During which sleep stage does the majority of vigorous muscle activity occur?

The majority of vigorous muscle activity occurs during REM sleep. This stage of sleep is characterized by rapid eye movements and vivid dreaming, which is often accompanied by increased brain activity that resembles wakefulness. Despite the occurrence of intense dreams and brain activity, the body experiences a temporary paralysis of most skeletal muscles, known as REM atonia. However, certain muscle activities, particularly those associated with respiratory and eye movements, can be vigorous during this phase. Additionally, REM sleep plays a crucial role in memory consolidation and emotional processing, highlighting its importance in overall sleep health. Understanding the dynamics of REM sleep helps clarify why it is the time when significant muscle activity can occur, even if it is limited in scope to specific muscle groups.