Controlled stress is a way to promote adaptation in the body, this may include, but it not limited to: training, fasting, cold immersions, breathing exercises.
One of the worlds prominent figures in the field is Wim Hof is a Dutch adventurer, known by the name “The Iceman”
He uses a method of controlled breathing, to help achieve a psychological condition called coherence. Which is said to lead to improved mental clarity, emotional stability and decision making.
Research on the Wim Hof Method suggest that people can learn to modulate their immune responses — a finding that has raised hopes for patients who have chronic inflammatory disorders such as rheumatoid arthritis and inflammatory bowel disease.
More to Explore
Kox, M., Eijk, L., ... Pickkers, P. (2014). Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. PNAS. (OPEN ACCESS)
Muzik, O., Reilly, K.T., Diwadkar, V.A. (2018). "Brain over body"-A study on the willful regulation of autonomic function during cold exposure. Neuroimage.