Figure 4.

Effects of physical exercise on the nervous system and pathological pain. Various functions of the nervous system are also affected by physical exercise. Thus, physical exercise enhances synaptic plasticity, regulates food intake, modulates circadian rhythm, enhances learning and memory processes, and modifies neural circuits (e.g., basal ganglia) that improve the functional mobility of subjects. It should be noted that with physical exercise, the continued contraction of skeletal muscle fibers produces a significant release of myokines by this tissue. These myokines, together with other diffusible factors secreted by glial and vascular elements of the nervous system, are responsible for the changes described with physical exercise. On the other hand, physical exercise also has an impact on pathological pain. In animal models, physical exercise has been shown to reduce thermal hyperalgesia and mechanical allodynia. This analgesic effect of physical exercise is mediated by less activation of glial cells (e.g., microglia), which secrete fewer inflammatory cytokines, and with this there is less sensitization and excitation of the nociceptive neurons of the dorsal horn of the spinal cord, but also from nociceptive neurons from other supraspinal pain processing centers. At the spinal level, physical exercise also produces less branching of nociceptive peptidergic (CGRP-positive) and non-peptidergic (IB4-positive) afferent fibers in the dorsal horn of the spinal cord; therefore, there is less input of pain. For details, see the main text. Source for figure illustrations: https://scidraw.io/ (accessed on 8 September 2021).