There are few workouts more hardcore than rock climbing! Whether you take to the gym rock wall or head to the cliffs for some uber-awesome climbing, you're guaranteed an epic workout. It's estimated that you can burn around 650 to 1000 calories in a single hour of rock climbing. The reason you burn so many calories is that your muscles are CONSTANTLY contracted and tensed. You have to hold yourself in place by your hands and feet, and your core is engaged to keep your body close to the rock wall. It's like doing the "Farmer's Walk" for an hour! [caption id="" align="aligncenter" width="600"] Source: cygnusconcepts.com[/caption] Even rappelling is great for burning calories! It's a lot more exhausting than you'd think, and you'll burn between 450 and 750 calories per hour. Any way you cut it, rock climbing is one of the best ways to burn calories. You'll shred the muscles of your forearms, arms, shoulders, and legs, and you'll experience a thrill that can only come from tackling the challenge of a mountain cliff!