Question Activity Recognition stops receiving updates when phone goes to standby(screen off st

I am having some trouble with activity recognition. I have implemented it in an app and it works fine when the device's screen is on. I have a log entry in my Activity recognition intent service class and I can see when it gets an update.So, I know it is working fine when the screen is on.

But then after the phone is put to standby(the screen is turned off) it stops detecting the uses activity.

My question: Why does my app stop tracking the uses activity after the device goes to standby mode? And how do I make it not stop detecting the users activity?

Let me know if you need to see any of the code or if you need any more details on my app.