GRAND BAHAMA ISLAND -- Last fall, four young people dipped the back tires of their bikes in the Alaskan waters of Prudhoe Bay and started to pedal south.

They pedaled 308 days and 14 hours through 16 countries (including Nicaragua and El Salvador) and, finally, last week, dipped their front tires in the even colder waters of Ushuaia, Argentina.

Their journey, 16,000 miles, appears to be the longest continuous bike trip in the world.

To make sure, I added a mile to the trip by inviting the four of them to spend some time here on Grand Bahama. They arrived by boat at the Underwater Explorer Society's docks, and I pedaled with them that short distance to my house, always making sure to stay in the lead.

I have filed away that short jaunt in my memory as "the time I beat the world-record bikers," and plan to drop the comment many times in future years. Half truths can sound so nice.

As you would expect, the bikers are brimming with stories.

Medical students Martin Engel, 28, and Anne Knabe, 25, the only woman on the journey, probably had the closest mortality calls. While biking through a remote area in Mexico, the group was ambushed by bandits with machetes. Two bandits aimed their machetes and threw them at Martin and Anne. They hit with full force, butt-first rather than blade-first.

Business major Bret Anderson, 25, had a close call of a different sort. On a rock-strewn, cliff-like pass in Columbia, Bret lost control of his bike and slid from the pass, coming to a stop just in time to see a 1,000-foot drop under his front tire. He did not move. And then he backed up carefully (I would imagine with the tenderness of one walking on nitroglycerine) and started down the pass again very slowly. At which time an avalanche struck and nearly pushed him over the edge again.

Dan Buettner, 27, my writer friend who conceived and orchestrated the trip, rode approximately 15,999 miles without "wiping out." But as he rounded the final ice-covered hill (it's winter in Argentina now), with the end in easy sight, his bicycle gears and brakes froze.

The bike flipped and Buettner traveled the last 100 feet of his trek on his derrier. He still has to gently ease himself into a chair.

The most serious injury happened to Engel. A dog ripped a 17-stitch bite in his leg -- as Martin hung up his clothes to dry on the roof of a hotel at the end of the trip.

All of the bikers agree that the first and last day of the entire journey were the hardest. The first day biking in Alaska was hard because their legs had become weak from riding in a van for five days (what does that say about how easily our bodies get out of shape?). The last day was tough because of the wind and exceptional cold. The temperature didn't rise above 10 degrees and the wind blew with a fury that constantly pushed their bikes backwards.

And after all this -- the fear and the heat and the cold and, I am sure, the pain and at times the misery -- do you know what these bikers did the day after completing their fantastic journey? For fun, in the 10-degree cold, they rode their bikes around a dirt track in downtown Ushuaia, Argentina. They circled the track for about an hour, biking slower than usual, side-by-side, talking about the events of the last 308 days.

For that last ride, the bikes were outfitted just as they had been during the entire trip, and as they are in the accompanying photo. If you are a pack rat as I am, I hope you will notice how few things are needed for a journey halfway around the world.

Each bike carried a 10-month supply of summer, winter, and rain outfits in four "panniers" (like saddle bags); a front pack usually held camera, film, tool kit, and food. During the last six weeks and 2,500 miles, the pack held mostly bread and cheese, canned fish, and dried fruit. Three water bottles were fastened to the bike frame, and the sleeping bag and tent were strapped over the rear wheel.

The front packs on each bike were topped with a clear plastic, waterproof pocket. Dan Buettner's contained a completely worn-out map of South America, obviously folded hundreds of times, now folded to show Ushuaia circled in red ink. Bret's pocket usually contained vocabulary cards. Martin and Anne studied medical definitions.

During the entire trip, the bikers' muscles (including their hearts) responded to the tasks required of them. Their leg muscles, for instance, bulked up during the stretchs of really mountainous biking, when the demands on them were increasingly severe. But during the long stretches of relatively flat and easy biking, they decreased somewhat in size.

Not surprisingly, other muscles became weaker, too. Because the bikers virtually never walked or ran, a one-block walk at the end of the trip fatigued them. Even now they complain of weakness when they try to run.

"And none of us has done any upper body work at all," Bret said as the three men bikers sat around my porch. Dan Buettner had spent years lifting weights, and during many of those years had intimidated me with his strength. Bret and Martin had obviously lifted, too, but not for a while.

"Well, you know, I could take you all to the gym for a light workout, if you want," I remarked casually, "just a warm-up, you know."

Our workout started with a decline press -- body in a declining position, weight bar lowered to your chest. Decline presses look impressive to the uninitiated but they're hard to do without practice. It just happens to be my strongest exercise. I neglected to tell my friends these things and looked on innocently as they strained to match my effort.

During the next two exercises -- behind-the-neck pull-downs and lat pulls -- the bikers matched my weight and repetitions again, but their eyes glazed a bit and sweat began to pop from their young brows.

And then I demonstrated my chest routine using 35-pound dumbbells on an incline bench. The motion is somewhat akin to hugging a very large oak tree while lying at an angle on your back.

After I had finished, Dan Buettner picked up my dumbbells, judged the weight, and without saying a word exchanged them for a lighter set. The grunts nevertheless became quite audible.

And then I handed each of the bikers a pair of 10-pound dumbells. People in my gym refer to these pretty things as "la femme spa" weights. For certain exercises, however -- like the killer shoulder routine one of my doctors had taught me -- they seem very, very heavy.

Not one of my young friends made it through a set of 10 repetitions. I performed effortlessly. And I have never enjoyed a workout more.

The moral here, of course, is that practice really does make things better. You notice that I did not try to compete with the bikers on leg exercises. And within weeks, I would not have been able to compete with them on upper-body exercises, either.

Our bodies respond quickly. If you, for instance, haven't been biking for years, I would like for you to remember the exhilaration and freedom biking first brought you as a child. That same feeling can happen now, and can make you a healthier person, too -- sooner than you think.

I myself am adjusting the seat of the 18-speed touring bike with 16,000 miles on it that Martin Engel gave me. I plan to ride it with pride and a proper sense of respect. I may have beat these guys with a trick or two in the gym, but I can't touch what these four young people have accomplished in their world's record bike trek across the Americas.