Taking an outdoor fitness class lets you get fit in the fresh air, much like going on a hike or picking really heavy berries. Embrace nature with this Groupon.

Choose Between Two Options

• $45 for one month of outdoor boot camp classes ($99 value)
• $79 for two months of outdoor boot camp classes ($198 value)

Kettlebells: Holistic Heaving

Although the upswing in kettlebell workouts may seem recent, they’ve been around for ages. Find out where they come from and what they do with Groupon’s look.

Philosophers could spend an age arguing whether the kettlebell has remained a fitness staple because of its simple design (it’s nothing more than a spherical cast-iron weight with a handle) or in spite of it. Either way, its longevity speaks to its efficacy. Unlike traditional weights, kettlebells often demand a buildup of momentum to perform dynamic actions such as the kettlebell swing, a maneuver that requires participants to bring the weight in a fast arc from behind the inner thighs to arm's length in front of the chest. These types of movements work multiple muscles at once, forcing them to combat the centrifugal forces generated by the kettlebell's path and achieve stabilization. Because the center of gravity resides outside the hand, they also allow for more fluid mobility than dumbbells or barbells. The result is an intense workout with a full-body focus.

Russian strongmen began hefting kettlebells in the 18th century before the Soviet military incorporated them into their training drills. Since then, kettlebells have made their way into the civilian realm, remaining an active force in fitness regimens around the world—they even helped actor Gerard Butler tone up for his starring role in the film 300. A 2010 study conducted by the American Council on Exercise found that a 20-minute kettlebell workout might burn the same number of calories, on average, as 20 minutes of running at a six-minute-mile pace or rapidly cross-country skiing uphill.