Which physiological change is NOT commonly associated with REM sleep?

During REM (Rapid Eye Movement) sleep, several distinct physiological changes occur, including variable heart rate, irregular respiration, and increased brain activity. However, one of the hallmark characteristics of REM sleep is a state of muscle atonia, meaning that most skeletal muscles are essentially inactive or "paralyzed." This temporary paralysis prevents individuals from acting out their dreams, which are often vivid during this stage.

Continuous muscle activity would imply a sustained contraction of muscles, which does not occur during REM sleep due to this atonia. Therefore, the absence of continuous muscle activity is consistent with the typical physiological changes associated with REM sleep. Understanding this aspect of REM sleep is crucial for recognizing its unique characteristics and how it differs from other sleep stages.