When the body is sympathetically activated, blood vessels in the periphery constrict and blood shifts away from the hands and feet into other parts like the muscles of the arms. This shift in blood flow can be measured via the temperature of the hands and feet, indicating the peripheral temperature.
The higher the temperature value, the less constricted the vessels are, gradually indicating relaxation.
How is it measured?
Skin temperature measurement uses a sensitive thermistor, which is designed to monitor very minor temperature changes.