High Quality Content by WIKIPEDIA articles! Long slow distance (LSD) is a form of aerobic endurance training in running and cycling. Physiological adaptations to LSD training include improved cardiovascular function, improved thermoregulatory function, improved mitochondrial energy production, increased oxidative capacity of skeletal muscle, and increased utilization of fat for fuel.Ernst van Aaken (1910–1984), a German physician, is generally recognized as the founder of the long slow distance method of endurance training.