Introduction

Abstract

The introduction presents the terms and concepts that underlie the chapters that follow. Many complex and unique terms have arisen in the field of muscle pain; they must be clearly understood when studying this phenomenon. For example, there is a difference between nociception, the activation of the neural matrix that responds specifically to noxious stimuli, and the sensation of pain that is subjective and of chronic pain in particular that evokes an affective and emotional response reflected in activation of specific areas of the brain. The terms associated with nociception are defined, and the mechanisms of transduction and transmission of nociceptive impulses through the nervous system cranially to activate the cortex resulting in the perception of pain are introduced. The differences between acute and chronic pain, and the unique features of muscle pain in contrast to cutaneous pain, are addressed in the introduction. Peripheral and central sensitization is of great importance in the transition from acute to chronic pain. The principles that underlie sensistization that results in increased intensity of pain, and in the spread of pain sensation spatially and temporally, summarized in the term referred pain, are introduced in this section. Muscle pain is associated with muscle hardness (specifically in myofascial pain syndrome) that is associated with muscle hardness. Muscle contracture, muscle spasm, cramp and stiffness are differentiated in the introduction. The mechanisms that underlie contracture, important in such conditions as myofascial pain syndrome, are explained. Finally, it is recognized that nociception does not simply follow a direct ascending path from peripheral stimulation to activation of the dorsal horn neuron and then thalamic and cortical neurons. The introduction lays the groundwork for the later discussion in the text of descending pain modulation mechanisms that are essential to understanding the sensation that we finally call pain.