Tough mudders and extreme athletes are actually seeking out pain as a way of escaping the anxieties of modern life, according to scientists.
A research team decided to look at why pain-ridden events are increasing in popularity with people paying for the privilege.
They interviewed Tough Mudder participants to get to the bottom of why they do it.
The event involves about 25 military-style obstacles that participants must overcome in half a day.
Among others, its events entail running through torrents of mud, plunging into freezing water, and crawling through 10,000 volts of electric wires.
Injuries have included spinal damage, strokes, heart attacks, and even death.
The study, Selling Pain to the Saturated Self published in the Journal of Consumer Research, showed that one of the reasons was to offset the modern sedentary lifestyle.
One of the authors, Dr Rebecca Scott of Cardiff University, said: "How do we explain that on the one hand consumers spend billions of dollars every year on analgesics and opioids, while exhausting and painful experiences such as obstacle races and ultra-marathons are gaining in popularity?
"After speaking to Mudders, we learned that pain helps individuals deal with the reduced physicality of office life.
"Through sensory intensification, pain brings the body into sharp focus, allowing participants who spend much of their time sitting in front of computers to rediscover their corporeality.
"Electric shocks and exposure to icy waters might be painful, but they also allow participants to escape the demands and anxieties of modern life."
The study also concluded that events such as Tough Mudder also allows competitors to get a sense of fulfilling their lives.
She added: "By flooding the consciousness with gnawing unpleasantness, pain provides a temporary relief from the burdens of self-awareness.
"Leaving marks and wounds, painful experiences help us create the story of a fulfilled life spent exploring the limits of the body.
"The proliferation of videos recording painful experiences such as Tough Mudder happens at least partly because a fulfilled life also means exploring the body in its various possibilities.
"In a context of decreased physicality, market operators play a major role in selling pain to the saturated selves of knowl