Q. My husband and I have been having an argument. He wants us to join a gym — at 70. I don’t see any purpose at all to paying money to go somewhere to exercise when we can do just as well walking around the block or pulling weeds in the garden. Now the kids have joined in (on his side) and given us a three-month trial membership to this local fitness club. I’m expecting you to talk some sense into this ridiculous family dispute.

A. Sorry, I’m pretty much on their side. You are right, of course, you can develop your own exercise program at home. But walking isn’t enough, nor is weeding the garden. I read recently about a couple in their late 80s who have been going to a gym for two hours a day since the day the husband retired.

Here is the advantage to the gym. You need an exercise program that combines three elements in balance: cardiovascular to strengthen your heart (the walking is good for that); stretching and flexibility to keep your muscular range of motion from stiffening up; and strength training to keep the natural aging process from weakening your muscles. At the gym, a trainer can help you design a regime that addresses all three areas.

Here’s another benefit. It’s fun to do the exercises with other people. You’ll make a few new friends at the gym and broaden your social horizons as well as your physical ones. There’s also something to be said motivationally for “having paid for it.” Investing a little money will help urge you on.

The American Academy of Orthopedic Surgeons gives these guidelines on exercising:

• Balance. Your workouts should be balanced between cardiovascular exercise, strength training and flexibility exercises.
• Variety. Embrace cross training. You should participate in a variety of activities each week. Concentrating on one activity of sport can lead to activity-related repetitive injuries.
• Form. Always use proper form. Slow, controlled movements are often best. If you’re unsure about the proper form, consult a trainer.
• Stretching. Many people underrate the importance of warming up and stretching. Before your workout, spend some time jogging in place or doing jumping jacks to warm up your muscles so that you can stretch them easily. Never bounce while stretching and never try to stretch without warming your muscles up.
• Equipment. Buy and use the proper safety equipment for your activity (a helmet for biking, for example). Make sure everything fits comfortably and properly. Your shoes should match your activity and should be worn only for that activity.
• The 10 percent rule. When increasing your activity, do not add more than 10 percent per week. For example, if you usually run five miles a day but want to run 10, build up to that by increasing your mileage by 10 percent a week. The 10 percent rule also works for increasing the amount of weight you lift in your strength-training workouts.
• Fuel. Proper diet and fluid intake is crucial. Don’t work out on an empty stomach. Try to eat a small meal before. Make sure you drink plenty of water before, during and after activity, especially in hot weather.
• Rest. Allow time for your body to recover and adapt to activity, especially if trying something new. “Relative rest,” like walking or swimming one day if you usually run, will help you avoid overtraining.
• Listen to your body. It usually gives you clues when things are not right. You may have a previous injury or a new ailment that needs special consideration. Seek the advice of a sports-medicine specialist if you have any pre-existing conditions that may make exercise difficult for you. A specialist can develop a custom program to meet your specific needs.

So begin some kind of exercise program with your husband. By the way, if you two have led sedentary lives for a few years, check with your doctor before making a change.