The Science Behind Adrenaline, Your Survival Secret Weapon

Adrenaline can be a life-saver. But how does it work?

Photo: Jordan Siemens/Stone via Getty Images

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As much as you can prepare for the worst case scenario in the backcountry with gear, training, and mindset, you can’t know how your body will react until something actually goes wrong—like when Mariella Colvin and Will Toor set out for what they thought would be a moderate day of mountaineering in Rocky Mountain National Park this summer. 

The experienced husband-and-wife mountaineers were approaching the top of a couloir when they suddenly found themselves tumbling 900 feet down the snow. Once they came to a stop, Will, who had broken his femur, experienced a bout of shock and confusion while Mariella, who did a quick assessment of her body and determined she was mobile, quickly sprung to action. Unaware of the extent of her internal injuries, she started walking in search of help.

In this scenario, and many others like it, we see someone’s fierce willpower to survive entirely override and delay pain. Mariella had nine broken ribs, three fractured vertebrae, a broken wrist, and a broken sternum, but she hardly noticed her injuries at the time. This prolonged delay of physical suffering—enough for Mariella to enjoy the scenery and walk more than a mile off-trail to a campground—is a textbook example of adrenaline’s importance when we find ourselves in life-or-death scenarios. Time and time again, we hear about adrenaline as a “fight or flight” response, or an addictive feeling for people who identify as “adrenaline junkies.” 

To better understand adrenaline, we asked a few experts about how it works, how it can save us, and ultimately, why it shows up in so many stories we cover at Backpacker.

What is adrenaline?

Medically speaking, adrenaline isn’t a single hormone, but the colloquial name for a series of hormones like epinephrine and norepinephrine released from the adrenal gland, says Dr. Elena Christofides, an endocrinologist who specializes in diabetes, hypertension, thyroid disorders, and more. The adrenal gland produces critical hormones as a part of the sympathetic nervous system, a global neurologic part of the body that helps you regulate things like heart rate, blood pressure, digestion, and sweating. 

Adrenaline is triggered when the amygdala—a part of the brain that processes fearful and stressful stimuli—senses danger and communicates with the hypothalamus, a region in your forebrain that controls homeostasis. As part of our “fight or flight” system, cortisol is the “fight” hormone, allowing us to store more energy, whereas adrenaline is the “flight” hormone. 

Scenarios that can trigger adrenaline while backpacking range from minor stressors like running out of daylight for setting up your tent to the more extreme like falling down a couloir. 

“It isn’t about actual stress, but perceived stress,” Christofides says. “It is simply a marker that shows up when your body needs to be in prime action mode.”

How adrenaline can save us

When adrenaline floods our system from our nerve endings, our body’s response is physically apparent, says Christofides. First, our heart rate increases to improve the oxygenation of our tissue. Our blood vessels shrink and contract in our upper body, digestive system, and genitals to preserve blood for our bigger muscles. Blood rushes to our heart, lungs, shoulders, glutes, and back—muscle groups that help us flee danger. 

Our pupils also constrict to focus our attention directly in front of us, and blood flows to the central part of our brain responsible for integrating environmental clues that might help us flee or act. Fine motor skills become difficult, and rational thought goes out the window.

Adrenaline also unlocks some “superhuman” qualities, Christofides says. The great burst of energy can boost speed, strength, and endurance. It can also increase tolerance for pain, or suppress it entirely.

Christofides says both adrenaline and cortisol were likely at play for Toor and Colvin. “He had a fight, she had a flight,” she says, adding that testosterone is another adrenal hormone often coupled with cortisol. Given Will’s fractured femur, his body froze in place to prevent further injury. But because Mariella was still mobile, she was able to seek help.

Adrenaline’s prominence in adventure stories

In narratives about outdoor adventure, adrenaline is often linked to risk, especially when the term “adrenaline junkie” comes up. We each have a different risk threshold and similarly, we each perceive stress differently.

Kristin Jacobson, a professor of American Literature at Stockton University in New Jersey, has studied adrenaline’s cultural implications, which she details in her 2020 book The American Adrenaline Narrative. In her research, she discovered two trends among athletes and authors in terms of adrenaline. Some really embraced the idea of chasing an adrenaline rush, while others rejected the term and preferred controlling the risk. “Why do people enjoy taking that risk?” she says. “It’s not to fail usually, but it’s that feeling of accomplishment.” That, in turn, can feed our production of dopamine and adrenaline.

At the same time, even individuals who prefer to control risks may not be assessing them properly. Jacobson fears that adventurers aren’t considering the worsening climate crisis as an additional risk factor in their decisions. Nature today is a lot more unpredictable than it was in decades past. And in the end, even the biggest adrenaline rush can only do so much to help keep us alive.

From 2022