Hills, hills, hills!!
There is a lot of literature out there on this subject and given everyone is different you need to find a plan that works for you. You are encouraged to assess your physical condition with your physician before beginning any training regime or entering our race. Cross-training is great preparation for attempting this event.
Here are a few links to some other training sites:
https://www.redbull.com/gb-en/5-best-hill-running-sessions
https://www.runnersworld.com/training/a20630818/hill-running-workouts-for-speed/
https://www.runnersworld.com/uk/training/motivation/a775792/10-best-hill-training-workouts/
