Heart Rate Variability improved during exercise?

"HRV is the physiological phenomenon of variation in the time interval between heartbeats. The longer the interval between each heart beat, the more appropriately your body responds to stressful situations." With this understanding, I have an app on my Galaxy Note 4 called S Health that can measure heart rate, SPO2 and stress. The app uses a sensor on the phone that can detect and measure your HRV, which is what it uses to measure your stress level. With all of that said, to measure your stress level the app directs you to relax for 5 minutes and sit still while it measures the heart rate variability to gage your stress level. If I am sitting still and following the directions the app returns a high stress level. I tested it while I was walking around, not pacing consistently but rather just keeping in motion, in general. When I do this the app returns a relatively low stress reading. A healthy reading. I was expecting it to return a higher stress level because now my heart is under more stress to keep my body in motion. Because it returns lower stress levels while in motion I want some opinions about what this means about my heart rate variability and health. I tested this multiple times and it kept returning the same results… Staying in motion my HRV was more stabilized and staying still it went back to higher stress. My general stats are I am mildly obese and mostly sedentary as I work a desk job and go to school, sitting at a desk most of the day.

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