Did you know there are over 600 muscles in the human body? And of those 600 muscles, which are located anywhere from your eyes to your toes, only about ten are used during any given workout. Of course we aren’t going to exercise our foreheads or tongue, but what about the other major muscles that get neglected in our weekly workout routine?

Many of us play favorites when picking which muscles to engage, focusing primarily on exposed areas like the legs and arms. The side effect of selective exercising is imbalances, injuries and underworked muscles that are valuable in your everyday activities.

These are the top muscles you probably have never exercised, but should:

Rotator Cuff

This area consists of four muscles that merge above the humerus (arm bone). Just as its name suggests, the rotator cuff is responsible for arm rotation at the shoulder joint. If you’ve ever injured this area of your body, you know just how valuable it is when it’s healthy.

• Hold a free weight in your right hand and lie down on your left side. Prop your head up on your left hand and stack the legs and feet. Use a light weight for this movement and do not push your shoulder past the point of comfort. The goal is to achieve maximum shoulder rotation, not strain your muscles by pushing too heavy of a load.
• Bend the right elbow at a 90 degree angle, rest it at your side and drape your forearm over your abdomen.
• Keep your elbow snug against your body as you slowly lift your right forearm up toward the ceiling. Continue to rotate at the shoulder until your forearm is perpendicular with the floor. Repeat 10-12 times then switch sides.

Gluteus Medius

The glutes are some of the most important muscles in your body. Not only do they amplify your appearance in your favorite pair of jeans, strong glutes are necessary for athletic performance and knee and hip health, as well.

Most of our workouts target the biggest muscle in your tush - the gluteus maximus. Its neglected neighbor, the gluteus medius, needs equal strength-training attention to protect and enhance hip rotation and leg stability when walking or running.

• Drop the weight but remain in the same side lying, leg stacked position as the previous exercise.
• For this movement, think of a clam shell opening and closing. Just like the clam, you will pull the right knee up and away from the left knee without separating at the feet. Your hip joint and feet will serve as your hinge as the leg moves back and forth for 25 repetitions. Once complete, repeat on the opposite leg.

Trapezius

Not to be confused with a circus act, the trapezius runs along the back and neck, and when conditioned properly helps with neck extension, shoulder stabilization and movement. If you are hunched over a desk all day or lug around an oversized book bag, you’ve most likely experienced the knots associated with strained or underworked trapezius muscles.

For this exercise you can simply use your body weight or increase the challenge by incorporating a light weight in the form of dumbbells or a resistance band.

• Stand tall with your shoulders back, chest up, core tight and chin tucked. Extend your arms out in front of the body at shoulder height.
• Gently pull your arms away from your body until you feel a stretch in the chest and tightness between the shoulder blades. Hold this position for five counts, squeezing your shoulder blades as if you are trying to hold a ping pong ball between them.
• Release your arms by bringing them back to the starting stance. Repeat this exercise 10-12 times.

Don’t let missed muscles throw your body off balance.

This article was originally featured on Philly.com