1. Running
Running is one of best activities you can do. It doesn't require special equipment (except some quality shoes) and you can do it anywhere. Best of all, you burn serious calories, especially if you add hills and sprints. A 145-lb person can burn 300 (at 5.2 mph) in 30 minutes. The downside is, it takes lots of practice and you should watch your knees and ankles for any discomfort or pain.
2. Bicycling
Outdoors or indoors, cycling gives some great cardio. Using all the power in your legs, you'll increase endurance while burning lots of calories, anywhere from 250-500 in 30 minutes, depending on how fast you go and how high your resistance is.
3. Elliptical Training
The elliptical trainer is a great way to build endurance while protecting your aching joints from high impact activities. Plus, if you use one with arms, it's just like using a cross-country ski machine. The elliptical trainer is also a good choice for runners looking for a break from pounding the pavement. A 145-lb person burns about 300 calories in 30 minutes.
4. Swimming
Swimming is a full body exercise. The more body parts you involve in your workout, the more calories you'll burn. Spend 30 minutes doing the breastroke and you'll burn almost 400 calories. Best of all, your joints are fully supported so you don't have to worry about high-impact injuries. It's also great cross-training for other cardio activities.
