Physiology
Fuel Easy, Fuel Hard
Learn how to match fueling to the workout: enough carbohydrate for hard and long sessions, enough total energy for recovery, and enough restraint to keep easy training easy.
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Explore how the body's systems support endurance performance. This category covers energy pathways, cardiovascular and muscular adaptations, recovery, nutrition timing, hydration, and how physiology informs pacing and zone training for ultrarunning, foundational endurance work, and advanced sessions.
Physiology
Learn how to match fueling to the workout: enough carbohydrate for hard and long sessions, enough total energy for recovery, and enough restraint to keep easy training easy.
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Physiology
A practical endurance guide to carbohydrate, glycogen, long workouts, gut training, recovery, and when to fuel more aggressively without turning every easy session into a race.
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Physiology
Learn how running economy works, why heavy strength training can improve it, and how to use relaxed strides without turning every easy run into a hard workout.
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Physiology
Running economy is the energy cost of running at a given pace. This research-grade guide explains how it is measured, why it predicts performance, what changes it, and how runners can improve it.
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Physiology
Lactate threshold is the intensity where lactate begins to accumulate faster than your body can keep it stable. Learn what it means, how it is tested, and how to use it in training.
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A privacy-first training log for iOS and Android. Free to start. Yours to make personal.
Physiology
Heart rate drift is the gradual rise in heart rate during a steady endurance session. Learn what causes it, how to measure it, and how to use it without overreacting.
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Physiology
A deep dive into the three physiological levers behind endurance performance: how much oxygen you can use, how much of that capacity you can sustain, and how efficiently you turn it into speed or power.
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