Take the Weight-Training Safety Quiz

It's important to maintain your muscular strength, endurance, flexibility, and cardio-respiratory endurance to live a healthy life. As you age, you can lose up to 1 percent of your strength each year after age 25, the American College of Sports Medicine says. Aging doesn't mean that loss of strength, energy, and fitness are inevitable, however. According to the President's Council on Physical Fitness and Sports (PCPFS), much of the frailty associated with aging is actually the result of inactivity, disease, or poor nutrition. Weight training can keep you fit, as well as help prevent injury.

In fact, if you are older than 35 and have been inactive for several years, or you have one of the following conditions, you should check with your doctor before beginning any new exercise program, according to the PCPFS:

• High blood pressure
• Heart trouble
• Family history of early stroke or heart attack death
• Frequent dizzy spells
• Breathlessness after mild exertion
• Arthritis or other bone/joint problems
• Severe muscular, ligament, or tendon problems
• Obesity

Also, always use a spotter when doing bench presses and squats, and lift with a buddy, whenever possible.

Wear good athletic shoes that provide firm floor traction.

Free weights are more easily adapted to smaller and larger body types. But machines are safer than most free weights because the weight is more controlled.

Include at least one exercise for the upper back, shoulders, chest, lower back, abdominals, front of arms (biceps), back of arms (triceps), buttocks, front of thighs (quadriceps), back of thighs (hamstrings), and lower legs. Different exercises that work the same muscle groups can be done on alternate workout days, say fitness experts at Indiana University. To improve muscular strength, you should do a minimum of two sessions per week that include exercises for all major muscle groups, says the CDC. To increase muscular endurance, you should do at least three sessions per week that include exercises such as calisthenics, push-ups, sit-ups, pull-ups, and weight training for all major muscle groups.

Muscles need time to repair and rebuild after a workout—that's what makes them stronger. Doing weight training two to three times a week will allow enough time for rest, but give enough of a workout to significantly boost your strength, IU experts say.

For instance, bench presses and squats should be done before triceps push-downs and leg extensions, IU experts say.

Once you have hit your stride, 30 seconds to 2 minutes of rest should be sufficient. Beginners may need to rest a little longer.

Keep breathing. Holding your breath raises blood pressure, possibly to dangerous levels. Exhale on exertion.