“It gives people the freedom to enjoy their workout without the pressure of having to hit certain splits or distances,” says Moses.
It also helps you keep your heart rate elevated throughout a session, enabling you to build endurance while hitting speeds that are usually higher than your threshold pace. “You get multiple benefits from the same session,” says Moses.
It is also an effective way of judging your pacing better and learning how to speed up and when to slow down, particularly for longer runs on trails with variable terrain.
“Inexperienced runners will often go out too fast on Fartlek sessions and then they struggle to finish the session or they slow down or walk. It trains you to manage your pace better—slow down in the first half so you can finish strong—and get into good habits so you are more likely to execute a better race plan,” says Moses.