Durability

Durability refers to the time course and magnitude of deterioration in an athlete’s physiological, mechanical, and performance-related characteristics during prolonged, predominantly submaximal exercise. It reflects how well an athlete can maintain their functional profile—such as heart-rate stability, metabolic thresholds, running economy, neuromuscular function, and subjective effort—over many minutes to hours of sustained work.

Durability is not simply the ability to sustain power or pace; it describes the resistance to progressive drift in key physiological variables (e.g., heart rate, VO₂, lactate, ventilation), the preservation of movement quality and coordination under fatigue, and the attenuation of late-exercise performance decline. In trail and ultra-endurance contexts, durability captures the athlete’s capacity to maintain efficiency and technical proficiency over long climbs, descents, and environmental conditions, as well as nutrition challenges, which gradually wear the body down.

Durability is related to, but distinct from, fatigue resistance.

• Fatigue resistance typically refers to the ability to maintain force or power during short, high-intensity or near-maximal bouts (neuromuscular fatigue domain).
• Durability applies to longer-duration, submaximal exercise and encompasses multi-system deterioration—cardiovascular, metabolic, neuromuscular, and biomechanical.

Because durability concerns how physiological traits behave under fatigue, it is increasingly recognized as a fourth dimension of endurance performance, alongside VO₂max, thresholds, and economy. It is trainable and influenced by factors such as endurance volume, high-intensity work, eccentric loading (e.g., downhill running), nutritional strategies, environmental stress, and prior exposure to fatigue.