Links To And Excerpts From Orthostatic intolerance as a potential contributor to prolonged fatigue and inconsistent performance in elite swimmers

For the treatment of orthostatic intolerance and postural orthostatic tachycardia syndrome, please see Therapy For Orthostatic Intolerance From The Johns Hopkins Chronic Fatigue Clinic. Posted on August 14, 2022 by Tom Wade MD

In this post, I link to and excerpt from Orthostatic intolerance as a potential contributor to prolonged fatigue and inconsistent performance in elite swimmers [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. BMC Sports Sci Med Rehabil. 2022; 14: 139.Published online 2022 Jul 23. doi: 10.1186/s13102-022-00529-8A

There were twelve similar articles in PubMed Central.

All that follows is from the above resource.



Athletic underperformance is characterized by fatigue and an inability to sustain a consistent exercise workload. We describe five elite swimmers with prolonged fatigue and athletic underperformance. Based on our work in myalgic encephalomyelitis /chronic fatigue syndrome, we focused on orthostatic intolerance as a possible contributor to symptoms.


Participants were referred for evaluation of fatigue and underperformance to the Chronic Fatigue Clinic at the Johns Hopkins Children’s Center. All patients were evaluated for overtraining syndrome, as well as for features commonly seen in myalgic encephalomyelitis/chronic fatigue syndrome. The latter included joint hypermobility, orthostatic intolerance, and non-IgE mediated milk protein intolerance. Orthostatic intolerance was tested by performing a ten-minute passive standing test or a head-up tilt table test.


Orthostatic testing provoked fatigue and other symptoms in all five swimmers, two of whom met heart rate criteria for postural tachycardia syndrome. Treatment was individualized, primarily consisting of an increased intake of sodium chloride and fluids to address orthostasis. All patients experienced a relatively prompt improvement in fatigue and other orthostatic symptoms and were able to either return to their expected level of performance or improve their practice consistency.


Orthostatic intolerance was an easily measured and treatable contributor to athletic underperformance in the five elite swimmers we describe. We suggest that passive standing tests or formal tilt table tests be incorporated into the clinical evaluation of athletes with fatigue and underperformance as well as into scientific studies of this topic. Recognition and treatment of orthostatic intolerance provides a new avenue for improving outcomes in underperforming athletes.

Keywords: Athletic underperformance, Overtraining, Postural tachycardia syndrome, Orthostatic intolerance, Post-exertional malaise, Chronic fatigue syndrome, Neurally mediated hypotension


Athletic underperformance, sometimes referred to as overtraining syndrome, is characterized by fatigue and the inability to sustain a consistent exercise workload as compared to a given individual’s baseline performance []. While nutritional factors, hormonal imbalance, and autonomic abnormalities have been proposed as contributors to this phenomenon [], no consistent biomarker for athletic underperformance or overtraining has been identified. Available treatments have primarily focused on stress reduction, optimization of nutrition, and adequate rest.

Orthostatic intolerance is a clinical disorder in which symptoms such as lightheadedness, fatigue, headaches, nausea, and cognitive difficulties are provoked by upright posture and ameliorated by recumbency []. These symptoms are thought to be due to a combination of suboptimal cerebral blood flow and an exaggerated sympatho-adrenal response when upright []. Common forms of orthostatic intolerance in adolescents and young adults include disorders with measurable heart rate and blood pressure abnormalities, such as postural tachycardia syndrome (POTS) [], in which elevations in norepinephrine are prominent during upright posture, and neurally mediated hypotension [], which often is associated with a rise in epinephrine during orthostatic stress. These conditions are not mutually exclusive and can occur in the same person. Individuals with orthostatic symptoms also can have a substantial reduction in cerebral blood flow despite a normal heart rate and blood pressure response to upright posture [], and are characterized as having low orthostatic tolerance. In this group, the number of orthostatic symptoms correlates with the reductions in cerebral blood flow.

We describe a case series of five elite swimmers evaluated for chronic fatigue and decreased athletic performance. All five were unable to replicate their usual practice speed and workload from day to day. Based on discoveries about the importance of orthostatic intolerance to the pathophysiology of fatigue and post-exertional malaise (PEM) in individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) [], we had a higher index of suspicion for orthostatic intolerance as a treatable contributor to their abnormal fatigue and prolonged, inconsistent performance.


All [five] individuals underwent a careful history and laboratory work-up for common causes of chronic fatigue by a physician with experience in the evaluation of ME/CFS and orthostatic intolerance (PCR). This included a complete blood count with differential white blood cell count, a comprehensive metabolic panel (electrolytes, creatinine, urea, total protein, albumin, calcium, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total bilirubin), free T4, thyroid stimulating hormone, c-reactive protein or erythrocyte sedimentation rate, vitamin B12, measures of iron stores, and a urinalysis. Other tests were obtained selectively based on the initial results of the basic testing panel.

There is a well-recognized association between joint hypermobility and chronic fatigue, and between joint hypermobility and orthostatic intolerance [19–27]. As a result, we routinely assess joint hypermobility in our evaluation of individuals with fatigue. The physical examination therefore included the nine-point Beighton score*, a commonly used and reliable measure of joint hypermobility [28]. Joint hypermobility was considered present if the Beighton score was four or higher.

*ASSESSING JOINT HYPERMOBILITY-THE BEIGHTON SCORING SYSTEM from The Ehlers-Danlos Society (accessed 8-13-2022).

There is a strong association between orthostatic intolerance and chronic fatigue [13, 14, 17, 18]. As such, all individuals presenting to our clinic with prolonged fatigue also are evaluated routinely for orthostatic intolerance. Three of the five had a ten-minute passive standing test in the clinic [29]. For the standing tests, we recorded heart rate and blood pressure at one-minute intervals (a) while the patient was supine for five minutes, (b) while the patient was standing upright and motionless for 10 min, and (c) while supine at the end of the standing phase for two minutes. While standing, the patient’s heels were 2 to 6 inches from the base of the wall, with the upper back against the wall. A fourth patient evaluated by telemedicine was instructed to conduct the same test assisted by a colleague at home using a wristband heart rate monitor; blood pressure measurements were not obtained. One individual had a head-up tilt table test prior to referral. During the passive standing tests, we instructed patients to minimize movements. We ascertained symptom severity at the completion of the supine phase, at one-to-two-minute intervals while standing, and during the post-test supine phase. Individuals reported symptoms on a 0–10 scale, with 0 meaning absence of the symptom and 10 being the worst severity imaginable. For individuals 12–19 years, the diagnosis of POTS required at least a 40 beat per minute (bpm) increase in heart rate between the lowest supine value and the peak while standing; a 30 bpm increase was required for those 20 and older [7]. The diagnosis of orthostatic intolerance was made if individuals had provocation of their presenting symptoms during the standing test, regardless of whether they also met criteria for POTS. Healthy individuals usually tolerate the 10-min standing test or tilt test without developing symptoms.

Based on prior observations in our clinic that 31% of patients with ME/CFS have evidence of a non-IgE mediated milk protein intolerance*, we ascertained for the common upper gastrointestinal symptoms associated with milk protein intolerance, namely epigastric pain, early satiety, and gastroesophageal reflux, often associated with recurrent aphthous ulcers [30]. In those with symptoms suspicious for milk protein intolerance, a trial of eliminating milk protein from the diet was conducted immediately after clinical evaluation to ensure that continued exposure to milk protein was not interfering with assessing the response to other interventions.

*Protein Intolerance from StatPearls (accessed 8-13-2022)

The five detailed discussions of the individual athletes’ testing should be reviewed in pp 3 – 7 of the PDFof the article.


This case series draws attention to the potential for orthostatic intolerance to be an important contributor to the pathophysiology of inconsistent performance in elite swimmers. All five athletes reported fatigue as a consistent symptom, often worse in positions of upright posture or in hot environments, usually associated with lightheadedness. Testing that involved brief periods of upright posture provoked their typical symptoms, sometimes associated with orthostatic tachycardia. Individualized treatment directed at the orthostatic intolerance and other symptoms was associated with improvement, and in most cases resolution, of the inconsistency in training and competition performance. Larger studies will be needed to measure the prevalence of orthostatic intolerance among athletes with prolonged underperformance at all levels of competitive swimming, as well as in other sports.


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