Is there a way to let the screen lock and have the lap timer run in the background?

I've been using Lap timer for years and finally need to fix this. I am using an Iphone 5 with OS 10.3.3. My screen lock is set a two minutes. The timer stops working if the screen locks or I get a call,text or any type of notification. To use it I have to set screen lock at never and hope no one cal...