When at rest, a healthy heart beat speeds up as you inhale, and slows down as you exhale. These moment-to-moment changes between successive heart beats are a telling measurement of nervous system health in terms of physical, emotional, and mental function. Studies show high heart rate variability is associated with better recovery following exertion, higher resilience to psychophysiological disorders, as well as positive feelings and outlooks on life. Stress, especially when prolonged, decreases heart rate variability. Training to increase heart rate variability by following slow, relaxed paced breathing decreases the effects of stress on the nervous system, leading to diminished negative psychophysiological issues.

Emotional arousal affects the pores on the surface of our skin, which in turn affects the subtle changes in sweating. The measure of conductance across the skin’s surface is a telling biometric for our mental engagement and perception of stress.

Cold hands are not simply due to winter weather, but an indication of the body’s response to anxiety and elevated stress. As a response to the pressure of a stressful moment, the body shunts blood flow away from the finger. The logic behind this is that the blood will be needed in more essential systems related to the fight-or-flight response. Repeated and sustained stress can lead the body to maintain the fight-or-flight state, keeping heat-rich blood away from the hands and thereby lowering finger temperature. When the body finally engages the relaxation response, blood flow is allowed to return to the peripheral parts of the hands, results in the warming up of the fingers.