On some devices you may need to edit some settings to avoid trainings getting interrupted. Se below for a guide on how to allow the app to keep running in the background during your whole training
MIUI 10
To let your app run successfully in the background, make sure your settings look like the following (here for example is Sleep as Android):
Power management
Please enable:
Settings > Advanced Settings > Battery manager > Power plan is set to Performance
Device Settings > Advanced Settings > Battery Manager > Protected apps – your app needs to be Protected
Device Settings > Apps > your app > Battery > Power-intensive prompt and Keep running after screen off
When you open recent apps tray, drag your app downwards – it will be locked. So even if you clear recent apps it will not clear from the background. Drag downwards again to clear your app from the background.