Where does endurance collide?

In metaphysics, to endure is a theory of how a thing persists through time: an enduring object is wholly present at every moment of its existence, lacking temporal parts, so the same complete object exists now and later rather than being spread out as a sequence of time-slices. David Lewis's On the plurality of worlds drew the now-standard contrast between enduring and perduring, where a perduring thing persists by having a different temporal part at each time. The referent is a mode of persistence of objects, argued over the problem of temporary intrinsics and change, and it is a wholly different construct from an athlete's stamina or a metal's fatigue threshold despite the shared root of lasting through time.[1]

Unit

Not applicable: a mode of persistence, argued rather than measured

Recovery means

Not applicable

Measured by

Not measured; adjudicated by philosophical argument about change, temporary intrinsics, and identity over time

In materials science the endurance limit (or fatigue limit) is the stress amplitude below which certain metals, notably many steels, can in principle undergo an unlimited number of load cycles without failing by fatigue, appearing as a plateau in the stress-versus-cycles (S–N) curve. Suresh's Fatigue of materials sets out how cyclic loading nucleates and grows cracks and when a true limiting stress does or does not exist. The referent is a threshold stress for infinite cyclic life, measured in megapascals from fatigue testing, and it has nothing to do with human stamina or the metaphysics of persistence beyond the common idea of enduring repeated demand.[2]

Unit

The stress amplitude, in megapascals, below which fatigue failure does not occur

Recovery means

Not applicable

Measured by

Determined from S–N (Wöhler) curves in cyclic fatigue testing, as the stress asymptote for very high cycle counts

In exercise physiology, endurance is the capacity to sustain prolonged muscular effort, set by how much oxygen the body can take up and use, the fraction of that maximum a person can hold for a long time, and the economy with which they move. Joyner and Coyle's 2008 Endurance exercise performance: the physiology of champions integrates maximal oxygen uptake, lactate or ventilatory threshold, and movement economy into a single account of what limits sustained performance. The referent is physiological staying power under prolonged load, measured in oxygen uptake and time to exhaustion, a distinct construct from a metal's fatigue threshold or a philosopher's enduring object.[3]

Unit

The duration or distance of effort sustainable at a given intensity

Recovery means

Recovery restores the substrates and clears the fatigue that endurance work depletes, raising sustainable output over a training cycle

Measured by

Assessed by maximal oxygen uptake, lactate or ventilatory threshold, exercise economy, and time to exhaustion or time-trial performance