After a comp day, I'll sometimes pull up my watch data out of habit and see a heart rate graph that barely moved. On paper, it reads like an easy day. It wasn't. It was one of the hardest sessions of the month, and the watch simply wasn't there for most of it.
That gap between what the data shows and what actually happened is worth talking about, because it's easy to let a graph override your own memory of how something felt.
Why the data goes missing
Rolling isn't like running or riding. The watch either comes off before you step on the mat, or it's on but buried under a gi sleeve, getting knocked around and losing its read on your wrist the entire time. Some competitions I've logged manually afterward with an estimated duration and effort, because there was simply no clean recording to pull from. Either way, the result is the same: a session that demanded a lot shows up in the data as a session that demanded very little, or nothing at all.
If I only trusted the numbers, every comp day would look like a rest day. That's obviously wrong, so the numbers can't be the only source of truth here.
No heart rate data isn't a training signal. It's a gap in the data, and those are two very different things.
What I actually go by instead
When the watch can't tell the story, I rely on the same things people trained for decades before wearables existed. A few honest questions after a session tend to say more than a graph ever could:
- How did I sleep the night after, and did I need more than usual?
- Was I still feeling it in my shoulders, neck or grip the next day?
- Did I want to move again the next morning, or did everything feel heavy?
- How many rounds or matches did I actually get through, regardless of what got logged?
None of that needs a device. It just needs paying attention, which is easy to stop doing once you get used to a number doing the noticing for you.
Where this actually matters
This isn't really about BJJ specifically, it's about what happens when you let a tool define your effort instead of describing it. The same mistake shows up anywhere the tracking has a blind spot: a swim session where the watch loses GPS, a gym session where you forgot to start the timer, a hike where the strap slipped all afternoon. In every case, the temptation is the same, treat the absence of data as evidence of an easy day. It's rarely that simple.
The fix isn't ignoring your data. It's remembering that data only describes what it managed to see, and a missing reading is a limitation of the recording, not a verdict on the session.
Want your own training data read with context, not just numbers?
The Garmin/Strava Analysis Prompt is built to ask about the week behind the numbers before it says anything about them, so a quiet-looking graph doesn't get mistaken for an easy week.
Try the Garmin/Strava Prompt