By almost any measure, ziplining down a mountain looks like a perfectly safe activity. You’re strapped by two harnesses, one for the legs and another for the shoulders, all held together by a beefy carabiner. You wear a hardhat and two thick canvas gloves, one of which has a hard pad for braking: as you approach the end of the line, you press the glove down on the cable, slowing the descent.

There are eight ziplining cables in the Reserva Natural de Atitlán, just outside Panajachel. You hike up with two guides. One goes first to make sure you land safely on the other side. Large signs clearly proclaim: “These cables and carabiners can support 12,000 lbs.! US and EU certified!” All very reassuring.

All equipped and ready to zip.

Yet, they still make you sign a document saying you understand that ziplining carries certain risks. Ah, the timeless art of covering your ass.

It’s an incredible feeling, soaring between mountain peaks, the lush canopy rushing beneath you with the breathtaking Lake Atitlán as a background.

This is how you arrive if things go as planned.

But it’s the low tourist season. Which probably means they slack a bit on the maintenance. Which means some of the trees in the line’s path aren’t fully trimmed.

Going down the fifth cable, my right foot caught a large branch, which caused my body to pivot violently to the right. My hands were obediently resting on the pulley mechanism from which I was hanging, and so my forearm jammed into the steel rope zipping by at a high speed.

I felt an intense burn, which you’d expect from such a contact. I thought for sure the cable skinned a strip off my arm, which would leave a red and white mark. When I got unhooked from the cable, I saw that it had carved a hole into my forearm, about the size and shape of an eye. It was deep enough that if you stuck a finger inside it, it would conceal most of your fingernail. It looked like one of those little scoops for making melon balls had done its thing.

This is how you arrive if things don’t go as planned.

It didn’t bleed much. I figured the cable had pretty much burned most blood vessels shut. There was also very little pain. The nerves in that area were probably smeared along the length of the cable. I was surprised by how white it looked inside. I didn’t know raw flesh was that … pale.

What I did feel was intense dizziness. I had to do the remaining three cables strapped to one of the guides.

Raquel and Luis Roberto, a lovely couple doing the tour with me, drove me to the hospital in nearby Sololá, where they warmly and quickly took me in, starting with an X-ray to check for fractures. It was the best attention I ever received in any hospital, anywhere.

As he sewed me up, the doctor asked me where I was from. I said Brazil. With the most serious face, he started to chant my archrivals’ football cheer: Ar-gen-tina! Ar-gen-tina! In my best possible Spanish, I told him he’d better watch it, or he’d be the one needing stitches. Good times.

The stitches came off after eight days.

Friendly doctor sewed me up just right.