The most common health tracking system people use is the "daily diary". At the end of the day, they make a record of what they did and how they felt, using a variety of tools, e.g.:
When I had back pain, I used "daily diary" systems like this for years. Although I put lots of effort, in the end I found that the data was not of much use to me. Here is what I learned.
The daily diary sounded so easy at first. I just would take 1 minute at the end of my day to fill out a checklist. I set up an alert at 11pm. But I ended up skipping it many nights. Often the alert popped up when I was busy with something, so I would ignore the alert or procrastinate until I was too tired and fell asleep.
All of us already have enough chores in our daily life: things that "only take a minute", that we should do at some point in the day, but that end up nagging at us. Reply to your messages and emails, put on moisturizer, take your daily vitamins and supplements, do your stretches, start the dishwasher, put your clothes in the hamper, sort through your mail, pay your bills, 5-minute daily meditation, etc.
If you are like most people, you already feel some guilt about not getting all these things done. So, why add another item to this pile? The fact that it only takes 1 minute is irrelevant. The scarce resource is not the time it takes, but the mental energy and willpower to stop procrastinating and do it now.
When you are tired in the evening, it is bothersome to fill out a survey about your day. It takes a surprising amount of mental energy, e.g.:
It's human nature to follow the path of least resistance, which means you will will eventually procrastinate or forget to do it.
For example, let’s say your daily diary shows that on June 1 you did a lot of stretching and had increased pain. But you don't know what came first, the stretching or the pain. Maybe the pain started first, so you did stretches to relieve the pain. Or maybe you stretched in the morning, and that caused your pain to flare up for the rest of the day. You might conclude that stretching makes your pain worse when in fact it's the opposite!
Or, let's say your records show that on Sunday you took a medication, and on Monday you had a stomach ache. Since it could be any time on Sunday and any time on Monday, those two events could be 1 hour apart, or almost 48 hours apart (e.g. early morning Sunday and late night Monday). When you try to analyze your data later, you may realize the data is junk since it is so imprecise.
For most symptoms, recording once a day is not the most appropriate interval. Some symptoms fluctuate many times a day whereas others change on more of a weekly basis, etc.