Susan Seubert / Norwegian Cruise Line

Cruise lines offer plenty of heart-pumping activities, including basketball beneath tropical skies on the Norwegian Epic.

By Erica Silverstein, CruiseCritic.com

If your idea of a great vacation involves daily runs in the open air, a leisurely workout in a high-tech gym or a smorgasbord of fitness classes from Pilates to Zumba, a cruise may be the perfect getaway for you.

These days, cruise ships are about more than just eating and lying in the sun, and they're attracting fitness buffs, yogis and health-conscious travelers in droves with active options both onboard and off.

Believe it or not, on a cruise you really can lose weight -- or at least break even. That's because fitness centers are growing in size to accommodate a more youthful and body-conscious passenger base and often feature state-of-the-art equipmentand180-degree sea views. Ships are breaking new ground with cutting-edge workouts like Kinesis Walls, popular TRX Suspension Training and Tour de Spin classes, plus offering trendy sessions in Pilates and tai chi.

Deck games like shuffleboard and skeet shooting have made way for onboard surfing, rock climbing, mini-golf and basketball. In port, active excursion options are plentiful. Cycling is big -- not to mention hiking, kayaking, swimming and diving. If breaking a sweat can be fun, cruise ships have found ways to offer those activities in the middle of the ocean.

Royal Caribbeanis leading the pack as the trendsetter in onboard fitness options. Its ships are the only ones afloat to offer onboard surfing, boxing and ice skating. But it's not the only line to put emphasis on fitness. Others are also expanding their gyms and their top-deck fitness options. Some of the smaller lines --SeaDream,Star Clippers,Windstar,Seabourn-- focus on water sports, with onboard marinas packed with water toys that range from kayaks to water-skis.Crystaland Seabourn are two luxury lines getting creative with gentler, senior-friendly workouts like Kinesis and walking, while river lines store bikes onboard for passengers to use ashore.

Before we list our favorite lines for fitness, here are a few tips for working out onboard.

Best onboard gym

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Breaking sweat: Best cruises for fitness