If your read on an NIR LED session is just it felt a little better today, you have no way to tell whether you are actually improving or just having a good day. A pain diary turns that vague impression into numbers and patterns you can actually check.
This guide lays out, in practical terms, what to record, when to record it, and how to read weeks of entries once they pile up, so you stop guessing about whether the device is doing anything.
The need for this is sharpest if you are rotating the device across different body areas or experimenting with wavelength and duration to find what works for you. Without a structured log, there is no real way to tell which combination actually produced a better result versus which one you simply remember more favorably. Keep at the routine below for two to four weeks and your next round of settings will be based on something more solid than a hunch.
Why a Pain Diary Matters
Why Recording Beats Remembering
People are not good at recalling how their body felt several days ago. Sensations that fluctuate a lot, like pain or stiffness, tend to get pulled toward whatever was most intense recently, so judging progress from memory alone often lands you at a conclusion that does not match the actual trend. Researchers call this recall bias, and pain research has been documenting it for decades.
Stone and colleagues at Stony Brook University in New York, publishing in Controlled Clinical Trials in 2002, compared paper diaries against electronic diaries and found that a substantial share of participants did not fill out their paper entries at the assigned times at all — they filled several days in at once, usually right before a clinic visit, and the reliability of those retrospective entries dropped sharply as a result. The study caught this because the electronic devices time-stamped every entry, exposing gaps that the paper group's participants had no way to hide. The takeaway carries over directly: a diary only does its job if you write in it at the moment, not a day later once memory has already smoothed over the details.
Which Scale Actually Holds Up: NRS vs. VAS
The two common ways to put a number on a subjective sensation like pain are the 0-10 Numeric Rating Scale (NRS) and the Visual Analog Scale (VAS), a mark placed along a 10cm line. Hjermstad and colleagues at the University of Oslo, in a systematic review published in the Journal of Pain and Symptom Management in 2011, compared the reliability and validity of several pain scales and concluded that the NRS is simple enough to use and reproducible enough to make it particularly well suited to self-tracking by non-clinicians. Several of the studies folded into that review found that comprehension and completion rates for the NRS were higher than for the VAS regardless of a respondent's age or education level — a meaningful point, since a scale that is confusing partway through a tracking period is a scale people quietly stop filling out correctly. The same logic applies to an NIR LED log: skip the elaborate questionnaire and just record a plain 0-10 number at the same time every day.
Why Recall Specifically Fails You Here
Part of the reason memory misleads you is not laziness, it is how memory for sensation works. When you try to summarize how your shoulder felt over the past week, you do not average every data point — you default to the most extreme moment and the most recent moment, a pattern psychologists sometimes describe with the peak-end idea. A single very good evening after a session, or one unusually stiff morning, ends up carrying disproportionate weight in your summary judgment, even though it was one data point among fourteen. A written log sidesteps this entirely because it does not ask you to summarize anything after the fact — it just accumulates the raw numbers so the averaging can happen later, deliberately, instead of automatically and inaccurately in your head.
Three Things a Diary Gives You That Memory Cannot
- A real trend line: you stop being thrown by daily ups and downs and can see the actual direction over two to four weeks.
- Controlled comparison: logging wavelength, duration, distance, and body area alongside how you felt lets you compare settings against each other instead of guessing.
- Protection from overreacting to one data point: an unusually good or unusually bad day stops getting more weight than it deserves.
Paper or Electronic — Does It Matter?
The Stone study also found that adherence to the actual recording schedule was much higher with electronic diaries than with paper ones. A note on your phone or a calendar reminder that prompts you to log immediately before and after a session beats a notebook you mean to fill in later. That said, the format is secondary — the thing that actually determines whether your data means anything is the habit of writing in the moment, not the tool you use to do it.
What to Record and How
What to Log, When, and How
Six Data Points Worth Recording Every Session
| Item | How to record it | When |
|---|---|---|
| Pre-session condition | NRS 0-10 | Right before the session |
| Area and wavelength used | Body area, 660nm / 850nm / combined | At the start of the session |
| Duration and distance | Minutes, centimeters | During the session |
| Immediate post-session feel | NRS 0-10, one-line note | Right after the session ends |
| Activity level that day | Normal / heavier than usual / lighter than usual | Before bed |
| Next-morning condition | NRS 0-10 | Right after waking |
A Four-Step Recording Routine
Step one, log your condition on a 0-10 scale right before the session. Step two, write down the wavelength, duration, and distance you used — for example, 850nm, 12 minutes, skin contact. Step three, log your condition again right after the session, with a one-line note on anything unusual. Step four, the next morning, note how you feel compared to the day before. Put those four steps into a single table and a full week fits on one sheet of paper.
How Often You Actually Need to Log
For the first two weeks, log daily — that is what establishes your baseline, and skipping days early on means you never really know what normal looked like before you started. Once the baseline is solid, dropping to three or four times a week is usually enough to keep tracking the trend without it feeling like a chore. Any week where you change wavelength, duration, or distance is an exception — go back to daily logging that week specifically, so you can isolate what the change actually did. Related routines are covered in the cirius muscle soreness doms use guide.
Deciding When to Move From Daily to a Few Times a Week
The signal to drop from daily to three or four times weekly is not a fixed number of days, it is what your first fourteen entries look like. If your morning scores over that stretch cluster within a point or two of each other on non-session days, and the pre/post-session gap on session days is reasonably consistent, you have a real baseline and daily logging from that point mostly adds noise rather than information. If the numbers are still swinging by three or four points day to day with no obvious pattern, keep logging daily for another week rather than dropping down — a baseline built on a volatile two weeks is not a baseline you can trust.
Signals to Pause and Reassess Rather Than Push Through
A few patterns in the log are worth treating as stop-and-check signals rather than just data points. If the skin at the treatment site develops persistent redness, warmth, or small blisters that show up in consecutive entries, stop sessions at that site and let it settle before resuming — do not simply note it and continue on schedule. If your two-week averages are trending worse rather than flat or improving after a full four-week block at consistent settings, that is a reason to change your approach rather than log through it for another month hoping it turns around on its own. And if a single day's entry includes a sharp, unfamiliar pain unlike your usual baseline discomfort, treat that as a reason to stop and evaluate rather than as one data point to average in.
Secondary Metrics Worth Adding
A 0-10 score by itself misses a lot of nuance. These secondary metrics, added alongside it, give you a far more complete picture than the feeling score alone.
- Sleep duration and quality: how many hours you slept and how many times you woke up helps you separate a bad morning score caused by poor sleep from one actually caused by your condition.
- Joint range of motion: for areas like the knee or shoulder where range of motion matters, a weekly measurement with a phone angle app gives you an objective number independent of how you feel that day.
- Photos: a weekly photo from the same angle under the same lighting captures changes in skin tone or swelling that are hard to describe in words but easy to compare later.
- Weather and barometric pressure: joints can be sensitive to pressure changes, so even a simple sunny/cloudy/rainy note can help explain a pattern later.
A Simple One-Line Format
A notes app or spreadsheet works fine if you repeat the same one-line format every day: date / area / wavelength / duration (min) / distance (cm) / pre-session score / post-session score / next-morning score / notes. Two months of entries in this format is enough that a spreadsheet's sort and filter functions alone let you compare conditions with almost no extra effort.
What a First Week Actually Looks Like
When you are just starting out, filling in something short like the example below is enough to get going — the entries do not need to be polished sentences, the important part is not skipping the same fields every day.
| Day | Area / wavelength | Pre | Post | Next morning | Note |
|---|---|---|---|---|---|
| Day 1 | Shoulder, 850nm 12 min | 6 | 5 | 6 | Kept 3cm distance |
| Day 2 | Shoulder, 850nm 12 min | 6 | 4 | 5 | Switched to skin contact |
| Day 3 | Shoulder, 850nm 12 min | 5 | 4 | 5 | Same setup as prior day |
| Day 7 | Shoulder, 850nm 12 min | 5 | 3 | 4 | Weekly average trending down |
Even one week of entries like this starts making the pre/post gap and the next-morning trend visible. Keep stacking weeks like this and by the end of a month you usually have a fairly clear answer about which session conditions actually work best for you.
Reading the Data You've Collected
Reading the Data Once It Piles Up
Average by the Fortnight, Not the Day
Daily scores swing around a lot because they are pulled by sleep, activity level, and stress on top of whatever the device is or is not doing. Instead of reacting to each day, average two weeks of scores and compare that average to the previous two-week average — it is a much steadier basis for judgment. If weeks one and two average 6.2 and weeks three and four average 5.1, that is a real direction. A single day dropping from 6 to 4 and bouncing back to 7 the next day is much more likely to be noise unrelated to the device.
Building a Comparison Table by Condition
- By wavelength: line up the average score for a week using only 660nm against a week using only 850nm on the same area.
- By time of day: compare next-morning condition after a morning session versus an evening session.
- By distance: note the difference in feel between skin contact and a 3cm gap during the session.
Timing Varies From Person to Person
Among users who have kept a diary for four weeks or longer, there is usually a gap of one to three weeks between when they first notice a temporary loosening feeling right after a session and when they notice their morning condition has settled into something reliably different. Knowing that gap exists ahead of time helps you avoid judging the whole thing off a few unremarkable early days. Background on the underlying light is covered in infrared vs near-infrared.
Turn It Into a Line Graph
A line graph makes a trend far more intuitive than a table full of numbers. Plot date on the horizontal axis and pre/post scores on the vertical axis in a spreadsheet, and the result generally settles into one of three patterns.
| Pattern | What it looks like | What it suggests |
|---|---|---|
| Gradual decline | Two-week average keeps dropping | Current protocol is often a good fit |
| Flat line | Day-to-day swings but no real change in average | Worth adjusting wavelength, duration, or distance |
| Irregular sawtooth | Large swings day to day | Outside variables like activity and sleep need controlling |
Cross-Checking Against Other Things You're Doing
Most people using an NIR LED device are also stretching, icing or heating, or adjusting how hard they train. If you note whatever else you did that day in a separate column, you may not be able to fully isolate the device's effect from everything else, but you can at least see which combination of activities tends to line up with your best stretches.
When the Numbers Stop Moving
Keep a log past four weeks and you will sometimes hit a stretch where the average simply stops moving. That is not automatically a bad sign — it can mean your condition has settled at a stable level. If the plateau persists, though, it is worth changing one variable at a time — wavelength, area, or time of day — and watching whether that brings the response back. Without a log, you would have no way to track what you actually changed or what happened afterward, which is exactly where the value of keeping one shows up again.
Applying This to an Actual Workday
If you sit at a desk most of the day, the useful comparison is usually a midday session against an end-of-day one — log your neck or shoulder score before lunch, use the device on a break, and check whether the afternoon slump you normally hit by 3pm shows up in your post-lunch entries the way it does on days you skip the session. Drivers dealing with low-back stiffness tend to get more out of comparing a pre-drive session against a post-drive one, since the relevant question is usually how you feel getting into the car in the morning, not how you feel at night. Parents running on broken sleep should expect their morning scores to be noisier than usual and should log hours slept alongside pain scores for a couple of weeks before drawing any conclusion, since a rough morning after a night with the baby up twice is not the same signal as a rough morning after a full night's sleep. Anyone who sleeps mostly on one side and treats a shoulder or hip should note sleep position in the diary too, since which side you land on can move the next-morning number independent of anything the device did.
Common Recording Mistakes and Cautions
Common Recording Mistakes
- Batch-writing entries: trying to recall several days at once bakes recall bias directly into the log and largely defeats the point of keeping one.
- Letting your anchor points drift: if 0 means completely comfortable on one day and slightly stiff on another, the scores are no longer comparable to each other. Write out, in a sentence, exactly what 0 and 10 mean to you when you start, and refer back to that same sentence every time you score yourself.
- Changing more than one variable at once: change wavelength, duration, and area all in the same week and there is no way to tell which change produced whatever difference you saw. Change exactly one condition at a time.
- Letting early enthusiasm inflate the numbers: right after buying a device, there is a natural tendency to score yourself more optimistically than the evidence supports. Logging objective measures alongside how you feel, like range of motion or photos, helps keep that in check.
- Not noting why you missed days: if you skip a few days, jot down why, even briefly — travel, a skin reaction, or just forgetting. It saves you from misreading the gap in your data later.
Making It an Actual Habit
A phone reminder set to your session time cuts down on missed entries considerably. Attaching the device itself to something you already do daily — right after your evening shower, or as part of getting ready for bed — tends to work better than trying to remember it as a standalone task. The first week or two can feel like a chore, but by the third week, most people find it has become a roughly one-minute habit rather than something they have to think about.
Safety Notes
Do not aim the device directly at the eyes. If you are taking a photosensitizing medication (tetracycline-class antibiotics, amiodarone, and similar drugs), or if you develop persistent redness or blistering at the treatment site, stop use and speak with a physician. Avoid direct application to the pregnant abdomen, over an active malignancy, or directly over the thyroid. An NIR LED device is a wellness tool meant to support everyday condition management, not a substitute for medical care — if pain persists or worsens, see a clinician regardless of what your diary shows. The diary itself can be a genuinely useful thing to bring to that appointment. Full safety guidance is covered in the LED safety precautions guide.
When to Stop Logging and See a Doctor Instead
A handful of patterns are worth treating as a reason to close the diary and get evaluated rather than as more data to collect. Pain that wakes you at night or is clearly worse lying down than moving around does not fit the usual musculoskeletal pattern and deserves a proper look. Unexplained weight loss alongside ongoing pain, a fever that shows up with the pain, or numbness, tingling, or weakness spreading down an arm or leg are all signals that go beyond what a home light therapy routine is meant to manage. So is pain that started after a clear injury and has been getting steadily worse across your two-week averages rather than holding flat or trending down despite consistent use. In any of these cases, the right move is to stop treating the diary as a wait-and-see tool and get an in-person evaluation — you can bring the log with you, since a clinician will often find the pattern of scores, timing, and triggers more useful than a description from memory.
