Hi,
I live and train in Finland, where running in the cold is a fact of life, rather than a choice (but some like it so…).
Almost every winter run starts the same way: the first minutes of heart rate are just wrong.
The watch shows 160–185 bpm on an easy jog, then the reading snaps back to something sensible.
It distorts the averages, the zone time and the load.
I got tired of fixing these by hand, so I built the tool I wanted for it. It’s part of The Split, a free web editor for FIT files that I already use for merging and cropping activities, which I announced earlier this year.
What it does
- You load a FIT file and it marks the stretches that look like spikes automatically
- Each one gets a confidence label.
- You can tick or untick each one, change the sensitivity
- If the automatic detector doesn’t see what you see as a spike you can switch to manual mode and select a range yourself, so the detector runs in that specific range.
- Repair replaces only the ticked stretches with a physiological model (rather than a straight lines or zeros) of how HR usually raises.
I wrote up what spikes look like, why they happen (cold, loose straps, and cadence lock, which is a separate cause) and how to tell them apart:
I’d really like feedback, especially files where it ticks the wrong thing or misses a spike. Those are the most useful cases for me.
Few screenshots here:
