Systemic Conditions

01What the measurements show

The Numbers Behind the Well Athlete Who Tests Abnormal

Eight findings that show trained physiology sitting outside the population range while nothing is wrong.

02Conditions as variables

A Systemic Condition Is a Managed Variable, Not a Disqualification

A systemic condition in an athlete is a managed variable, and the entire purpose of the pre-participation evaluation is to map it precisely. The evaluation screens for anemia, airway disease, diabetes, epilepsy, cardiac risk and skin infection so that each can be dosed, fueled and monitored rather than guessed at. Elite athletes compete and win with every one of them.

The record is blunter than that. From 2002 the International Olympic Committee required objective testing before an athlete could use an inhaled beta2 agonist, which produced a clean register of who actually had asthma. Asthmatic athletes then outperformed their peers at both the Summer and Winter Games from 2002 to 2010 McKenzie 2011.

What separates the athlete who thrives from the one who falters is rarely the diagnosis itself. It is the quality of the system built around it. A condition that is measured, tracked and accounted for in training load becomes background noise. A condition that is ignored becomes the thing that ends a season. The work is to know the numbers cold and design around them.

Handled that way, systemic conditions turn into variables inside the program rather than verdicts passed on it. The nervous system underneath the diagnosis is one of those variables, and it is the one this practice reads.

Why the numbers are harder to read in an athlete

Knowing the numbers is harder than it sounds, because the numbers were not written for athletes. A reference range is built from a sampled population, and almost nobody in that population trains twenty hours a week. Sustained training moves resting heart rate, chamber size, blood volume, hematocrit and airflow well outside the interval the laboratory prints beside the result.

So the reading goes wrong in both directions. A well athlete gets flagged for a finding that is pure adaptation, which is why the 2010 European electrocardiogram criteria raised suspicion in 40.4 percent of black athletes Sheikh 2014. And an athlete who has genuinely drifted stays inside the range because they started above it. Both errors come from using a population as the reference instead of the athlete.

The yield of the pre-participation evaluation, and the argument over whether it should include an electrocardiogram at all, belongs to The Pre-Participation Exam. What follows here is the interpretation problem the evaluation hands over: three body systems where trained physiology reads as disease.

03The athlete electrocardiogram

The Trained Heart Reads as Abnormal on a Population Electrocardiogram

The resting electrocardiogram of a healthy trained athlete carries findings that would be worked up in a sedentary adult. One study recorded twelve-lead traces from 1,000 junior elite athletes and 300 controls matched for sex, age and body surface area Sharma 1999. Sinus bradycardia ran at 80 percent against 19 percent, and sinus arrhythmia at 52 percent against 9 percent.

Conduction slowed too. Mean PR interval ran 153 milliseconds in athletes against 140 in controls, QRS duration 92 against 89, and QT duration 391 against 379. ST segment elevation appeared in 43 percent of athletes and 24 percent of controls. Voltage criteria for left ventricular hypertrophy were met by 45 percent of athletes and 23 percent of controls.

None of that is a disease. It is what a heart looks like after a long history of moving a great deal of blood at rest and an enormous amount under load. The vagus holds the rate down between efforts, and the chamber that fills more slowly generates more voltage at the chest wall.

The finding that separates the two groups

Athletes and controls stopped resembling each other at one point in that dataset, and it is the point that matters clinically. Not one athlete with voltage criteria for hypertrophy also showed left axis deviation, ST segment depression, deep T wave inversion or pathological Q waves Sharma 1999. The markers of pathological hypertrophy were absent while the voltage of adaptation was everywhere.

Minor T wave inversion in leads V2 and V3 turned up in 4 percent of athletes and 4 percent of controls, so it discriminates nothing. Elsewhere it was absent in controls and present in 0.4 percent of athletes. The authors treat T wave inversion outside V2 and V3 in an athlete over 16 as an indication for further investigation.

Why the criteria were rewritten twice

Reference criteria for the athlete electrocardiogram have been revised twice in a decade because the first versions flagged too many well athletes. The 2010 European recommendations raised suspicion of a cardiac abnormality in 40.4 percent of 1,208 black athletes and 16.2 percent of 4,297 white athletes Sheikh 2014.

The Seattle criteria brought that to 18.4 and 7.1 percent. A further refined set, which excludes several isolated patterns, brought it to 11.5 and 5.3 percent. All three sets identified 98.1 percent of the 103 young athletes with hypertrophic cardiomyopathy in the same comparison. Specificity in black athletes rose from 40.3 to 84.2 percent without sensitivity falling.

An international group of sports cardiologists met in Seattle in February 2015 and published the resulting standard as the international criteria for electrocardiographic interpretation in athletes Drezner 2017. The stated purpose is physician education that distinguishes normal physiological adaptation in athletes from distinctly abnormal findings suggestive of underlying pathology.

Read that purpose again as a statement about reference ranges. The instrument did not change. The population it was being read against did, and the false-positive rate fell by roughly two thirds.

04Adaptation or disease

Adaptation Enlarges the Heart in Proportion; Disease Moves One Part Out of Proportion

Athlete's heart and cardiomyopathy are told apart by proportion, not by any single measurement. Echocardiography in 1,309 elite Italian athletes across 38 sports recorded left ventricular end-diastolic cavity dimensions of 43 to 70 mm in men and 38 to 66 mm in women Pelliccia 1999.

Just over half sat inside generally accepted normal limits. In 185 athletes, 14 percent of the cohort, the cavity exceeded the 60 mm cut-point that raises the question of dilated cardiomyopathy in a clinic. Every one of them had global systolic function within normal limits and no regional wall-motion abnormality. They stayed free of cardiac symptoms and of any drop in performance for 1 to 12 years, a mean of 4.7.

Body surface area and endurance sport were the determinants of cavity size. The heart grew because it was asked to move more blood per beat, and it grew as a whole.

What disproportion looks like

The distinction becomes concrete in the wall-thickness gray zone. Screening of 3,500 asymptomatic elite athletes with a mean age of 20.5 years found left ventricular hypertrophy of 13 to 16 mm in 53 athletes, 1.5 percent of the group Basavarajaiah 2008. In 50 of those 53 the cavity was dilated and diastolic function was normal, which marks the hypertrophy as physiological.

Three athletes, 0.08 percent of the cohort, had a thick wall with a cavity that had not dilated, plus deep T wave inversion. That is the signature of disease: one chamber wall enlarging while the chamber it surrounds does not. None of the three had other features of hypertrophic cardiomyopathy or an affected first-degree relative.

Weigh the base rates before reading any single athlete's echocardiogram. In the gray zone that worries a clinician most, physiological hypertrophy outnumbered possible disease by roughly 17 to 1.

Detraining as the deciding test

One of those three athletes agreed to stop training for 12 weeks. The electrocardiographic and echocardiographic changes resolved, confirming physiological hypertrophy Basavarajaiah 2008. Adaptation reverses when the input that produced it is withdrawn. A cardiomyopathy does not.

This is why the international criteria are written as two lists rather than one threshold: patterns that are training-related and expected, and patterns that are abnormal and require investigation Drezner 2017. The finding is the same shape on the paper. What differs is the physiology it belongs to.

The autonomic half of that remodeling, the vagal restraint that holds an athlete's resting rate near 40 beats per minute, is covered in Cardiac Neurology. Its day-to-day readout is the subject of Heart Rate Variability.

05Anemia and ferritin

The Endurance Athlete's Low Hematocrit Is Usually Dilution, Not Anemia

Trained endurance athletes run a lower hematocrit than sedentary people, and the label sports anemia attached itself to that observation. It is not anemia in a clinical sense. Athletes carry an increased total mass of red blood cells and hemoglobin, and the hematocrit falls because plasma volume rises further and faster than red cell volume Mairbaurl 2013.

The size of the gap is worth stating in numbers. Total hemoglobin mass measured by carbon monoxide rebreathing came to 15.4 g per kilogram in professional cyclists at sea level against 11.0 in untrained controls Schmidt 2002. Blood volume ran 107.0 mL/kg against 78.3. VO2max in the same groups was 68.2 against 45.3 mL/kg/min.

So the athlete whose hematocrit reads low is carrying roughly 40 percent more hemoglobin than the person whose hematocrit reads normal. The ratio moved. The oxygen-carrying capacity moved the other way. A concentration is a fraction, and training changed the denominator.

Real iron loss still happens, through a mechanical route

Iron carries oxygen, and a genuinely depleted athlete is starving working muscle of the fuel it needs. Endurance exercise does destroy red cells. They rupture mechanically as they pass through capillaries in contracting muscle, and they are compressed in the foot soles during running or the palms in weightlifting Mairbaurl 2013. Foot strike hemolysis is the name that stuck for the second route.

Mostly senescent cells break, which lowers the mean age of the circulating population. Iron also leaves in sweat and through the gut, so a distance athlete runs several small losses at once.

That younger population releases oxygen more readily and deforms more easily, so the destruction carries a benefit alongside the loss. Absorption is the other half. Exercise raises hepcidin, the hormone that governs how much dietary iron crosses the gut wall, and a raised hepcidin closes that door for hours after a session Sim 2019.

Iron deficiency has been reported in roughly 15 to 35 percent of female athlete cohorts and 5 to 11 percent of male athlete cohorts Sim 2019. Sex hormones, dietary carbohydrate availability, training load and altitude exposure all move iron status in the same athlete.

Ferritin, and the cut-off that had to be derived

Serum ferritin reflects iron stores and is the number that matters, because the body regulates absorption against its own reserves. The cut-off that defines deficiency in an athlete has never been settled. One group sampled 37 to 43 male college runners every month from March to December and derived the threshold from the curvature of the relationship between ferritin and total iron binding capacity Kobayashi 2020.

Monthly values landed between 35.0 and 45.0 ng/mL, averaging 37.2, and the authors proposed 40.0 ng/mL for runners. Standard laboratory thresholds sit well below that. An athlete flagged as normal by the population number can be deficient by the number derived from athletes.

What iron treatment actually did

Pooling 17 studies of iron-deficient endurance athletes who were not anemic, iron treatment produced large effects on serum ferritin, serum iron and transferrin saturation Burden 2015. Effects on hemoglobin concentration and on VO2max were moderate, with a standardized mean difference of 0.610 for VO2max. Treatment beyond 80 days had the least effect on ferritin.

So supplementation is a real option with a measured response, and it is the physician or dietitian who orders the panel, reads it and decides. Vitamin C sharply increases the absorption of dietary iron, which is why the practical version is monitored intake matched to ferritin and to the oxygen demand of the sport.

What belongs here is the reading. A hematocrit alone cannot distinguish an expanded plasma volume from an emptied iron store. Only ferritin, tracked against the athlete's own prior values, separates them.

06Breathing under load

Exercise-Induced Bronchoconstriction Is Found by Spirometry, Not by Asking

Exercise-induced bronchoconstriction is the transient narrowing of the airways that follows hard effort, and it is the preferred term over exercise-induced asthma because it does not require chronic airway inflammation. It occurs in people with asthma and in elite athletes who have none Parsons 2013.

Symptoms will not find it. Among 158 elite athletes, most of them cold-weather competitors, a sport-specific and environment-specific challenge left 26 percent with a postexercise FEV1 drop greater than 10 percent Rundell 2001. Two or more symptoms were reported by 39 percent of the athletes who bronchoconstricted and 41 percent of those who did not.

Post-race cough was the one symptom reported significantly more often by the test-positive group. Sensitivity and specificity analysis showed self-report failing in both directions at once, generating false positives and false negatives in the same cohort. The authors conclude that diagnosis requires spirometry with an exercise or environment-specific challenge alongside the history.

The reference-range trap in the lung

Resting FEV1 in those athletes measured 114 to 121 percent of predicted, and did not differ between the groups Rundell 2001. Start a tenth above the population prediction, lose a tenth to bronchoconstriction, and the postexercise value lands close to where an untrained person's healthy baseline would be.

That is why the diagnostic criterion is a fall from the athlete's own pre-challenge value rather than a comparison with predicted values. The same investigators derived postexercise lower limits from athletes who were normal on challenge: minus 7 percent for FEV1, minus 12.5 percent for FEF 25 to 75, and minus 18 percent for peak expiratory flow.

What the trigger actually is

The stimulus is water, not cold. Hard continuous exercise in cold, dry or polluted air drives water loss across the airway surface, and that evaporative loss raises the osmolarity of the airway surface liquid Anderson 2023. The osmotic shift makes mast cells release histamine, prostaglandins and leukotrienes, and those mediators constrict the bronchioles. The signature on testing is a measurable drop in FEV1.

Winter endurance sport therefore concentrates cases, because it maximizes both minute ventilation and the dryness of the air being conditioned. Swimming in a warm humid pool provokes far fewer events at the same effort. The trigger is predictable, and a predictable trigger can be planned around.

Timing the dose, and the anti-doping question

A short-acting beta2 agonist such as albuterol, taken before exercise, carries a strong recommendation for all patients with exercise-induced bronchoconstriction Parsons 2013. For athletes who still have symptoms on that regimen, strong recommendations cover a daily inhaled corticosteroid, a daily leukotriene receptor antagonist, or a mast cell stabilizing agent before exercise.

Attacks arrive during and after the effort, so the dose goes in ahead of the effort rather than in response to it. That is what makes the condition a scheduling problem instead of a ceiling.

An athlete who knows the trigger pattern and times the dose does not lose training to the lungs. The prescribing and the World Anti-Doping Agency paperwork belong to the physician: only two inhaled beta2 agonists were permitted under the 2010 list change, and the rest remain prohibited McKenzie 2011. Airway disease as a regulated state in the wider population is carried by the asthma research page.

07Recognition and referral

The Role Here Is Recognition and Referral, and Speed Is Part of the Dose

A chiropractic practice does not diagnose or manage a systemic disease. It recognizes when a finding belongs to physiology rather than to training, and it moves that athlete to the clinician who owns the question. In a cohort of 3,500 elite athletes, three carried a pattern that needed cardiology Basavarajaiah 2008. Knowing which three is the whole job.

Referral is instrument selection, not a limitation. The Unified Model of Tone places every intervention on one continuous axis of magnitude, and choosing correctly on that axis includes choosing the larger magnitude when the situation calls for it. When a distortion has descended past what any surface input can reach, the larger magnitude is the correct one, and delay becomes its own kind of harm.

That principle cuts both ways, which is why it is a dosing rule rather than a deferral. An athlete sent for cardiology because a screening criterion was written for sedentary adults pays for that referral in weeks of lost training and in the fear that follows a flagged heart. Reading the criteria correctly is part of the same skill as escalating fast.

What is measured here, and what is measured elsewhere

What this practice measures is the athlete's central integrative state: the balance of excitation and inhibition a neuron, a pathway and a whole nervous system settle into. It is read through joint position sense, eye movements, balance, reaction time, and how the autonomic nervous system recovers after a load. That reading is drug-free and anti-doping compliant, which matters for a competitor under testing.

Several conditions this page's title could cover are handled in full elsewhere in the section. Glucose and insulin management in the diabetic athlete, what aerobic work does for the epileptic brain, and sickle cell trait in sport belong to Special Populations. On-field collapse, cardiac arrest and the emergency action plan belong to Emergency and Field Care. Low energy availability belongs to Body Composition, and cortisol dynamics with the load they encode belong to Stress, Cortisol and the HPA Axis.

The practice works alongside team physicians, cardiologists, pulmonologists and dietitians as an equal with a different instrument. The heart on the echocardiogram belongs to the cardiologist. The regulation that heart sits inside is a shared problem, and it is measured every week by staff who already own the equipment.

08What we corrected

Three Claims Removed and One Mechanism Updated

Three claims about the athlete previously carried here could not be traced to a source. Endurance training raising iron demand by roughly 70 percent is the first. Heme iron absorbing at up to about 35 percent against 2 to 30 percent for plant iron is the second. Both are gone, and the mechanical hemolysis and hepcidin account above replaces them.

The claim that heavy iron supplementation carries real toxicity risk went with them, for the same reason. Dosing decisions belong to the clinician holding the blood panel, which is the accurate version of the point the old sentence was reaching for.

The airway section previously gave two triggers: water loss across the airway surface, and post effort rewarming of the cooled airway, which floods the lining with blood. The current mechanism proposal is the first of those. Evaporative water loss raises the osmolarity of the airway surface liquid, and mast cells release the mediators that constrict smooth muscle Anderson 2023.

The diabetes and epilepsy figures the page carried now live on Special Populations, which covers those conditions in full. They include the share of diabetes cases that are Type 1 and the age distribution of first seizures. A quotation attributed to Dr. Jason Dulberg was not drawn from anything he said or wrote, and it has been removed.

09The model's claim

One Baseline, Read Through Four Instruments

Physiology first, then the reading. The bradycardia, the enlarged ventricle, the diluted hematocrit and the falling FEV1 are measurements. Sharma, Pelliccia, Schmidt and Rundell recorded them in athletes who were well, and those records hold whatever anyone later concludes about regulation.

The Unified Model of Tone claims something the measurements themselves do not. A reference interval is a statement about a sampled population, and it carries no information about where inside their own regulation any one athlete is sitting. The trained athlete is the case that makes the gap visible in four organ systems at once.

Three fields already made the same correction separately

Sport cardiology rebuilt its electrocardiogram criteria around athletes, cutting the flagged share in black athletes from 40.4 to 11.5 percent Sheikh 2014. Sport pulmonology derived postexercise lower limits from athletes who were normal on challenge, at minus 7 percent for FEV1 Rundell 2001. Sport nutrition derived a ferritin threshold of 40.0 ng/mL from runners rather than from laboratory norms Kobayashi 2020.

Three fields, three decades, three separate corrections, each treated locally as a technical fix to one test. The model reads them as one correction made three times: the reference has to be the athlete. That is a claim about how an athlete's physiology is organized rather than a claim about what any treatment does.

The prediction this page makes

Take one squad. At preseason and at four points across the season, record four things in the same athletes. The postexercise fall in FEV1 as a percentage of that athlete's own pre-challenge value. RMSSD from a morning recording. Serum ferritin. And the time taken to return to resting heart rate after a standardized load test.

Score every value as a deviation from that athlete's own preseason figure rather than against a population interval. The model predicts the four deviations covary within athlete, because they are four instruments pointed at one regulatory state. It further predicts the within-athlete score flags the drifting athlete earlier than any population cutoff does.

If postexercise FEV1 fall, RMSSD, serum ferritin and time to return to resting heart rate are shown to move together within the same athletes across a season, the unification claim is confirmed.

10The tone reading

What the Abnormal Reading Is Actually Reading

Three signatures of tone appear on this page, each inside a test a medical team already orders.

The other foundations run through the same three systems. Time course is why detraining is diagnostic, since 12 weeks without training reversed the changes in the one athlete who tried it. Load is the training demand that moved every reference value on this page in the first place. Gain appears at the gut wall, where exercise raises hepcidin and narrows how much dietary iron gets through. Prediction is the athlete's own preseason figure, the expectation every later reading is scored against. Coupling is plasma volume and red cell mass moving together, which is why a hematocrit read alone says almost nothing. Oscillation is respiratory sinus arrhythmia, present in 52 percent of junior elite athletes and 9 percent of controls. The full framework is set out in the Unified Model of Tone.

11Where this sits

How This Page Relates to the Rest of the Library

Seven places this argument continues, each with the claim that earns the link.

12Questions athletes ask

Questions Athletes Ask

13The sources

References

14 primary sources, each linked to its record. Figures quoted on this page were checked against the published abstract.