Which of the following is NOT a cause of acute pain?

Acute pain is typically characterized by a sudden onset and often results from a specific injury, illness, or event. Trauma refers to physical injuries such as fractures or cuts, which can lead to acute pain. Childbirth is another clear example, as it involves intense and immediate pain often associated with the physical process of labor. Severe medical illness, such as appendicitis or a heart attack, can also present acute pain due to the rapid onset of symptoms associated with these conditions.

On the other hand, lack of physical activity is generally not a direct cause of acute pain. Instead, a sedentary lifestyle might lead to chronic pain conditions over time, such as muscle stiffness or degenerative changes, rather than acute instances of pain. Therefore, it does not fit the typical profile of causes associated with acute pain.