The effects of muscle tension on cerebral circulation in blood-phobic and non-phobic subjects.

This study aimed to assess whether (1) a muscle tensing procedure which has been found to be useful in the treatment of blood-phobic patients produces an increase in heart rate and cerebral blood flow and (2) whether this increase is greater than that produced by mental effort alone. Subjects were 17 volunteers with a history of fainting in response to blood-injury stimuli, (12 were phobic) and 8 volunteers with no fainting history. They were required to (a) rest, (b) do mental arithmetic, and (c) repeatedly tense and release their arm and leg muscles. It was found that Ss, heart rate and cerebral blood flow velocity were significantly greater during the muscle tensing procedure than during mental arithmetic or resting conditions. The increased cerebral blood flow produced by muscle tensing may enable blood phobic patients to prevent fainting during exposure treatment.