Long slow distance

Long slow distance (LSD) is a form of aerobic endurance training used in sports including running,^[1] rowing,^[2] skiing ^[3] and cycling.^[4][5] It is also known as aerobic endurance training, base training and Zone 2 training.^[6] 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.^[4] Ernst van Aaken, a German physician and coach, is generally recognized as the founder of the LSD method of endurance training.^[7][8][9]

LSD training is a form of continuous training performed at a constant pace at low to moderate intensity over an extended distance or duration.^[10] The moderate training intensity of LSD is effective in improving endurance and maximum oxygen uptake in individuals who are undertrained or moderately trained.^[10] Although LSD training is not effective when used in isolation by well-trained athletes,^[10] there is substantial evidence that elite athletes spend 70% or more of their training time at LSD output levels, that LSD effort levels are a necessary part of the training of world class athletes,^[11] and that LSD workouts are primary drivers of the lower resting heart rates seen in well conditioned athletes.^[12]