Ultramarathon running is a complex sport. Jason Koop's updated book, "Training Essentials for Ultrarunning," dives into the complexity to help answer many of the questions that ultrarunners and other competitors face as endurance athletes. The book is filled with evidence-based methodologies that may be useful for athletes in other endurance sports beyond ultrarunning.

Koop is a leading authority and one of the most sought-after coaches in trail and ultrarunning. He has over 20 years of coaching experience and is the head coach at CTS Ultrarunning. He's an ultrarunner in his own right, having completed a 250-mile race recently and is preparing for Hardrock 100 this summer.

Athletes looking for training guidance for ultra-distance sports beyond ultrarunning may find the evidence-based methodologies useful for their training. Koop self-published the book and hosts a podcast, Koopcast, centered on ultrarunning performance. You can find more information about him and his book at jasonkoop.com.