I'm making a character and trying to be biologically accurate. Said character has transfusion-dependent anemia (from Gunther disease/congenital erythropoietic porphyria) so I suppose exercising would be hard by default, but what are some other conditions that would make physical training unhealthy? Ideally, I'm trying to make it so even light exercising is bad, but severe would cause vomiting/fainting/etc.

I posted this question on biology, but someone suggested I try asking here instead. I think that the question is less relevant there, so might as well ask here since I didn't get an answer anyway. I apologize for asking the same question twice.

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    There are literally dozens of possibilities and the big ones like heart failure should be easy to find with google. The person who referred you here should have mentioned that we expect you to do some homework on your own first.
    – Carey Gregory
    Dec 26, 2019 at 5:40
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    Heart failure comes in degrees and someone in class 4 isn't going to be doing any exercising. Almost any disease/condition will benefit from some degree of exercise, so if you exclude that then you're excluding almost everything. You really need a condition that makes any level of exercise actually harmful? (And not just temporarily, like after surgery or such.)
    – Carey Gregory
    Dec 26, 2019 at 6:41
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    What is the scenario? Is someone making an exercise and experiences symptoms, or someone is not making an exercise to avoid symptoms? What does the effect of symptoms need to be: just stopping the exercise, not being able to perform a planned task, experiencing pain or having a permanent damage caused by exercise? Also can you give some hint of a broader context?
    – Jan
    Dec 27, 2019 at 11:37
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    Would you check for "mitral valve prolapse" and "cystic fibrosis?" If it suits to you, I can comment further if needed.
    – Jan
    Dec 28, 2019 at 15:03
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    You know this could be a genetic disease. (Medical genetics). Who knows? Get a full workup for this character. Off the bat the character could try some coq10 and melatonin (melatonin for mitochondria). Under a physicians supervision. Could be some mitochondrial issue.
    – Gordon
    Dec 28, 2019 at 22:07

2 Answers 2


If you're looking for a disease with childhood onset that requires exercise restriction, Long QT Syndrome (LQTS) may work, specifically LQT1. Here is a lay overview. For more detail, see this review. I'm not a cardiologist, and have never seen a patient with LQTS, so I'm honestly not sure how variable the presentation is. Generally, for LQT1, exercise or stress induced tachycardia can cause a life threatening arrhythmia called torsades de pointes and sudden death.

Treatment of LQT1 includes avoidance of stress, exercise restriction, and beta blockers. As discussed in the linked review above, certain extreme phenotypes may not be fully controlled with beta blockers. Pain, nausea, or perceived exercise intolerance (e.g., fatigue), the symptoms you mentioned in your comment, are not part of the described symptom complex. Rather elevated heart rate leads to the malignant arrhythmia. The symptom complex is that of the arrhythmia (palpitations, fainting, seizures, and death).


Here are medical conditions that come to mind, each with different symptoms:

  1. Severe exercise-induced asthma. Symptoms will be severe wheezing, O2 drop, potentially even death. Long-term anti-inflammatory medications can prevent exacerbations, though exacerbations can still be triggered in specific situations. Imagine a deconditioned character, in fight-and-flight, running from danger in cold weather, and especially with bronchi inflamed from a respiratory infection.
  2. POTS - postural orthostatic hypotension. A type of dysautonomia, a likely autoimmune condition that can trigger O2 drops, brain fog, nausea, fainting from minor exercise, or (in very severe cases) even from standing up and staying upright. It used to be thought that graduated exercise would help everyone. Not true.
  3. Chronic fatigue syndrome. Often infection-triggered, likely autoimmune, with antibodies to adrenergic receptors (adrenergic - think adrenalin). Causes post-exercise malaise, meaning dysproportionately severe symptoms for days/weeks after overdoing things, including much increased odds of fainting from POTS, overwhelming fatigue, GI symptoms (nausea, inability to digest..). Depending on the patient, the "overdoing" may be physical or cognitive, ranging from doing a college entrance exam, to cooking for a family visit, to walking around the block.
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    Systemic Exertion Intolerance Disease (SEID) has been proposed as an alternative name for chronic fatigue syndrome, see CDC website and 2015 Institute of Medicine report called Beyond Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Redefining an Illness.
    – Mousey
    Jul 4, 2020 at 13:45

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