If sagging upper arms are your trouble spots, you need to strengthen the triceps brachii, which runs along the back of your arm from shoulder to elbow.
Various exercises develop the triceps, including the supine triceps extension. The following targets the middle, or medial, head of the triceps and is a winner for your arsenal of arm-toners. To develop your arms evenly, combine a group of triceps exercises rather than relying on one or two.
Practice this exercise with light weights. Using heavy weights will decrease your range of motion and limit the involvement of the long head of the triceps. You won't be able to extend your arms fully, or you'll have to use shoulder extension to raise heavy weights above the level of your head. Either adjustment defeats the purpose of the exercise, because a limited range of motion doesn't work the full length of the triceps and decreases flexibility in the elbow joint.
Lie on your back on an exercise bench. Place your feet flat on the floor and let your head extend slightly behind the end of the bench. If you tend to arch your lower back, bend your knees and place both feet on the bench. Use a dumbbell or a narrow-grip barbell that lets you keep your hands close together, about 6 inches apart.
To get into a starting position, hold the weight above your head with an underhand grip, palms facing backward. Bend your forearms backward and lower the weight behind and close to your head. Keep your elbows pointing up, with upper arms parallel to each other. Your elbows will flex considerably, and you should feel a slight pull in the shoulder joints, which also flex.
To perform the exercise, pull the weight up and forward over your head. Use only elbow-joint extension primarily moving the forearms to lift the weight, although your shoulder joints may extend slightly. Raise the weight until your arms extend fully and your hands are directly over your head. Your arms will be at a slight angle to your torso rather than perpendicular to it. This position keeps the triceps at an angle to stretch and lengthen its fibers and to allow stronger eccentric contractions.
Breathing naturally, you'll inhale and hold your breath as you raise the weight to your sticking point (that part of the lift in which it's most difficult to keep the weight moving). Then exhale as you slowly lower the weight by flexing your elbow joints. Maintain control in returning to the starting position to avoid hitting your head with the weight bar.
To best work the middle triceps, focus on elbow-joint extension. If you start the lift with shoulder extension, other muscles come into play and you won't work the triceps through the full range of motion.
Keeping your hands closer together by using a dumbbell or narrow-grip barbell allows the triceps to do the work. With a wide grip, most of the action takes place in the shoulder joint, which strengthens the upper back muscles instead of the triceps.
Although the supine triceps extension targets the medial triceps, you'll also work the long head if you extend your forearms fully at the end of the lifting phase. In fact, the sooner you can fully extend your arms, the greater the involvement of the long head.
The triceps brachii has three parts: the lateral, medial and long heads. At the upper end, the long head attaches to the shoulder blade (scapula) just below the shoulder joint, under the armpit.
Neither the lateral nor medial head crosses the shoulder joint. The lateral head attaches to the upper half of the long bone in the upper arm (humerus) in the middle of the bone shaft. The medial head attaches to a wide area of the lower part of the humerus and extends nearly two-thirds the length of the bone. Because of its attachment, the medial triceps is strongest in executing elbow extension, especially at the beginning of the movement.
At the lower end near the elbow, all three parts join at a common tendon that inserts on the olecranon process of the large bone in your forearm (ulna).
Points to remember:
1. Use a dumbbell or narrow-grip barbell for greater range of motion.
2. Start the movement with elbow extension, holding upper arms perpendicular to floor.
3. Raise the weights until your arms are fully extended, with your hands directly over your head.
4. Use light weights.