No one recommends quitting apps on the iPhone. Backgrounds apps are suspended. If you don't want an app to run in the background, you can turn off "background app refresh" in the settings for specific apps.When you run an app on an iPhone it runs and you need to have it running in the background in order for it to collect data.
ie you can not quit the app or else no data will be collected.
I always quit un-needed apps on my iPhone and do not leave apps running in the background.