something i just discovered. if your activity was improperly recorded (sensor failure, HR signal loss) and you want to edit it on the connect - it won't change your training load... say it other way - if you enter activity on garmin connect it wont sync back to the watch and will not change your training load. basically to get proper estimate of your load you have to have perfect record of EVERY activity on your watch... called support - they said no workaround it as of now... ANYONE may be knows way around it? one of the reasons i've got this watch for coaching features which seem not easy to edit/repair if your recording was not perfect. polar had this very simple - you add whatever you want on personal trainer site and it adds to your activity load graph....
Training load is calculated on the watch - I think it is part of the licensing deal with Firstbeat (although I have heard rumors of better integration between watches and the Edge series coming in Q1 2018), so 2 way transfers may be possible in the future. But in the meantime any edits you do to the file (presumably using a PC?) won't be reflected in the watch analysis of Training Status.
You could perhaps use Training Peaks, which looks at load and Training Stress Score, but allows edits and uploads of activities.
That said, I think training load is driven by HR measurements only. Sensor failure of power meters and the like shouldn't affect it. They're not immune to failure, but connections with HRM's tend to be more stable than some other sensor types. Short dropouts of an HRM won't materially affect training load calculations, and even missing 30 minutes of data from a single training session due to a dead sensor battery won't make a huge difference to weekly training load. But missing 30 minutes of EVERY session will.
