When a muscle is either strongly contracted or over-stretched, there is a mechanical stress on the local musculature that slows the flow of blood into and out of the muscle.

low heart rate and low blood pressure can lead to ischemia; when these parameters return to normal, the re-perfusion of the blood into the vascular system can trigger inflammation that then adds to cellular injury.

Although inflammation speeds the healing of wounds and is antimicrobial, it also seems to be an important causative aspect of arthritis, asthma, atherosclerosis, etc. The inflammatory response is inhibited by cortisone.

Histamine dilates the blood vessels locally, so that the injured tissue is flooded with fresh blood, making the affected area both redden and rise in temperature.

Histamine acts not only to trigger the pain reaction, but also to promote inflammation, this being the first stage of healing following an injury.

Though women more often tend to catastrophize their pain than do men, these same men are less willing to admit to their pain, fearing that it would make them look weak. Women’s higher sensitivity to pain is in accord with their higher sensitivity to all manner of external sensations, painful or not, such as light levels, noise, odor, temperature, e

men have a stronger release of pain-easing endorphins than do women.

given a pain stimulus of constant intensity, women perceived the stimulus as more intense than did men and in doing so, showed more brain activity in pain regions of the brain than did men.

Women are decidedly more at risk for chronic pain conditions such as rheumatoid arthritis, lupus, and fibromyalgia, and women on average have a lower pain threshold (the point at which pain is first felt), and less pain tolerance (the time for which one can endure the pain) than does the average man.