If you are a beginner scale:
30sec sprint- 10 sec rest
30 sec sprint- 20 sec rest
30sec sprint- 30 sec rest
Then go back down to 30sec sprint- 10sec rest!
If you are advanced:
1 min sprint- 10 sec rest
1 min sprint- 20 sec rest
1 min sprint- 30 sec rest
1 min sprint- 40 sec rest
1 min sprint- 50 sec rest
1 min sprint- 60 sec rest