There are over 600 muscles in the body, so it's not surprising that we tend to overlook smaller muscle groups while overtraining the more dominant and visible ones. These less visible muscles are still important, and ignoring them can hold back your progress by making you more injury prone and keeping you from looking toned and fit. Here are 4 often-neglected muscles that you should never ignore. Aim for 3 sets of 15 for each exercise.

1. Rotator cuff
What is it: It’s the group of muscles that connect the upper arm to the shoulder blade. It’s important to target and strengthen these muscles because injuring them results in limited movement.
How to work it: Lie on your side, with your elbow rested on your hip. Lift a small weight up and down with your forearm while keeping your bicep still. Use the photos below for reference.

Rotator cuff; first position

Rotator cuff; second position

2. Forearms
What is it: The muscles between your elbow and wrist--there are about 6 of them--and they help you move your wrist. If you want to lift, you need to work them to get a tighter grip.
How to work it: You can do this one sitting down. Sit with your forearms on your thigh and hold a weight with both hands, palms down. Using only your wrist, lift the weight up and down.

3. Tibialis anterior (Shins)
What is it: The front of your calves, between your knees and feet. No, it isn’t just bone! Ever experienced shin splints? They’re caused by your calf muscles being stronger than your shins.
How to work it: Walk around on your heels to help balance these two muscles out.

4. Erector spinae (Lower Back)
What is it: The small of your back - you know, where you get the most pain? Working out your back muscles is one of the best ways to prevent future muscle pain. Of course, ask your doctor first - if your back pain isn’t muscle related, you’re going to need medical help.
How to work it: Get on your knees with your arms straight. Think of your back as a table top, as flat as you can get it, with your arms, shoulders and wrists in one line. Then, extend one leg out and stretch out the opposite arm, as shown in the picture. Return to start and switch arms and legs.

Erector spinae, first position

Erector spinae, second position

Jennifer Cohen is a leading fitness authority, TV personality, best-selling author, and entrepreneur. With her signature, straight-talking approach to wellness, Jennifer was the featured trainer on The CW’s Shedding for the Wedding, mentoring the contestants’ to lose hundreds of pounds before their big day, and she appears regularly on NBC’s Today Show, Extra, The Doctors and Good Morning America. Connect with Jennifer on Facebook, Twitter, G+ and on Pinterest.