I decided to bicycle from Duluth to La Crosse, Wis., during the hottest stretch of days in one of the hottest summers on record in the late 1970s. I had never done long-distance bicycling, and it hadn’t occurred to me that I needed to prepare. I was 20 years old. I was young and strong, I loved to ride my bike, and I figured that biking to the Wisconsin river city wouldn’t be that different from biking around Duluth and up the North Shore; it would just take longer.

I did not train. I did not do any research. I did not pack supplements or vitamins. I just stuffed my red pannier bags with a couple of changes of clothes, a tent and a sleeping bag, and pedaled off.

It’s about 250 miles from Duluth to La Crosse, down two-lane highways that eventually crisscross the Mississippi River and hug the banks on either side. The river bluffs get hilly and steep, but the views are beautiful, and I figured the views would be worth the pain. The trip, I reckoned, would take about five days.

I had a map. It wasn’t a very good map. I wasted most of one afternoon going the wrong direction on a gravel road and ending up back where I’d started. Fortunately, it was near a little country bar, so I had a cheeseburger and a malt, and then pedaled on into the hot and fading sun.

By the third day the backs of my hands had become terribly burned; it had not occurred to me that grasping bicycle handles for hours on end and exposing my hands to the sun, like an offering, might be a problem. When I awoke that third morning, they were a deep, hot red, excruciating to touch. I could barely move my fingers.

I gave it a little thought, and then I bicycled to a drugstore and bought a roll of medical gauze, which I wrapped mummy-like around my hands. It didn’t help the pain, but it helped protect them from further burning.

One afternoon a tremendous rainstorm blew in. The rain came down in torrents, and I hid, bicycle and all, inside a stuffy and spidery outhouse until the weather passed. Then I climbed back onto my orange Schwinn 10-speed and bicycled on.

I was sweating all the time. Out on the highway, on the blacktop, the heat shimmered up from the road and beat down from the sun, and I was caught between, a small, sweating, frizzy, sunburned fool in a cotton T-shirt and increasingly grubby shorts. There was no possibility of shade. Hour after hour, my gauze fluttering in the breeze, I pedaled, my wet shirt stuck to my back, my face red, my legs aching. It was unbelievably, unrelentingly hot.

That fourth afternoon I arrived at Winona, Minn. I was so tired, so hot, so exhausted that I cycled into the town park, got off my bike, and fell asleep in the grass.

I woke up dizzy, disoriented, my head swimming. I figured I had had too much sun and I just needed to cool off, but I was too tired to move. I threw up, and then I lay down again and fell back asleep. I awoke again and tried to get to the drinking fountain, but I couldn’t walk. The ground felt like it was rising and heaving, and I couldn’t keep my balance. I crawled. At the fountain, I hauled myself up and drank some water and tried to stick my head under the faucet. I threw up again.

I lay back down in the grass.

And then I heard a voice. “Hi, there! Do you need some potassium?” I opened one eye and saw a friendly-looking man bounding down the stairs of a nearby house and jogging toward me. He was wearing a YMCA T-shirt. He had something in his closed hand.

I moaned him away. “I don’t want anything,” I said.

“I brought you some potassium pills,” he said. “And some magnesium. And a vitamin C pill. And some orange juice.”

“I can’t keep anything down,” I said. I shut my eyes again. The world was spinning, and all I wanted was to sleep. It had been hours since I first lay down in the park, and if I had been thinking clearly I would have realized that my problem wasn’t that I was overheated — I wasn’t hot any longer, I was shivering — but I wasn’t thinking clearly.

“Just give it a try,” he said. He opened his hand and showed me three pills. Now, you may think it reckless to take strange pills in an unfamiliar park handed to you by a man you’ve never seen before, but I took them. I drank the orange juice. And a remarkable thing happened. Within a few minutes, I was able to sit up. I could look at him. I didn’t fall over. I didn’t throw up. I started to feel a little better. I sat still and rested, and the ground slowly quit its heaving and buckling.

The man told me that a few weeks before a young woman had died after jogging in that very park. Your body loses potassium through perspiration, he said, and if you don’t replenish it you can get depleted pretty quickly in this kind of heat. Nobody had known what was wrong with the young woman — she had been running, and then she suddenly collapsed and vomited, and by the time she was at the hospital she was in a coma.

Hospital! It had never occurred to me that I needed a hospital. It hadn’t occurred to me that I was sick. I just thought I was hot and tired. And potassium! I didn’t even know what potassium was. I had no idea that bicycling out on the blacktop for 10 hours a day in 90-degree heat and eating nothing but burgers and chocolate malts was somehow a stupid thing to do. I thought I was just going for a bike ride.

“You might want to go to the grocery store and get some bananas,” the man told me gently. “They’re loaded with potassium. If you’re sweating every day, you’re losing potassium fast.”

I was feeling well enough now that I knew I could make it to the store. I was shaky, but I was no longer dizzy. “Will you do something for me?” the man asked. He held out a postcard, addressed and stamped. “Will you mail this to me when you get wherever you’re going? So I know you got there OK?”

I packed the postcard in my pannier bag. I thanked the man and handed him back his orange juice glass. I biked to the grocery store and bought four bananas. And then I found a quiet spot, pitched my tent, and slept hard all night.

The next day I ate a banana for breakfast and made it to La Crosse. No problem. 

Laurie Hertzel is the books editor at the Star Tribune.