

Beddie added that it was ironic that the very activities that improve people’s health – regular exercise, running and strength training – were being targeted by these trends.

Public health and participation at stake

While the discussion has largely played out on social platforms, the stakes extend far beyond individual fitness goals. For national sporting bodies and public health agencies, participation in physical activity underpins everything from long‑term athlete development to reduced healthcare costs and community wellbeing.

If myths like “runner’s waist” and “cortisol face” discourage girls and young women from joining school teams, local clubs or community running groups, the impact is felt in:

• shallower talent pools for federations and leagues
• higher drop‑out rates during the critical teenage years
• fewer role models progressing into elite or professional environments

Those trends can, over time, alter the competitive balance of international sport, as countries that successfully protect girls’ participation and confidence will have structural advantages over those that do not.

Choosing credible advice in a high‑noise era

Beddie urged young women to be cautious when taking health and training advice from social media personalities.

“Exercise should never be about chasing the latest social media ideal. It should be about improving your health, building confidence, feeling strong and giving yourself the best chance of living a long, healthy life. That’s something no viral trend should ever take away,” he said.

“Your body isn’t a trend.”