A standard running file from Garmin Training Center - it does not show the Gaps since it is probably smoothed - the software does not provide a feature that can display the second-for-second Data:
The same Training File in WKO+ 3.0, which clearly show the gaps in the Data. this impacts both the calorie counting, TSS and IF. Due to the Gaps in HR for example, the Calories are always significantly lower than in for example Polar 800 or 725, or in a CompuTrainer.
And the Listing of Data that show the Gaps more visible:
Svømming i triathlon og tilbud om camp
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