Withings as an ankle monitor

My experience over the last few weeks suggests that the Withings watch counts about half of my steps. I think of it as a stride counter.

Both the watch and the Oura ring under-count steps when the steps are due to short bursts of activity (walking down the hall to get clothes out of the dryer after sitting reading for an hour). The ring over-counts steps in certain situations. For instance, it will not count all this typing as steps, but it will count weightlifting or yoga as steps; apparently it senses correctly the difference between sitting and motion. However, I got an epic 17,000+ step count on the ring recently, when I drove my car for 10 hours. The ring detected the physical work and mental focus involved in driving cross-country and translated that into steps. The watch counted 2,465 steps that day; it only counted walking to/from the car when I stopped at gas stations and rest stops. The ring was clearly over-estimating steps and it appears that the watch was under-estimating.

Judging from the variety of commentary on the web and the occasional reply from Withings, the watch is calibrated to count steps only when there is a large arm swing. To test that idea, I wore my watch on my ankle for a day.

I was planning to do some household chores that day, so I expected a lot of walking from one end of the house to the other, a situation for which neither the Oura ring nor the Withings watch is well suited. I expected to get low step counts from the ring and very low step counts from the watch. The day did not turn out quite that way. I had a mix of sitting at the computer and housework during the day followed by a 6 minute walk. After the walk, I put the watch on my wrist. In the evening I took a hike in the foothills.

The table below shows the data summary. This day was the first time I had ever seen the watch have a higher step count than the ring. That only occurred when the watch was worn on the ankle and I was walking around doing chores.

		Step	Counts
Time of Day	Watch worn on	Withings Watch	Oura Ring	Difference (W - O)
12:00 pm	Ankle	1,583	1,588	-5
3:30 pm	Ankle	2,740	2,303	437
4:00 pm	Ankle	3,553	3,071	482
5:30 pm	Ankle	3,704	3,493	211
7:00 pm	Wrist	10,301	11,657	-1,356
10:30 pm	Wrist	10,733	12,725	-1,992

These data confirm my experience over the last few weeks (see earlier posts from June 16, July 9, and August 2, 2019).

• During normal daytime activities, including outdoor walking, the Oura ring, despite being worn on the finger, is a pretty good step counter. 
• There are a few situations that cause the ring to over-estimate steps.
• When the Withings watch is worn on the ankle, it counts steps accurately.
• During normal daytime activities, when the Withings watch is worn on the wrist, it seriously under-counts steps.
• During an outdoor walk, when the Withings watch is worn on the wrist, and a sport session is manually started, it counts steps pretty well. However, it still under-counts whenever arm swing is not exaggerated.