Even if you go on a cruise ship, you don’t have to leave your running shoes back home.That’s what I found out during a recent four-day cruise to Cozumel, Mexico with my girlfriend Laura. The amenities aboard the 1,112-foot Royal Caribbean cruise ship “Liberty of the Seas” include a mile-long running track 12 levels above the sea.Last Friday morning, on the first full day of the cruise across the Gulf of Mexico, I laced up my trusty New Balances and took the elevator to the track, a well-outlined oval on the deck lined by beach chairs.The sea rocked gently beneath me as I did a few stretches, then started my first lap. It felt mostly refreshing to get out there in the early morning, before the sun began to increase in intensity. Outside of my lone treadmill run, this was the first time I have run over a moving surface and certainly the first time I’ve run over the ocean.You could consider the ocean the ultimate treadmill, one that not only pulls you forward and back, but also rises and falls to its own rhythm. On this morning run, at least, that rhythm was gentle ? practically imperceptible. Ironically, while the seas were calm, the winds offered resistance periodically.It helped to have some company. Quite a few fellow passengers shared the track – both runners and walkers, men and women. All around us stretched the waters of the Gulf. On the side of the track were signs suggesting various stretching exercises for parts of the body, including one for the core.As I ran, I tried to pay attention to where I was landing. The night before, the ship’s spa had offered a foot-alignment session where a staff member examined the type of imprint our feet left as we walked. I left the session noting that I landed on my big toe a little too hard, which could lead to problems with my knees and lower back, and that orthotics might be a good idea. So my goal on the morning run was to land gently on the entire front part of my foot, like barefoot runners do (only with shoes).After four laps around the track, my feet, knees and back all felt fine, but my legs felt rubbery. I took a farewell lap, walking it this time, just as more runners seemed to be arriving.If you go on a cruise, running opportunities like this might not be hard to find. The Royal Caribbean website informs readers that “You’ll find running tracks on every ship in our fleet. The tracks are open to anyone, but proper shoes are recommended.” The company also offers self-guided running maps at several of its ports, such as Labadee, Haiti, which has a fitness path. There are other options for fitness on board. On the “Liberty of the Seas,” these options ranged from a basketball/volleyball court, a 9-hole miniature golf course, swimming pools, a place to practice surfing and boogie boarding, and even a rock climbing wall.What running on a cruise ship shows is that once you get your sea legs, your running legs will come back just fine.Rich Tenorio can be reached at [email protected].