It seems that the only way to force a VO2 calculation with the Vivosport is to walk or run outdoors with GPS
The Vivoamart 3 and 4 can apparently calculate VO2 without a GPS. This would allow walking or running on a treadmill, nice for winter months and good for walkers.
Clearly it would be easy to allow indoor walking or running to calculate VO2 max with the Vivosport. I like the Vivosport but it really is less capable or useful to indoor walkers and runners like myself than the less expensive Vivosmart series. Please add this feature.