Mechanisms of thermal treatments in trigger points of the skeletal muscle: Computational microstructural modeling

Abstract

Thermal treatment of trigger points in muscle fibers is easily applied without professional assistance and, thus, popular. In this work, we study the influence of thermotherapy and cryotherapy on trigger points in a fascicle by means of a microstructural model. Details about the mechanisms of different thermal treatments to relieve muscle pain in tensed muscle fibers are provided. We consider short-term as well as long-term temperature treatment. For the former, the electromyography activity in the trigger point is assumed to remain constant. This results in muscle pain relief after heating, as the compressive strains and compressive passive stresses in the trigger point are reduced, however, cooling causes the opposite behavior and enhances muscle tension. The different thermal expansion coefficients along the tensed muscle fiber provide maximum relaxation during heating, as the fiber regions next to the trigger point contribute to relaxation. Long-term treatment reduces the electromyography activity in the trigger point as in vivo muscles and electromyography activity reduction strongly effects the behavior along the entire tensed fiber, thus, pain relief in trigger points is not only obtained during heating but also during cooling.