The session is an Under/Over format - work a little easier on the way out, turn on the whistle and a little harder on the way back to make the turn again at the other end.

SET 1: @9m40s 

4 x (1min 15s out RPE 7-7.5 + 1m 10secs back RPE 7.5 -8) - continuous run

2mins easy recovery 

SET 2 : 13m 20s

4 x (1m 45s secs out RPE 7- 7.5 + 1m 35s secs backRPE 7.5-8) - continuous run 

2mins easy recovery 

SET 3:  @7m 40s

4 x (1min out RPE 7-7.5 + 55secs back RPE 7.5 -8) - continuous run