Flexibility exercises use gentle, stretching movements to increase the length of your muscles and the effective range of motion in your joints. They may consist of a series of specific stretching exercises, or be part of a larger exercise program such as yoga, pilates or dance classes. Because one of the main goals of stretching is to lengthen the connective tissue surrounding your muscle fibers, flexibility exercises should be done after you've already warmed up your muscles with a few minutes of aerobic activity. A typical session involves a minute or two on each stretching exercise.

Although flexibility exercise don't offer the dramatic overall benefits of aerobic or resistance exercise, regular stretching (several times a week) can be an important way to maintain your body's mobility and freedom of movement, particularly as you get older. Stretching exercises can also improve your posture and are an essential part of effective long-term treatment for strained or chronically sore backs (one of the most common complaints among American adults).

Flexibility exercises can be an important part of an injury prevention or rehabilitation program if chronically tight muscle groups contribute to the problem. You may also find that a few minutes a day of gentle stretching can be very relaxing, physically and mentally.

Only light stretches for limbering up should be done before beginning an exercise session - any flexibility gains from stretching when your muscles aren't fully warmed up are strictly temporary.

All stretching move-ments should be done slowly, to the point where you feel a gentle pleasant tension in the muscle being stretched.

For an effective stretch, you need to hold this position for 15 to 30 seconds.

Never bounce as you hold a stretch, be-cause this will acti-vate your stretch reflex (an automatic, protective contrac-tion).

As you relax and hold the stretch, breathe easily through your nostrils and concentrate on maintaining a feeling of pleasant tension in your muscles. If you feel any pain, stop immediately.

If you regularly stretch your muscles after they're fully warmed up - at the end of an aerobic workout, for example - you can gradually increase their resting length by lengthening the connective tissue that surrounds your muscle fibers. Improving flexibility in this way will make movement easier and more fluid and can also help prevent back pain, sciatica and other repetitive-motion injuries caused by tight muscles.

The more often you stretch, the more you'll lengthen your muscles. For maximum benefits, do your stretching routine several times each week.

Calf Stretch
Stand comfortably with your hands on your hips, or place both hands on a wall (shoulder's width apart), and step forward with your right foot (about a half-shoulder's width). Bend both knees, keeping your feet flat on the floor, and shift your weight to your forward foot. Slowly lower your hips, until you feel a gentle stretching sensation in the calf muscle and Achilles tendon of your left (rear) leg. Hold for 15 to 30 seconds, then switch legs and repeat.

Hip Flexor Stretch
Step forward with your left leg (about a shoulder's width), and - keeping your left foot flat on the ground - lower your right knee so that your knee and toe rest on the ground. Your left (forward) knee should be directly above your left ankle. Gently lower your right (rear) hip, until you feel a gentle stretching sensation in the front of the hip. Hold for 15 to 30 seconds, then switch legs and repeat.

Hamstring Stretch
Sit comfortably on the floor with your right leg straight and your left leg bent, so that the sole of your left foot rests flat against the inside of your right leg. Slowly curl your upper body down toward your right knee until you feel a gentle stretching sensation in your right hamstring. Hold for 15 to 30 seconds, then switch legs and repeat.

Shoulder Stretch
Standing comfortably, lace your fingers behind your back so that your palms are facing in toward your spine, thumbs pointing down at the ground. Slowly raise your linked hands up toward the ceiling, keeping your neck and back relaxed, until you feel a gentle stretching sensation in the front of your chest. Hold for 15 to 30 seconds.

Triceps Stretch
Bend your right arm behind your neck, so that your right elbow points to the ceiling. Grasp your right elbow with your left hand and pull it gently to the left, until you feel a stretching sensation at the back of your upper right arm. Hold for 15 to 30 seconds, then switch arms and repeat.

Lower Back Stretch
Lie on your back with both legs extended straight out. Bend your right knee and clasp it with both hands, then slowly pull the knee toward your chest as far is it will comfortably go. Breathe in deeply then exhale, relaxing and pulling the knee closer as you breathe out. Repeat this breathing action several times as you hold the stretch for 15 to 30 seconds. Then switch legs and repeat.

Mad Cat Stretch
Position yourself comfortably on your hands and knees, with your back horizontal and your eyes looking forward. Exhale slowly and contract your stomach muscles while allowing your head to hang down, so that your back curves upward like a dome. Hold for several seconds, then return to starting position, inhaling as you do. Repeat five to 10 times.

Back Extension Exercise
Lie on your stomach and stretch your head upward with your arms extended in front of you, forearms flat against the floor (your elbows should be directly under your shoulders). Leaning comfortably on your forearms, hold this stretch for two to five minutes. (Concentrate on relaxing and breathing deeply.)