Ekman, Levenson, and Friesen (1983)

Chapter 1 endnote 21 & 23, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

[note 21] While face-posing, subjects could use a mirror and were coached by Ekman himself to move particular facial muscles.

[note 23] The 1983 study did, in fact, observe bodily changes as people posed the required facial configurations. This is a remarkable finding: just posing a particular facial configuration changed the test subjects’ peripheral nervous system activity, even while they were comfortably motionless in a chair. Their fingertips were warmer when posing a scowl (anger pose). Their heartbeats were faster when posing scowls, wide-eyed startle (fear pose), and pouts (sad pose) when compared to the poses for happiness, surprise, and disgust.

The classic 1983 study by Ekman and colleagues included 16 participants: 12 professional actors, and four scientists who study the face. The study evoked emotion in two ways:

1. By directing test subjects, muscle by muscle, to make and hold facial stereotypes from the basic emotion method for 10 seconds each (as described in How Emotions are Made); and,
2. By having test subjects "relive" (i.e., remember) past experiences involving each emotion category for 30 seconds each. For example, for sadness, test subjects might have recalled a loved one who passed away; for anger, they might have recalled an insult.

During both tasks, the subjects' facial movements were recorded on videotape, and their physiological measurements were taken — left and right hand temperature (measured on the palmar surface of middle fingers), heart rate, skin conductance, and forearm tension. Only 55.8% of the relived emotion data were used; the other recollections were either not intense enough, or other emotions were also experienced with similar intensity.

Ekman and colleagues describe their findings: "This experiment provides the first evidence (to our knowledge) of autonomic differences among four negative emotions... as well as showing general distinctions between positive and negative emotions in both tasks." Heart rate increased during anger, fear, and sadness (as compared to happiness, surprise, and disgust).  Finger temperature change was largest in anger and significantly greater than during fear, sadness, happiness, surprise and disgust.  A temperature change like this would occur when blood vessels dilate so that it is easy to move your arms and legs.  This will happen any time a person feels challenged (in a demanding situation that you feel you can cope with), even when you are not angry.