Which of the following is a sign of severe hypothermia?

Severe hypothermia occurs when the body's core temperature drops significantly, typically below 28°C (82°F). At this stage, the body's physiological responses change dramatically, leading to various signs and symptoms. One key indicator of severe hypothermia is the inability to walk or move effectively. As the body conserves heat and blood flow to extremities decreases, muscular coordination begins to fail. This loss of coordination is the result of both muscle and nerve function being impaired due to the low body temperature.

In contrast, excessive shivering typically indicates a milder form of hypothermia, where the body's mechanisms are still functioning to generate heat. A high heart rate is also more characteristic of mild to moderate hypothermia, as the body initially reacts to cold with increased heart rate and activity. Similarly, profuse sweating is not a sign of hypothermia but rather indicates that the body is still working to regulate temperature, which becomes less effective as hypothermia progresses. Thus, the inability to walk serves as a stark reminder of the severity of the condition and the critical need for immediate medical attention.