I have a ? regarding the text files in logs on the VivoactiveHR for when you use system.println to save data there.
I know that it will allow 2 text files of 5 kb each, but what happens when the 2 files are filled ?
You have a 5k log file, and when that fills, it's copied as a backup, and the new file starts clean. If it fills again, it over-writes the backup and starts clean again. So the most you can have in the two files is 5k to about 10k.
Using Sys.printXX is an expensive op (time, etc) on a real watch and is really just a debug tool to be used sparingly...
Have you considered using the FitContibuter stuff? Start recording and with the data is in the .fit, users can see it as a graph on GC and not have to deal with a the .txt log file?