I've recently replaced my 920XT with a 735XT, and noticed that the VO2 Max estimates and Recovery Interval seem to give different results between the two watches. This is based on road cycling with a power meter. For very similar activities (duration, average and normalised power, average heart rate), the 735XT comes out ~2 lower on VO2 Max (e.g. 59 on 735XT v. 61 on 920XT), and a much wider difference (typically double) for the Recovery Interval (e.g. 30 hours on 735XT v 15 hours on 920XT)
Has anyone else noticed anything similar, or have any ideas what is different. I've not changed any personal settings. Some ideas that I'm thinking could cause it:
- Maybe the watch calculates my age initially, but doesn't update it (i.e. it keeps the age as at the time of first sync). I could imagine this could account for a small difference in VO2 max, but not the difference in Recovery Interval
- I'm using the 735XT for fitness tracking and wearing it continuously, but I didn't for the 920XT. Maybe this is feeding in extra data (most likely heart rate) that could affect the calculations
- Or maybe the watches use different algorithms