I understand that’s there are some differences between the two app on the vo2max calcultation. My question is on what app should i use when there is mix between a 5km segment trail run and a second part 5km of road for exemple. I always use run app but maybe I’m wrong ?
On an uneven trail surface your body works harder to keep you balanced and stabilized, and working harder = higher heart rate. As the VO2Max algorithm compares your heart rate to your pace, on a rough trail surface, your VO2Max estimate is likely to be off. Just running on a smooth gravel or dirt surface is unlikely to be a problem, but when rocks, roots or a tilted surface are involved, measured performance is likely to drop.
The Trail Run app does not calculate VO2Max, so it means your VO2Max estimates will not be distorted by rough surfaces.
I guess it depends on how rough you think your trail segment is.