When the temperature drops this winter, don't let your motivation for exercise fall along with it.

Cold weather doesn't have to put a chill on your fitness routine, even if the treadmill or stair-stepper seems boring compared with jogging or riding your bike outside. It is important to ask yourself: How can I make exercise different to make it more motivating?

If you're seeking an answer, you may want to consider these five indoor fitness choices. Some build on familiar activities, but others may be new to you. Always keep some variety in your exercise routines to prevent boredom and drop out. If you haven't been exercising regularly, be sure to check with your doctor before starting a new exercise routine.

Kickboxing uses martial arts kicks and punches in an aerobic class setting. Kickboxing is a high-intensity exercise. A 135-pound person is likely to burn 350 calories to 450 calories during a 50-minute class.

Participants need to take steps to prevent injury, especially muscle strains and joint problems. If you're a beginner, start slowly and work up to more complicated moves.

A pool workout isn't limited to the endless back-and-forth of lap swimming, thanks to water aerobics and other classes that take place in pools.

Because the effects of gravity decrease in the water, a pool workout is easy on the joints. Water is also about 12 times thicker than air. That increases resistance, so moving through water also gives you cardiovascular benefits as you build strength.

The pool can provide a workout at a high intensity with almost no impact, a real plus, especially as you get older. People recovering from injuries and women after pregnancy can also gain a lot from a water workout.

You still sweat, even in the pool, so drink before you feel thirsty to remain hydrated. Also, because blood flows more easily when you're in the water, your heart rate will be lower than it would be using the same intensity on land. Pay attention to your breathing and how tired you feel so you don't overdo it.

Racquetball uses almost every muscle in your body. Your heart rate stays high even when you stop between points.

Finding a place to play should be easy. Courts are in nearly every YMCA, on many college campuses, and in many health clubs. Just be sure to protect your eyes with the correct eyewear when you play.

Being forced indoors during the winter can make you feel like climbing the walls. Look for a specially designed climbing wall at your health club or local college. Scaling a 40-foot wall using only handholds and footholds can seem scary. But even if you can't do a single chin-up, you can try a climbing wall.

Climbers always wear a safety harness. A partner on the other end of the rope is strapped in on the ground to keep any fall a short one. Climbing facilities will provide all the safety equipment and climbing shoes.

If riding the stationary bike is getting old, you might want to try indoor cycling. This is often called spinning. Indoor cycling classes are instructor-led fitness classes taught on stationary bikes accompanied by music. The instructor takes you on a virtual ride, changing the speed and resistance.

Indoor cycling tones the lower body, works your heart and lungs, and burns 350 calories to 600 calories per 45-minute class. Calories burned depend on your size and the intensity level of the class. The classes can be high intensity and are generally not for a person who is just beginning to exercise. Even so, most instructors do encourage participants to go at their own pace. This can be helpful as you get into better shape.