What primary indicator signals the progression from mild to moderate hypothermia?

The primary indicator that signals the progression from mild to moderate hypothermia is the cessation of shivering. Shivering is the body's natural response to cold, functioning as a metabolic mechanism to generate heat and maintain body temperature. As the body temperature continues to drop and hypothermia worsens, the body's ability to generate heat through shivering diminishes, leading to its cessation.

This loss of shivering indicates a significant level of hypothermia as the body's protective mechanisms fail, suggesting that urgent intervention is necessary to prevent further decline in temperature and potential complications. The absence of shivering in moderate hypothermia is a critical sign to first responders and rescuers, highlighting the need for immediate warming measures and medical attention.

The other options do not accurately reflect the physical responses associated with the progression of hypothermia. Rapid heart rate is typically seen in the initial stages of cold exposure, increased sweating is counterproductive to hypothermia, and improved coordination usually occurs as a result of warming rather than a signal of progressing hypothermic conditions.