8 key points from Training Essentials for Ultrarunning by Jason Koop which outline my current ultratrail running training strategy:
Structured training leads to better results than running more. There's generally too much focus on volume. Superlong runs are very hard on the body. The workouts necessary for best cardio fitness may seem simple and boring, but these methods will make you prepared for success. Extreme gimmicks may seem to work for a while before fading out.
The limiting factor isn't your physical capacity to run fast. You can develop specific parts of your physiology through increasingly focused specificity during the year. Start with the broadest aspects of training like aerobic endurance. Do the most event-specific things last.
Ultrarunning is a thinking sport. Your mind is your greatest weapon. Use it skilfully and wisely. You have to think your way through the challenges. You need to train your brain as much as your body.
As you get fitter, a bigger training stimulus is required. But you also need to rest. Running yourself into the ground won't improve your race. Recovery is an important part of training. Find the right balance between work and rest.
You can most dramatically improve your race during the ascents. Lactate threshold work yields the greatest improvements. Preparing for the climbing (and also descending) in your event is a high priority throughout your training.
Your training needs to be specific to the demands of the event you are training for. Cross training won't directly improve your ultrarunning. Hiking can be beneficial. Non-running activities may make you a better overall athlete, but you should not do them at the expense of your running.
7. Perceived exertion
Heart rate is not a good training tool. Your brain is the only training tool yet that can determine the correct intensity and workload by perceived exertion.
8. High-carbohydrate diet
Forget fat adaptation. High-carb diet will deliver energy quicker to working muscles, make you run faster, and help you go farther.