“Intervals” is one term for it, “threshold work” another. The recipe is simple: periodicity, intensity, and repetition broken by small periods of recovery. The process is not.
Intervals require the mind be taught to heel and be still despite its knowing the somatic stress to come. Emotional memory is no friend to muscle memory in this situation.
The kindness of athletes comes, I think, from understanding that we all suffer, whether fast or slow, and in our suffering we’re more alike than different. This gut-sense physiology
is our bounding box, our interface, our permeable gift to one another, and threshold work our furnace, lungs the tuyeres for the chemical and alchemical changes wrought.
It’s not unusual for speed work to produce fits of rage or tears. I’ve learned it isn’t from discomfort, however, just our sympathetic system on overload. But if we’re mindful
of the intervals, the thresholds we cross and re-cross, our bounding box becomes a bit looser, our legs faster, strides more like skimming, emotions and motion at last all in play.