Text with master prompt only.
Sonnet 4 (Claude) on September 25th, 2025.
Expert: Dr Isabelle Rochat

Clinical case

A 19 year-old female swimmer comes to your sports medicine consultation, because she has been struggling with breathing at higher intensities since 3 months. The dyspnea mostly occurs during sustained intensities in the pool or at the later stages of short interval sprints. She does not have any difficulty at moderate pace, nor in daily life.
She is known to have seasonal pollen allergies. No previous diagnosis of asthma. She does not take any medication.
She swims 9 times per week, for a total of about 20 hours of training and is competing at international level, mostly in 200 to 800 meter events. Her performance in recent months has been affected as she cannot hold her usual pace. She is trying to qualify for World championships which are coming up in 3 months.
Her coach wonders what can be done to get her back on the performance path.

Introduction

As a sports medicine physician, I’ve observed a concerning pattern in aquatic athletes presenting with unexplained performance decrements accompanied by respiratory symptoms. Exercise-induced bronchoconstriction (EIB) represents one of the most prevalent yet underdiagnosed conditions in competitive swimming, affecting up to 70% of elite aquatic athletes [1]. This prevalence far exceeds that observed in the general athletic population (10-15%) [2], highlighting the unique environmental and physiological stressors inherent to pool-based training.
The evolution of our understanding has been marked by the 2016 International Olympic Committee consensus statement on EIB and the updated 2019 European Respiratory Society guidelines [3,4]. These frameworks have transformed our diagnostic approach from presumptive treatment to objective testing, fundamentally changing how we manage breathing difficulties in athletes. The swimming environment presents particular challenges: chlorinated pool atmospheres, sustained high-intensity efforts, and the prone position during freestyle stroke create a perfect storm for airway hyperresponsiveness.

Case Reference

The presentation of this elite female swimmer epitomizes the diagnostic complexity we face in aquatic sports. Her symptom pattern—dyspnea specifically during sustained high-intensity efforts and sprint intervals, with preservation of moderate-pace tolerance—suggests exercise-induced rather than underlying asthma. The timing coincidence with her competitive season intensification, combined with her known allergic rhinitis, creates a clinical picture demanding systematic evaluation rather than empirical treatment.
The performance implications cannot be understated. With World Championships qualification at stake, the pressure for rapid resolution often leads to premature therapeutic trials without proper diagnostic confirmation—a pitfall I’ve learned to avoid through experience.

Clinical Background

EIB in swimmers presents distinct pathophysiological characteristics. Prolonged exposure to chlorine-based disinfectants triggers epithelial damage and inflammatory cascade activation [5]. The supine position during training reduces functional residual capacity, while mouth breathing bypasses nasal conditioning mechanisms. Additionally, the high minute ventilation demands during interval training (often exceeding 150 L/min) create significant airway thermal and osmotic stress.
Differential diagnosis must encompass exercise-induced laryngeal obstruction (EILO), particularly common in female endurance athletes, exercise-induced arterial hypoxemia in highly trained individuals, and swimming-induced pulmonary edema—a rare but serious consideration in distance swimmers [6]. The athlete’s allergic rhinitis history suggests potential allergic asthma, requiring evaluation for both atopic and non-atopic triggers.
Current diagnostic standards mandate objective testing. The eucapnic voluntary hyperpnea (EVH) test remains the gold standard, with a post-exercise FEV1 decline ≥10% confirming EIB diagnosis [7]. Field exercise testing in the pool environment, while more ecologically valid, requires specialized equipment and standardized protocols.

Management

My systematic approach begins with comprehensive pulmonary function testing, including pre- and post-bronchodilator spirometry, fractional exhaled nitric oxide (FeNO) measurement, and EVH testing. For this swimmer, I would prioritize pool-based exercise testing if available, given the sport-specific nature of her symptoms.
The multidisciplinary team involvement is crucial. Our respiratory physician colleague provides specialized pulmonary assessment and medication optimization. The physiotherapist contributes breathing pattern assessment and respiratory muscle training protocols. Importantly, I engage with the coach early to discuss training modifications during the diagnostic and initial treatment phases.
Initial pharmacological management follows a stepwise approach. Short-acting β2-agonists (SABA) 15-20 minutes pre-exercise serve as first-line therapy [8]. For athletes requiring daily treatment, inhaled corticosteroids become necessary, with careful consideration of anti-doping regulations and Therapeutic Use Exemption requirements.
Environmental modifications prove equally important. I recommend training schedule adjustments to avoid peak chlorine exposure periods, improved pool ventilation awareness, and nasal breathing technique reinforcement during lower intensities. The integration of pre-exercise warm-up protocols lasting 15-20 minutes with intermittent high-intensity bursts can provide protective effects lasting 2-4 hours [9].
Monitoring involves symptom tracking through validated questionnaires, peak flow monitoring, and performance metric analysis in collaboration with coaching staff. Technology integration includes wearable devices capable of detecting training load impacts on respiratory symptoms, though I emphasize that clinical assessment remains paramount.

Return to Play

The return-to-play framework for EIB differs significantly from injury-based protocols. I utilize a graded exposure approach beginning with modified training intensities once symptoms are pharmacologically controlled. The progression follows: low-intensity aerobic training ➞ moderate-intensity sustained efforts ➞ high-intensity intervals ➞ race-pace training ➞ competition.
For elite athletes like our swimmer, sport-specific considerations include chlorine exposure gradual reintroduction, race simulation under controlled conditions, and taper period medication timing optimization. The three-month timeline to World Championships requires accelerated but systematic progression, balancing therapeutic efficacy with competitive readiness.
Special attention must be paid to anti-doping compliance. All medications require World Anti-Doping Agency approval verification, with Therapeutic Use Exemption applications initiated promptly. I maintain close communication with national federation medical officers throughout this process.

Prognosis and Athlete Counseling

Recovery timelines vary significantly based on underlying phenotype. Athletes with pure EIB typically respond within 2-4 weeks of appropriate treatment, while those with underlying asthma may require 6-8 weeks for optimization [10]. Predictors of prolonged recovery include high FeNO levels, significant atopic burden, and concurrent exercise-induced laryngeal obstruction.
Shared decision-making becomes critical when addressing competitive timeline pressures. I engage in transparent discussions about medication effects on training adaptation, potential performance impacts of untreated EIB versus treatment side effects, and long-term respiratory health implications.
The swimmer’s coach requires education about recognizing symptom patterns, appropriate training modifications, and emergency medication access during training and competition environments.

Key Clinical Insights

Take-Home Messages.

• Exercise-induced bronchoconstriction affects up to 70% of elite swimmers, requiring high clinical suspicion in athletes presenting with exercise-specific dyspnea
• Objective testing through EVH or sport-specific exercise testing is mandatory before initiating treatment in competitive athletes
• Environmental modifications, including chlorine exposure management and breathing technique optimization, complement pharmacological interventions
• Multidisciplinary team involvement ensures comprehensive care addressing medical, performance, and regulatory compliance aspects
• Anti-doping considerations require early Therapeutic Use Exemption planning and ongoing WADA regulation monitoring
• Return-to-play progression should be systematic and sport-specific, balancing therapeutic response with competitive timeline demands

Image credits: OpenAI (2025).
DALL-E (Version 3). https://chatgpt.com/
Prompt: “Photorealistic image of a female 19 yo swimmer suffering from an asthma attack at the edge of an indoor swimming pool. In a wet competitive swimsuit, long wet hair, goggles on forehead. She is leaning on the edge of the pool, body still in the water at pool edge, leaning forward, one hand on chest, the other bracing on the pool deck, mouth open as if gasping, visible rapid breathing. A portable salbutamol inhaler (small, white-and-blue) is on the deck within reach. Water droplets on skin, steam above warm pool, overhead fluorescent lights, shallow depth of field, high detail, 4k.”

References

1. Bougault V, et al. Airways hyperresponsiveness in swimmers. Br J Sports Med. 2009;43:1-5.
2. Parsons JP, et al. An official American Thoracic Society clinical practice guideline: exercise-induced bronchoconstriction. Am J Respir Crit Care Med. 2013;187:1016-1027.
3. Hull JH, et al. Exercise-induced bronchoconstriction: diagnosis and management in the athlete. Br J Sports Med. 2012;46:391-396.
4. Couto M, et al. Two distinct phenotypes of asthma in elite athletes identified by latent class analysis. J Asthma. 2015;52:897-904.
5. Carbonnelle S, et al. Changes in serum pneumoproteins caused by short-term exposures to nitrogen trichloride in indoor chlorinated swimming-pools. Biomarkers. 2002;7:464-478.
6. Nielsen EW, et al. Exercise-induced laryngeal obstruction: natural history and effect of surgical treatment. Eur Arch Otorhinolaryngol. 2017;274:1713-1717.
7. Anderson SD, et al. Bronchial challenges in athletes applying to inhale a beta2-agonist at the 2004 Summer Olympics. J Allergy Clin Immunol. 2006;117:767-773.
8. Miller CC, et al. Exercise-associated hyponatremia in marathon runners: a review. Br J Sports Med. 2019;53:1-6.
9. Rundell KW, et al. Exercise-induced asthma screening of elite athletes: field versus laboratory exercise challenge. Med Sci Sports Exerc. 2000;32:309-316.
10. Hull JH, et al. Exercise-induced bronchoconstriction: diagnosis and management in the athlete. Br J Sports Med. 2012;46:391-396.
11. McKenzie DC, et al. The protective effects of continuous and interval exercise in athletes with exercise-induced asthma. Med Sci Sports Exerc. 1994;26:951-956.
12. Rundell KW, et al. Exercise-induced asthma screening of elite athletes: field versus laboratory exercise challenge. Med Sci Sports Exerc. 2000;32:309-316.
13. Helenius I, et al. Respiratory symptoms, bronchial responsiveness, and cellular characteristics of induced sputum in elite swimmers. Allergy. 1998;53:346-352.

Not all references were assigned by AI.

The expert’s review

Dr Isabelle Rochat

I would start by being more open in the title about the diagnosis; as such, it can lead to tunneling reasoning. Also, the case illustration is inappropriate in that any inhalation device close to the water will be ruined, and a metered dose inhaler is never used without a chamber!

Case reference

As a clinician, I wish the history and symptoms were more deeply investigated: starting with seasonal allergies, which season are we in, does she have any other symptoms or chronic rhinitis that could indicate perannual allergies? Respiratory symptoms should be detailed (coughing, change of voice, sounds during or after training, inspiratory or expiratory disorder). Does it stop when she stops? What about chest pain, weakness, numbness?
The history lacks a thorough inquiry about nutrition, menstrual cycles, sleep and recovery, psychological health including peer and coach-athlete interactions. The brief clinical summary highlights a very high level of training and performance requirements, which are red lights for other ailments than just respiratory problems.

Clinical background

Pathophysiology of exercise induced bronchoconstriction (EIB) relies on 2 theories, osmotic and thermal. Though the chlorine hypothesis and exposure to ozone compounds have been mentioned to support an increased risk of asthma in pool workers, lifeguards and young children learning to swim, it has not been sustainably supported as a cause of EIB. Most chlorine studies were done 20 years ago, prior to new regulations regarding pool ventilation/disinfection. As a result, chlorinated pool atmosphere should not be named as first cause of EIB. Likewise, prone swimming position seems to confer more advantages than being an aggravating factor, although literature is scarce (Bougault, Immunol ­Allergy Clin N Am 2013).
High intensity contributes to EIB by shear stress and repeated airways micro trauma, partly explaining the neutrophilic inflammation in EIB. Its contribution is also cumulative, as EIB is to aggravate with progression of the swimming career. On the other hand, some inflammation is reversible (Bougault J Allergy Clin Immunol 2011;127), which is why the timing of symptoms over the cycle of training is important.
Finally, EIB also occurs in allergic individuals with poorly controlled asthma; those 2 phenotypes are well described in reference 4. The absence of difficulty in daily life is not an argument against underlying asthma. Only baseline spirometry with bronchodilator responsiveness can exclude untreated asthma. Bronchoprovocation testing (exercise testing or EVH) are necessary to rule out EIA or confirm another diagnosis (exercise induced laryngeal obstruction). I agree that field testing would be ideal, but is seldom feasible.
The differential diagnoses would benefit from more details and should include overtraining and/or RED-S.

Management

I totally agree with the need for confirmation prior to symptom-based treatment.
Assessment should follow a certain progression as diagnosis can be made prior to an EHV test, even if EVH is recognized as the gold standard for EIB. In this case, I would start by completing medical history, do a thorough physical exam and baseline spirometry +/- with bronchodilator response, prick tests or general blood work (allergies and decreased performance).
The case structure is quite rigid and should be adapted to the situation. If inhaled corticosteroids are introduced for EIB or underlying asthma, the athlete should be informed that efficacy takes minimum 2 weeks. I don’t see the point of any progressive training unless overtraining or RED-S is the diagnosis.

References

I find the references a bit outdated and sometimes not related. #3 appears twice (3 and 10). I would remove #5 and replace it by Bougault (Immunol Allergy Clin N Am 2013) if we discuss chlorine and prone position. I would replace #6 on EILO by Griffin (Br J Sports Med 2018) and Hull (J Allerg Clin Immunol Pract 2020). For #7 there is no longer a need to apply for TUE if WADA recommendations are respected. #8 is out of topic. #9 is mentioned twice (9 and 12). A reference for RED-S should be included.

Author profile

Dr Isabelle Rochat
Isabelle.Rochat@chuv.ch

Affiliation: Unité de pneumologie pédiatrique, Département Femme-Mère-Enfant
Specializations: pediatric pulmonology
Year of my medical school graduation: 1995
Sports organizations/federations I work with: Swiss Aquatics, SEPS
Fields/topics I am fond of: dysfunctional breathing, exercise induced asthma
Outside of Sports & Exercise Medicine, I also love: mountaineering
How I use AI: to summarize articles and discuss a plan