If you've never heard of it here's a video https://www.youtube.com/watch?v=TM3_TMEc-qw&ab_channel=RedBull.
The race is 400m long and around 100/200 meters of elevation depending on the course, the steepness reaches something like 78%, the winners time is around 3-5 minutes
How would you train for a race like this? What could be some key sessions? How important would be training in the gym, have strong calves...