An efficient interval training. After almost 2 km to warm up, you will go through 6 loops of about 4 km. Each loop can be subdivided in 3 parts: uphill (0-0.6 km), flat (0.6-2.4 km), downhill (2.4-4 km). Try the following for each loop: Go full power in the uphill part, reaching your max HR at the end, continue pushing during the flat part (staying at about 90% of max HR), and take it easy during the downhill part (reaching about 60% of your max HR at the end).
See my other videos and playlists at videos by Gonvil