Next to offering proper body support in order to allow musculoskeletal recovery, the sleep system should also provide adequate conditions to initiate and maintain sleep. Little is known about the exact mechanisms through which sleep systems
affect sleep. As mentioned before, posture changes and body movements are necessary to prevent overloading of soft tissue. Consequently, normal sleep is characterized by the presence of 20 - 40 posture changes per night [44, 37].
Although necessary, too much movement during sleep may reduce sleep quality,since it is associated with arousals and sleep fragmentation