This main set is a cross-country focused workout designed to have two impacts on the runner (for a track/road variant see this workout).
Firstly its a psychological training exercise, after having pushed hard for tens of seconds and got to the point where your lactic energy system has kicked in, your heart is beating hard and you are starting to want to gasp for breath then your natural instinct when the need to go hard ends, e.g. after the race has hit the first corner or at the top of an uphill kick, is to slow down a lot. This workout will help you learn to fight that, perfectly natural, instinct.
Secondly, your body will respond to large amounts of lactic acid as a training stimulus and by maintaining pace after a hard start your body will improve its ability to ‘lactate shuttle‘.
As with all my main sets this should be coupled with a high quality warm-up.
To set-up; find a large grass area where you can lay out a course that is around 1km long, put a cone or use an existing landmark at somewhere between 200 and 400m. If you set the course up appropriately then you can make the cone/landmark a ‘tight turn’ and practice that skill too.
The workout consists of running to the first marker at MAX EFFORT and then finishing the course at 2-3 seconds per km faster than 10km race pace. Have a standing or walking recovery until breathing normally again. Do 3-6 reps depending on available time.