Over the years you've perfected your gym routine. You hit your pecs, lats, bi's, and tri's on a consistent basis. But is this to your downfall?

Sure, these mirror muscles garner attention on the beach in the summer and fill out a sweater in the winter. However, you're probably neglecting some lesser-known groups that play an important role in injury prevention. We've highlighted what they are, what they do, and how to train them.

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The muscle: Brachialis

Where it is: In the upper arm, deep in your biceps.

What it does: Flexes the elbow. This is the muscle that makes your arms look bigger. When doing a biceps curl, the brachialis is the prime mover, not your biceps.

How to train it: Chinups or any variation of the standard curl.

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The muscle: Levator Scapulae

Where it is: Connects your neck and skull with your shoulder blade, on the back side.

What it does: Elevates your shoulder blades. When you shrug, it's this muscle doing majority of the work. It also helps keep your shoulder blade stable during rotations and presses.

How to train it: Shrugs or neck extensions.

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The muscle: Popliteus

Where it is: Just below your knee, on the uppermost portion of the tibia (shinbone).

What it does: Unlocks the knees when you walk or stand, encouraging blood to return to your heart. Also rotates the femur and tibia. This muscle is responsible for most knee stability, and is important to pay attention to in order to walk correctly, which helps prevent hip injuries and sciatica.

How to train it: Squats and deadlifts.

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The muscle: Piriformis

Where it is: Deep within the gluteal muscles, behind your gluteus maximus, near your hip joint.

What it does: It rotates your knee to point out. Ultimately, it's important to keep this muscle loose and strong, as it can irritate the sciatic nerve, leading to pain when walking, sitting, standing, or any variation thereof. The external rotation of the knee is important so the knees don’t buckle, which can lead to meniscus tears in the knee.

How to train it: Squats, deadlifts, kettlebell swings, or barbell hip thrusts

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The muscle: Iliopsoas Group

Where it is: On the front of your hip.

What it does: Commonly known as the hip flexor, this muscle is responsible for bringing your knee toward your chest. It's often overworked during crunches, taking the lower abs out of the movement, and super tight for most guys. Keeping this muscle loose and strong promotes proper spinal alignment and reduces hip and back pain associated with sitting at a desk all day.

How to train it: Squats, hanging leg or knee raises, and jackknife crunches

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