Q. My boyfriend says that running is the best way to lose weight and get fit. However, I don't like running and prefer to take step or Spinning classes, along with lifting weights. Is my program as effective as running is?

A. Actually, your program is more effective because you combine cardiovascular exercise with strength training, says San Diego fitness consultant Richard Cotton, M.A., a spokesman for the American Council on Exercise. Running is an excellent way to burn calories and strengthen your heart and lungs, but it won't build muscle mass or strength. Research shows that runners who don't lift weights lose muscle at the same rate as sedentary people do - about 30 percent from age 30 to 70. However, people who lift weights regularly can preserve most of their muscle mass throughout life. This means they maintain a higher metabolism and are less prone to weight gain.

You can tell your boyfriend that running places more stress on the body than step or Spinning do, increasing the risk for joint injuries. "Running beats you up more," Cotton says. Both Spinning and step are plenty effective for cardiovascular fitness and calorie burning, although with step there is a "point of diminishing returns," Cotton says. "You can always run or pedal faster, but you can't always step faster or higher." Alternating step and group cycling classes is a great idea.

The bottom line: You'll only stick with activities you enjoy. If you thrive on the energy of group exercise and are inspired by the instructor, you've made the best choice for you.