No experiments without data. I trust my feelings, but not enough to have them objectively support this project. Which is why I have quite a few wearables and measuring devices that will provide the data for me.
Last week I talked about “the confounders”. This week I will talk about the tools.
It is worth noting that this equipment will provide me with numbers that might not necessarily be 100% accurate. This is not that big an issue, because I am looking for trends, not ad hoc information. Consistency will be key, so I will be using the same device(s) for the same measurements.
I will describe all items in roughly the following order: what it is and what it measures, what I will use it for and finally how much I trust it.
The list below is up-to-date for September 2026. If anything changes, during an experiment or in between experiments, I will mention it and afterwards also adapt this list so it will remain a reference document.
If you just want to know what device I use to measure which metric, scroll to the overview at the bottom.
AI:
My partner in crime, Claude by Anthropic. If you have not heard of Claude it is Artificial Intelligence, just like ChatGPT. It does not measure anything, but it can help me with just about everything else. I do not trust it blindly and I try to be as clear and specific as possible.
Claude’s own summary of the problem, which I agree with: language models produce fluent, confident text whether or not it is correct, so anything factual gets checked.
I use Claude for everything I would otherwise have to ask other people for. It helps me with brainstorming, checking my reasoning and pointing out things I had not considered. It helps me with technical aspects, like device specifications, and it proof-reads my texts.
While it would massively simplify things and save me a bunch of time, Claude does not write my texts …
Log app:
Last week I mentioned I would be logging a lot of things. One of the first things I asked Claude was to help me with an easy app for logging the things that matter. These include sleep data, how I subjectively feel, TM sessions, training and alcohol intake, among others. I wanted it on my phone, so I can use it everywhere and it registers immediately. Writing it down and digitising it later is not a habit that would work for me. The downside is that I have to use my phone almost immediately after waking up.
I have been using this app since mid-August, so I currently have a month of baseline data. The data is kept online, not locally. So I will not lose anything if something happens to my phone.
This app is the only tool I use that I have complete control over. I decide what goes in there and I adapt it if I feel it is not good enough. I will however not change the structure of the log during an experiment. I do not wish to fool myself or others.
While writing this I discovered I can adapt past inputs. I do not want to risk changing my inputs because I feel like I was perhaps wrong, so I will improve the app to make this impossible. As soon as I have fixed this, I will mention it!
Garmin Fenix 5X:
One of my oldest devices. I have had the watch since mid-2018, so it is perhaps not my most modern device, but it still does the job! It is bulky, sturdy, has already been through a lot, and the battery life is still very decent.1
The main thing it measures is heart rate. Besides that it also measures movement, steps, ambient temperature, barometric pressure and location-related data. From these it then derives information like training status and load, VO2 max, recovery, stress score, sleep stages and calorie estimates.
I mostly use it to track my sport sessions, but it is also a back-up for sleep and my step count. I have a chest strap I can use in combination with the watch to get more accurate readings. This is mainly useful for running. The strap is also my best bet if I want to get heart rate readings.
Since the watch’s optical sensor only measures on my wrist (I only wear the strap for running or biking), it does not provide me with the most accurate readings. The wrist moves a lot and is not ideal for optical sensing. It is still very useful for trends though and as a back-up for my ring.
For any sports experiments the watch will be my primary device.
Circular Ring 2:
The most popular and well-known smart ring is probably the Oura ring. Circular Ring 2 is a similar concept, except that there is no subscription needed after you buy the ring. After some research and since I did not want another subscription, I decided to back the Kickstarter project for the ring.
I have had a problem with my ring and then many problems with Circular’s customer support (I will not digress; it would not be healthy), but it has been up and running now since mid-August.
For such a tiny object, it is packed with sensors (PPG, thermistor and accelerometer) and provides a lot of readings. Sleep, Heart Rate Variability (HRV), Heart Rate (HR) and Resting Heart Rate (RHR), Breathing Rate (BR), temperature, SpO2, steps, to name a few. Since the last update it even measures Blood Pressure (BP). Since this is an estimation, it requires calibration with a BP reader.
The main reason I got the ring was to track my sleep. It never felt like the Garmin watch was providing me correct readings, so I wanted a second opinion. The Circular Ring will be my main “track everything” tool. I wear it non-stop with only a few exceptions, mostly related to manual labour, where it could get damaged.
For certain measurements, like (R)HR, HRV and sleep, the ring is better than the watch. The finger is a better location for optical sensors. For others, like movement or GPS, it is similar or worse. I also do not have absolute faith in the data it provides, but I will wear it more than my smart watch. These reasons are why I have decided to use it as my main device. Let’s hope it does not prove a risky bet, given the track record.
HeartMath emWave pro:
An interesting biofeedback device that focuses mainly on HRV. The emWave pro plugs into a computer USB port and has a wired optical sensor clip you attach to your ear lobe. This is a good location for optical readings, as long as it is not too cold. Since it is wired and you cannot move too much, the output is more stable. It gives a live reading of your HR and HRV and scores your coherence.
How exactly? By measuring the intervals between heartbeats, down to the millisecond. These intervals are never identical; the variation is called Heart Rate Variability. It can be irregular or smooth like a sine wave. The smoother it is, the higher your coherence score will be.
I use it to practise heart coherence breathing or to measure how coherent I am during certain activities, for example Transcendental Meditation.
The emWave pro uses a proprietary algorithm and has not been independently validated, but it has already been used in clinical trials. I trust the data, but I also know there are a lot of factors that can have an influence.
A few remarks:
There are different challenge levels. The higher the level, the more difficult to score a high coherence. I will clearly define what I use before starting an experiment.
Breathing directly influences your HR and can be used to manipulate readings. A BR of five to six breaths per minute (called coherent breathing) produces a high coherence score. This also means you can use your breath as a tool to train your coherence.
Omron M2:
A simple Blood Pressure reader. It is a clinically validated device, meaning it has been tested independently against standards set by the European Society of Hypertension. It gives me readings of my systolic and diastolic blood pressure and my pulse.
It is my primary device for measuring my BP and for this I do trust it quite a bit. Although it is clinically validated, the readings I get will be very dependent on when I take them.
I also use it to calibrate my Circular Ring once per month (required by the app), so that it can serve as my secondary BP reader, when I do not have the Omron.
Nokia Body+:
A simple smart scale that measures weight, fat percentage, total body water, muscle mass and bone mass.
I use it as my primary device to track my weight and for this I trust the scale, since it measures it directly. All the rest is estimated and nice to know, but I do not put too much weight on these numbers.
Medisana PM100 Connect:
A certified medical pulse oximeter. It meets certain regulatory requirements, but it has not been independently tested. You attach it to a finger and then get your oxygen saturation, heart rate and perfusion index (PI). It is meant for spot checking and not continuous monitoring. Since it takes time for the blood to travel to the extremities, there is a twenty- to thirty-second lag on the data you get.
I bought it while I was following my breathwork course. It was recommended (not this specific one, but just a pulse oximeter) to track some metrics while practising. It can show how long you stay saturated even while holding your breath and how your heart rate is influenced.
I trust the data, but with a caveat. The PM100 is attached to the fingertip, so if the blood flow is not good, vasoconstriction caused by breath holds for example, the reading might be off. The PI can be of help here. If it is low, trust the readings less.
CAROL bike:
The CAROL bike is basically a home trainer on steroids. It uses AI to adapt the training protocols to the user. The selling point is the Reduced Exertion High-Intensity Interval Training (REHIT) protocol. Some easy biking, two flat-out twenty-second sprints all in a minimum of five minutes. According to the manufacturer this is similar to a 45-minute run and could improve your VO2 max by twelve percent in eight weeks.
It measures your power output directly and your HR with a provided chest strap. It can also provide a VO2 max estimate, by either a ramp test or a submaximal test. The former mirrors lab protocols and is more trustworthy than the latter. Good for follow-up, not as an absolute value.
I bought the bike since the claim in the first paragraph intrigued me. As mentioned in last week’s post, I use it for my cardio training. While I think it certainly has its benefits and it saves me a lot of time, I have yet to properly test the claims. This is definitely on my radar.
Superhlth:
Superhlth is one of those holistic health-data tracking apps. It combines all your input (DNA, blood results, microbiome, wearables, etc.) and provides an overview of how healthy you are and gives advice based on AI. The company around the app also sells DNA, blood and microbiome tests.
Full use of the app requires a subscription; I just use the free version. I want to know how solid it is, before I get yet another subscription. Superhlth does not measure anything, but it collects data and then produces output like the Superhlth score, based on sleep, energy, nutrition and activity. It also gives an estimate of your biological age and shows you a “digital twin”. Biological age can be nice and flattering (or the opposite), but there is no standard way to calculate it.
I use it on a daily basis to log my food and nutrient intake. It uses AI protocols to analyse meals and give an overview of the nutrients you are getting. I doubt it is always correct, but it allows me to be lazy or, uhm let’s say, efficient.
I have also ordered their DNA test and track my blood work with the app. I do not regard the app’s interpretation as the absolute truth, but I find it very interesting and informative.
Again, the trend is what matters. The measurements and tests the app uses are sound, but they are interpreted by a proprietary AI model, which I do not yet trust fully. It is only my primary tool for food intake, not for anything else.
Overview:
A list of the metrics and what device I primarily use to measure them. This will be fixed during experiments and if it changes from one experiment to another, it will be documented. The current list is up-to-date as of September 2026.
Coherence: emWave Pro
HRV: Circular Ring 2 (rest and overnight), emWave Pro (during sessions)
HR: Circular Ring 2 (rest and overnight), Garmin Fenix 5X (during training)
RHR: Circular Ring 2
BR: Circular Ring 2
Sleep: Circular Ring 2, Garmin Fenix 5X (back-up)
BP: Omron M2, Circular Ring 2 (travel)
SpO2: Circular Ring 2 (rest and overnight), Medisana PM100 (spot checks)
Weight: Nokia Body+
Training load and sports metrics: Garmin Fenix 5X
Power output and VO2 max: CAROL bike
Food and nutrient intake: Superhlth
Everything self-reported: log app
For anyone (from Belgium) that might be interested in getting a Garmin device, check if your employer also participates in “Benefits at work” or something similar. I know Defense and other government agencies do and you can get a decent discount!