Terms of Use — Homo Optimus

Last updated: [01-09-2026]

What this newsletter is

Homo Optimus is a personal newsletter published by Yannick Delvaux. It documents self-experiments on health, fitness and daily habits, conducted on one person: me.

By reading it, you agree to the terms below.

This is not medical advice

Nothing published here is medical, psychological, nutritional, or professional health advice, and nothing here is intended to diagnose, treat, cure, or prevent any condition.

I am not a doctor, a physiotherapist, a dietitian, or a medical professional of any kind. Where I hold relevant qualifications — for example as a breathwork instructor — those qualifications do not make me a clinician, and nothing here should be read as a clinical opinion.

If you are considering changing anything about your health, your training, your medication, your diet, or your sleep, speak to a qualified professional who knows your situation. That is particularly important if you are pregnant, have a diagnosed medical condition, take prescribed medication, or have a history of cardiac, respiratory, or mental health problems.

What n=1 means, and why it matters

Every experiment described here has a sample size of one. That is the whole point of the project, and it is also its central limitation.

A result from a single person, over a few weeks, with no control group and no blinding, is not evidence that something works. It is evidence of what happened to me, once. It may be explained by the intervention, or by the weather, my workload, how well I slept, the season, the placebo effect, measurement error, or coincidence.

I report what I measure as honestly as I can, including the experiments that produce nothing. Please do not read any of it as a recommendation, and please do not treat my results as a reason to change anything about your own health without proper advice.

Breathwork, breath-holding and related practices

Some experiments involve breathing techniques, breath retention, cold exposure, or similar practices.

Never practise breath-holding or intensive breathing techniques in or near water, while driving, while operating machinery, or while standing. People have drowned doing this. Sit or lie down, on a soft surface, with nothing sharp nearby.

These practices can cause dizziness, fainting, tingling, muscle spasm and, in some people, more serious effects. They are not appropriate for everyone, and some conditions rule them out entirely. If you have any cardiovascular condition, epilepsy, a history of fainting or seizures, uncontrolled blood pressure, a respiratory condition, or are pregnant, do not attempt them without medical clearance.

If you choose to try anything described here, you do so entirely at your own risk.

Devices and measurements

I use consumer wearables, apps, and consumer-grade measurement hardware. These are not medical devices, they are not calibrated to clinical standards, and their readings can be inaccurate.

Nothing measured or reported here should be used to assess your own health. If a wearable tells you something concerning about your body, take it to a doctor, not to a newsletter.

Content, accuracy and changes

I write this in good faith and try to get it right. I cannot guarantee that everything here is accurate, current, or complete. Scientific understanding changes, I make mistakes, and older posts may not reflect what I would write today.

Where I correct a significant error, I say so. Where I change my mind, I try to say that too.

Your own use of this newsletter

You are welcome to read, share and quote this newsletter with attribution and a link. You may not republish whole posts, sell the content, or present it as your own.

Comments and replies are welcome. I may remove comments that are abusive, spam, or that give medical advice to other readers.

Limitation of liability

To the fullest extent permitted by law, I accept no liability for any loss, injury, or damage arising from your use of, or reliance on, anything published here. You are responsible for your own decisions about your own body.

Nothing in these terms limits any liability that cannot legally be limited.

Platform

This newsletter is published on Substack, and your use of the site is also subject to Substack’s own terms of use and privacy policy.

Governing law

These terms are governed by Belgian law.

Contact

Questions about any of this: blog@homo-optimus.com.