Sleep cycle compression

Cycle compression (often just called compression) refers to the change in cycle length. LS-compression (confusingly also often just called compression) refers to the reduction of light sleep with no change in cycle length.

Sleep cycle compression is the process by which core cycles change in length, sacrificing light-sleep (or % of it) in the process. This is one of the two processes underlying adaptation, along with repartitioning.

By default, a sleep cycle is usually 90 minutes long and contains 50-60% light sleep. On a reducing schedule, two things can happen: Cycles can contain more vitals through SO-vitals and reduction of transitional light-sleep, and cycles can decrease in length such that light sleep is also reduced. The replacement of LS with vitals is called ls-compression, the reduction in length is known as cycle compression. The opposite, where sleep cycles lengthen, is also a part of the term, and can also allow for more vitals per cycle as transitional light sleep is not lengthened.

Cycle compression is seen mostly in DualCore schedules, where cycles are lengthened in DC0 (~105m) and DC1 (~100m), and compressed in DC2 (80m), though many non-DC schedules also compress cycles to about 80 minutes.