They can release a cytokine called Interlukin-4 which enhances FGF production. Overtraining suppresses immune function, which will have negative effects on everthing mentioned here. Neurotrophins are substances produced in the central and periferal nervous system. In relation to the recovery process, neurotrophins control the function of macrophages and act as growth factors and stimulators of the production of antioxidants in nerve fibers. Immune cells have receptors along their membranes for cortisol, as well as for adrenalin and other stimulants.
Stress also decreases the release of neurotrophins, which can impair macrophage function.
Autogenic relaxation and meditation have positive, short term cortisol reducing effects. Autogenics used following a workout reduces cortisol levels leading to favorable effects on adaptations to training. The mechanisms of workout recovery can be powerfully addressed through massage. Post-workout relaxation causes a decrease in the stress hormone, cortisol. Cortisol can downregulate immune cell number and activity.