What is common about muscle contractions in Periodic Limb Movements?

Periodic Limb Movements are characterized by involuntary muscle contractions, typically affecting the limbs, that occur primarily during sleep rather than during wakefulness. These movements are often confirmed through the use of electromyograms, which are tools that measure the electrical activity of muscles. During sleep studies, these tests can detect the characteristic limb movements and help establish the diagnosis of this condition.

The national sleep objectives and diagnostic criteria emphasize the importance of these observations during sleep, particularly because they are often not noticed by the individual experiencing them, making sleep studies crucial for accurate diagnosis. By showing the muscle activity during sleep, electromyograms provide definitive evidence of the presence of Periodic Limb Movements, thereby supporting the diagnosis and understanding of the disorder.

The other options do not align with the defining characteristics of Periodic Limb Movements. For instance, while these movements can sometimes be associated with awakenings, their confirmation via sleep studies is the most definitive and clinically relevant aspect of the disorder.