Use it or lose it! Without exercise, your body naturally will lose muscle with each passing decade.

Less muscle means a lower metabolism, which accelerates an increase in body fat. With summer and “beach bodies,” it’s time to get serious about exercising. The muscles respond positively to weight training, increasing your metabolic rate, raising HDL levels (the good cholesterol) and aiding in lowering blood pressure.

Many trainees do exercises that are easy and avoid the hard ones. Like the men who walk into the gym and head for the chest machines or the women wanting to work only their legs.

So here’s how to get your muscles working. The pectoral machine, for example, is often one of the most difficult for women. So on your next chest day, start with this exercise that works the chest muscles — the pectoralis major and the pectoralis minor and to a lesser extent the anterior deltoid.

It is important to use proper form when working the chest muscles, as they can be very brittle and tear easily. Reattachment may require surgery. Adjust the seat so that when you are seated and your elbows are resting against the pads of the machine, you are not reaching up or down. The machine arm pads should be at shoulder height.

Select 10 pounds for women and 15 pounds for men. This exercise focuses on the position of the elbow, not the hands. Sit down and place your arms against the pads. Begin the exercise by squeezing your elbows together and then slowly returning your arms back until they are even with your body. Then squeeze them together for your second repetition. Perform 15 reps.

Then get out of the machine and increase the weight five pounds for your second set of 12 repetitions. As the chest fatigues, the elbows will have a tendency to rise off the pads with the hands increasingly pressing more. Don’t allow this. To compensate, I have trainees put their arms straight out and turn their palms slightly up toward the ceiling and then in a long sweeping motion squeeze the elbows together. Again, watch for the hands to turn down and the elbows to raise up; this is your signal that it’s time to stop and psych up for your next set.

After your second set of 12 reps, increase again by five pounds and perform 10 repetitions. Your movement together is deliberate and should be completed in two seconds with the return under control and completed in four seconds. For your final set, increase the weight five pounds and perform eight repetitions.

For proper training, you need to lead your body rather than letting your body lead you.