Chris Hemsworth survived a firefighting drill and a Navy SEAL-style drowning test using 3 stress management tools in ‘Limitless’ series

• Chris Hemsworth took on extreme challenges for the new series "Limitless" in search of longevity.
• His tasks included a Navy SEAL style drowning test, firefighting, and crossing a 900-foot high crane.

Chris Hemsworth tries not to drown, throws himself into a raging inferno, and conquers his fear of heights to cross a ledge 900 feet above the ground — all in an effort to reduce his stress.

That's just the first episode of the National Geographic series "Limitless," premiering November 16 on Disney+.

The show follows the actor, known for playing Thor on the big screen, as he takes on real-life superhero challenges to test how extremes of human experience might lead to a longer, healthier life.

Too much stress can be deadly, according to Modupe Akinola, a social psychologist at Columbia Business School who worked with Hemsworth for the show.

Prolonged periods of stress can lead to higher risk of illnesses like cancer, heart disease, and diabetes, in part because of high amounts of a hormone called cortisol, research suggests.

The idea is that by facing down extreme situations, Hemsworth will be better able to manage more typical stresses, such as taking care of his kids, juggling a tough work schedule, or worrying about the success of his latest film.

"This isn't about the feat of it, this is about preparing you to be able to manage and be present with the emotions you're feeling right now," Akinola said in the episode. "It's kind of like training your mindset to be okay and embrace the stress so that it doesn't kill us later."

But you don't necessarily have to risk your life to keep your stress under control.

Hemsworth learned three simple strategies, all of which you can do with no special equipment, training, or daredevil stunts required.

Positive self-talk may reduce anxiety and boost performance

As part of the training, Hemsworth takes on a Special Forces "drown-proofing" drill, performing underwater somersaults and other tasks with his hands and feet bound.

After failing initially, Hemsworth learns to control the panic and complete the drills by shutting out negative thoughts, and reminding himself he is capable of completing the task.

"It's like my stress is no longer holder me back," Hemsworth said in the episode.

The simple act of mental cheerleading can induce a physiological response of improved blood flow and breath control, leading to better athletic performance and mental and physical health, according to the Mayo Clinic.

'Box breathing' can calm your mind and body in high-pressure situations

Another tool Hemsworth learns, called "box breathing," helps him stave off panic during a strenuous firefighter exercise.

To perform box breathing, inhale for four seconds, hold for four seconds, exhale for four seconds, and pause four seconds, imaging each action as tracing a box shape.

The process induces calm by disrupting the body's natural flight-or-flight response of rapid breathing, which can exacerbate the mental sensation of fear, further ramping up the physical response and creating a vicious cycle that can lead to panic.

Breaking up a scary task into smaller segments helps you stay focused

For the episode finale, Hemsworth has to make his way across a crane atop a 900-foot high building, which he tackles a step at a time.

The strategy of segmentation can prevent your mind from being overwhelmed by the totality of a difficult or risky goal by separating it into small tasks, according to professional slackliner Faith Dickey, who has set world records for crossing massive heights and distances on a narrow rope.

"Sometimes all I need is that small bit of positive thinking that I can take one step," she said. "I walk through fear. I don't try to make it go away."