With the weather getting warmer, it's nearly time to trade the sweatshirts for sleeveless tops and for your shoulders to once again be showcased to the world. If you're interested in building shapely and defined shoulders, your best bet is to fit in a high-volume weight-training shoulder workout two days a week.

The major muscle at your shoulders is the deltoid. The deltoid features three separate heads, including the anterior head at the front of your shoulder, the medial head at the center of your shoulder and the posterior head at the back of your shoulder. The deltoid is responsible for lifting your arm upward, out to your side and back behind you. The rotator cuff, which is a collection of four muscles surrounding your shoulder capsule, is responsible for maintaining shoulder stability.

Shoulder Workout Structure: Warm-Up, Training Session and Cool Down

Warm-up

Properly warming up the muscles, tendons and ligaments within your shoulders prior to your training session is essential for reducing your risk of injury. The shoulder joint is relatively vulnerable and injuries can arise if you push it too hard without first preparing the shoulder capsule for the extra load. A warm-up will also improve your overall workout performance.

Begin with a 3 to 5 minute walk, jog or cycle on a stationary bike to increase your overall body temperature.

Follow that general warm-up with the following shoulder-specific exercises, using no weight:

Shoulder Circles - 20 reps each direction

Lift your arms up and out to your sides so that they're parallel to the floor and then rotate them in a variety of small and large circles, first in the forward direction, then backward.

Front Raise - 20 reps

Begin with your arms down by your sides and then lift them forward and upward until your upper arms are parallel to the floor. Lower the arms and repeat.

Lateral Raise - 20 reps

Begin with your arms down by your sides and them lift them up and out to your sides until the upper arms are horizontal. Lower the arms and repeat.

Training Session

Once you've finished your warm-up, move directly onto your shoulder training session, which is provided below. The workout should take you about 30 minutes.

Cool Down

Immediately following your shoulder workout, complete a battery of shoulder stretches to help reduce tightness and encourage blood flow to the overloaded muscles and connective tissue.

Complete each of the following stretches for 30 seconds each:

Chest Stretch

Stand in a doorway and lift your arm up and out to your side so that its parallel to the floor. Use that hand to grab the inside frame of the door and then gently lean forward until you feel a slight stretch at the inside of your shoulder capsule. Switch arms.

Levator Scapula Stretch

Stand tall and reach your left hand up over your shoulder toward the space between your scapulas. Place your right hand atop your left elbow and gently press your elbow downward. Switch arms.

Cross Arm Stretch

Raise your left arm and position it across the chest. Place your right hand onto your left elbow to gently press the arm further into the chest. Switch arms.

Building Shoulder Definition: Sets, Reps and Weight

The goal of any muscle-building weight-training workout is to overload muscle fibers because the damage to the fibers is what stimulates the muscle-building process. During your days off between workouts, your body is working to heal your muscles while making them bigger so that they're better able to handle the stress of a workout.

To encourage muscle breakdown and fatigue, higher set and repetitions are ideal. Perform 3 to 4 sets of each exercise and stay in the 8 to 12 repetition range. To further encourage fatigue, give your muscles just 30 to 90 seconds of rest in between sets.

The appropriate weight to use will vary depending on the exercise. For each exercise, select a weight that allows you to do at least 8 reps, but no more than 12. The last two reps of every set should be difficult. You should feel like you're challenging yourself and yet not having to sacrifice form to finish the set.

Shoulder Exercises: Hitting the Front, Middle and Rear Deltoids

The battery of shoulder exercises below targets the front, middle and rear deltoids to give you a comprehensive shoulder-building session. Complete them in order.

Dumbbell Standing Overhead Press

With a dumbbell in each hand, hold the weights just outside your shoulders with your wrists rotated so that your palms face forward and your elbows are positioned directly below your hands. Press the dumbbells upward until your arms are fully extended. The weights should touch at the top. Slowly lower the weights back to starting position to complete the rep and then repeat.

Dumbbell Lateral Raise

With a dumbbell in each hand, stand tall with your arms down by your sides and your wrists rotated so that your palms face the outside of your thighs. Allowing just a slight bend in the elbows, raise your arms up and out to your sides until they reach shoulder height. Lower the weights to complete the rep and then repeat.

Front Plate Raise

Stand and hold a single weighted plate with both hands. Hold the weight down at the front of your upper thighs. Keeping your arms straight, lift the plate upward and forward until it becomes level with your shoulders. Slowly lower the plate back to your thighs to complete the rep and then repeat.

Dumbbell Flat Bench Rear-Delt Raise

Set an adjustable bench to a 45-degree incline. With a dumbbell in each hand, lay face forward on the bench with your feet firmly on the floor. Allow your arms to hang down toward the floor and rotate your wrists so that your palms face each other. Keeping your arms primarily straight, lift the weights up and outward until your arms are parallel to the floor. Slowly lower the weights back to starting position and then repeat.

Top Your Workout Off with a "Finisher": Ensure Deltoid Fatigue

Add a "finisher" to your workout to add volume to your session and further encourage muscle building. Select a relatively light pair of dumbbells - think 5 pounds. Complete 15 reps each of lateral raise, front raise and shoulder press, moving from one to the next without any rest.