Did you know there are more than 600 muscles in the human body? Yet only a fraction are used during any given workout.

Many of us play favorites when picking which muscles to engage, focusing primarily on exposed areas such as the legs and arms. But selective exercising could lead to imbalances and injuries in muscles that are valuable to your daily activities.

Below are three areas you probably aren't exercising, but should.

Rotator cuff. This area consists of four muscles that merge above the humerus (upper arm bone). Just as its name suggests, the rotator cuff is responsible for arm rotation at the shoulder joint. Add lying external rotations to your workout to strengthen this muscle group.

  • Lie on your left side holding a free weight in your right hand. Prop your head up with your left hand, and stack your 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 your right elbow at a 90-degree angle, draping your forearm over your abdomen.
  • Keep your elbow tight 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 to 12 times, then switch sides.
Courtesy of Ashley Greenblatt

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, they are necessary for athletic performance and knee and hip health, as well.

Most workouts target the biggest muscle in your rear — the gluteus maximus. Its neglected neighbor, the gluteus medius, needs equal attention to protect and enhance hip rotation and leg stability when walking or running. Add clamshell exercises to your workout to strengthen this muscle group.

  • Remain in the same side-lying position as the previous exercise but lose the free weight.
  • For this movement, think of a clam shell opening and closing. Pull your right knee up and away from your left knee without separating at your feet. Your hip joint and feet will serve as a hinge as your leg moves back and forth for 25 repetitions. Once complete, repeat on the opposite leg.
Courtesy of Ashley Greenblatt

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, as well as 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 tightness associated with strained or underworked trapezius muscles.

For this exercise, start with just your body weight and then increase the challenge by incorporating light free weights or a resistance band.

  • Stand tall with your shoulders back, chest up and core tight. Extend your arms out in front of your body at shoulder height.
  • Gently pull your arms apart to form a T, feeling a stretch in your chest and tightness between your 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 10 to 12 times.
Courtesy of Ashley Greenblatt

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

Ashley B. Greenblatt is a certified personal trainer and wellness coach. To learn more, visit ashleyblakefitness.com.