In this insightful episode, hosts Andy and Cathy dive deep into the world of ultra-running, exploring the intricacies of key quality training sessions. Drawing from personal experiences and extensive reading, they demystify the often confusing terminologies and methodologies surrounding ultra-trail running training. The discussion begins with the concept of Fartlek, a playful and flexible speed training method that allows runners to experiment with different paces. Andy emphasizes the importance of understanding Fartlek as a non-prescriptive session, designed to ease athletes back into speed work while having fun. Next, they explore Threshold sessions, which are crucial for improving an athlete's endurance and speed. By breaking down the fastest pace a runner can sustain for 30 to 60 minutes into manageable intervals, Andy explains how these sessions can enhance an ultra-runner's overall performance. Tempo sessions are then introduced as a versatile tool for building endurance and preparing for longer races. These sessions, which are slightly less intense than threshold workouts, help runners practice pacing and fuel management, making them ideal for both beginners and advanced athletes. As the conversation progresses, the focus shifts to Speed sessions, which push athletes above their threshold pace. Andy and Cathy highlight the benefits of these sessions in improving running economy, efficiency, and injury resistance, while also acknowledging the potential risks for less experienced runners. Finally, the episode delves into VO2max sessions, examining their role in enhancing an athlete's maximum oxygen uptake and overall performance. While acknowledging the genetic factors that influence VO2max, the hosts provide guidance on who should incorporate these sessions into their training and when. Throughout the episode, Andy and Cathy provide practical examples, tips, and insights to help ultra-runners of all levels optimize their training and achieve their race goals. Whether you're a seasoned athlete or new to the world of ultra-trail running, this episode offers valuable knowledge to elevate your running journey.