We managed to get in touch with the moderators of r/SweatyPalms and they were kind enough to have a little chat with us about the subreddit. 

"We actually don't have to do much policing," the team told Bored Panda. "Like any sub on Reddit, we get spam and repost bots. We guard against those, but that's mostly it."

The moderators said that the members are fairly active, and the posts receive a fair number of comments, too. "We generally get a good representation of Redditors who appreciate a jolt of fear and a good, old-fashioned adrenaline rush."

"The pics that garner the most attention on our sub are the ones that involve everyday people in pretty extreme situations. I think those are the ones that resonate with members the most because it really doesn't take much imagination to see yourself in those (very) terrifying scenarios!" they added.

According to Nathalia Gjersoe, who is a senior lecturer in developmental psychology at the University of Bath, there are various reasons why our body responds like this in the absence of any real threat.

For instance, do you wince when someone is punched in a movie or squirm when someone is shamed or humiliated on screen? "These reactions are triggered by empathy: feeling the same thing we believe someone else is feeling," Gjersoe says. "Empathy allows us to put ourselves in someone else's shoes."

"Brain imaging studies have shown that there is a great deal of crossover in brain networks when we experience pain ourselves and when we observe others in pain. For example, people shown videos of patients being injected in the mouth showed activation in many of the same parts of the brain as if they themselves were being injected in the mouth."

So when we turn on footage of people cycling down incredibly steep precipices or dangling from precarious overhangs, part of our physical nervousness on their behalf is because we are imagining ourselves in their situation and how scared we would be.

Another contributing factor might be the fact that the sympathetic nervous system, which coordinates our fight or flight response, may not differentiate that much between real and not real.

"Visual information that conveys a threat might be translated directly into feelings of anxiety or urgency, which in turn trigger responses such as muscle contractions or increased heart rate," Gjersoe explains.

Tamar Gendler, a Yale University psychologist, has proposed that we have two cognitive states for reacting to events in the world.

The first is our beliefs – those things that we believe to be true. We can say with considerable confidence that the protagonist of the movie will be okay in the end and that zombies will not subsequently break into our home and eat us.

The second cognitive state, Gendler suggests, is our 'aliefs.' These states are triggered by associations, instead of consideration, and can be either conscious or unconscious. We then feel uneasy even though there is no direct threat to us.