However, people who rely solely on walking or other aerobic type activities for improved physical function and enhanced personal appearance are likely to be disappointed. As good as walking is for the cardiovascular system, it offers little in the way of muscular conditioning. Walking does not replace the muscle tissue we lose at the rate of ½ to 1 pound per year during our midlife years, nor does it prepare us for more strength dependent activities such as spading, hoeing, raking, hedge-trimming, sawing, and working around the yard and garden.

To increase muscle size and strength, it is necessary to do some form of resistance exercise. Resistance exercise can be performed at home with elastic bands, dumbbells and barbells, or at a fitness facility using specifically designed weightstack machines.

Unlike endurance exercise that is characterized by low-intensity activity and long duration, resistance training involves high-intensity activity for a short duration. That is, the resistance should be heavy enough to fatigue the muscles within 8 to 12 controlled repetitions of the exercise. This requires just 50 to 70 seconds of muscle effort, and each resistance exercise is performed only once. To condition all of the major muscle groups you should do 8 to 15 resistance exercises, which requires about 15 to 30 minutes per training session.

If the primary purpose of your exercise program is to lose weight, you should also include resistance exercise. While it is true that resistance training is the best means for building muscle and bone, it is also the best exercise for reducing body fat. Compare the number of calories used on a weekly basis from three 30-minute walks and three 30-minute resistance training sessions.

Walking For 30 Minutes/Day, 3 Days/Week

Resistance Training For 30 Minutes/Day, 3 Days/Week

As you can see, resistance training burns about the same number of calories as walking over a 30-minute exercise session. However, due to the anaerobic nature of resistance training, it generates greater calorie utilization during the recovery period following the exercise session. The biggest benefit of resistance training, however, is the addition of new muscle that requires more energy all day long. A pound of new muscle uses 30 to 50 calories a day for tissue maintenance, and that really adds up over a week's time.

Our research studies show that adults and seniors add about one pound of muscle every four weeks during the first few months of resistance training. This additional muscle tissue increases resting metabolism by about 100 calories per day or over 700 calories per week after three months of regular strength exercise. This metabolic increase is undoubtedly a major factor in the fat loss experienced by the research program participants.

So, resistance exercise is actually more effective than aerobic activity for reducing fat and improving body composition. Nonetheless, I strongly advise a combination of regular resistance exercise (two or three days per week) and aerobic activity such as walking, cycling or swimming (four to six days per week). In fact, this is essentially the physical conditioning program performed by our research class members.

If you would like more information on resistance training or our research programs please plan to attend my spring fitness slide presentation on Monday, March 30th, 6:00 p.m. at the South Shore YMCA. There is no charge for the presentation, but please call Susan Ramsden at (617) 479-8500, x132 to help us make seating arrangements.

Wayne L. Westcott, Ph.D., is fitness research director at the South Shore YMCA in Quincy, MA. He is editorial advisor for many publications, including Shape Magazine, Prevention Magazine, Club Industry Magazine, and Men's Health Magazine, and author of several fitness books including the new releases, Building Strength and Stamina and Strength Training Past 50.