Boxing Class: 287 calories per half hour
Don't worry, you won't actually have to hit someone if you take a boxing class. Instead, you'll hit punching bags and shadow box (throw punches that don't make contact with anything), which is more challenging than it sounds. Your boxing instructor will likely lead you through some traditional calisthenics (be sure to skip the jumping jacks and burpees, which are high-impact) as well as squats, wall sits and sit-ups. If you explain your needs or limitations ahead of time, a good instructor will offer you alternate moves for jumping exercises. Note that some boxing classes also involve various kicking drills. Keeping one foot on the ground at all times will keep your joints a little safer, so skip any jumping or hinge kicks.
Rowing Machine: 281 calories per half hour
Few cardio workouts work your body from head to toe—without impact—the way rowing does. If you use proper form, a rowing machine will target all your major muscle groups, as well as provide a serious cardiovascular challenge for any fitness level. You can control the intensity of the workout by increasing or decreasing the resistance of the machine and/or your own speed. To increase the calorie burn, try doing intervals of one minute of all-out effort, followed by a minute or two of lower intensity to catch your breath. Repeat the intervals 10 times to start. You can experiment with adjusting the length of time you spend at max effort versus recovery, as well as the number of intervals you complete per session.
Circuit Training: 264 calories per half hour
Circuit training adds an aerobic challenge to resistance training by alternating between different muscle-strengthening exercises with little to no rest between exercises. This elevates the heart rate and makes for a super-efficient workout. Many bootcamp-style fitness classes use circuits to burn calories and build muscles at the same time. You can design your own circuit workouts using simple equipment like dumbbells, medicine balls and even your own body weight.
Spinning: 238 calories per half hour
Although Spinning (indoor cycling) happens in a class environment, it's a very personal workout: You control everything from your speed to your resistance level, and no one but you knows just how hard you're working (or if you're taking it easy). Spinning is perfect for people who can't follow the choreography of a typical aerobics class since all you have to do is pedal a stationary bike. But if you push yourself, you certainly feel a burn in your lungs and your legs that means you're building strength and endurance. If it's your first class, make sure your instructor helps you set up your bike properly; this will help keep your joints at the proper angle and alignment so that they don't become irritated or painful as you ride. At first, your "seat" will likely be sore after class but that should diminish over time. You can also wear padded bike shorts to ease the discomfort.