To make sure your resistance training is both effective and safe, you should be aware of which muscles correspond with what body parts. Consult the following images and read the descriptions of each part of the body.

Shoulders

Deltoids are the muscles that run over the tops of your arms. They are responsible for moving your upper arm in many directions.

The rotator cuff is a group of four muscles underneath your shoulder. They are used for throwing and catching, carrying, and reaching.

Back

The trapezius is the elongated diamond-shaped muscle that runs from your neck, across your shoulders, and down to the center of your back. It is used for most back functions, as well as lifting your arms out sideways to wave to someone.

The latissimus dorsi is the largest of your back muscles, and it goes from below your shoulders to your lower back. It is used for pulling. Strong lats help make sure your shoulders don't round forward.

Rhomboids are small, rhomboid-shaped (similar to rectangles) muscles underneath the trapezius at the center of your back. They are used to keep your shoulder blades together, which helps your posture.

Erector spinae muscles run the length of your spine, but you want to emphasize strengthening the lower segment of this muscle. All the spinae enable you to straighten your spine, to go from reclining or bending, and to stand or straighten your body.

Chest

Pectoralis are the main muscles of your chest. And yes, even if you have breasts, you have pectoralis muscles underneath. Activities that require you to push with your arms happen because of your pecs. They help to push a wheelchair, shopping cart, or lawn mower.

Upper Arm

Biceps are the two most famous muscles at the front of your arm. Any time you bend your elbow, you engage your biceps (e.g., when carrying small children or pets, and when lifting groceries).

Triceps are the three-headed muscles opposite of your biceps, on the back of the upper arm. They straighten your elbow and help out your pecs when you push something.

Forearm

There are many forearm muscles with too many names to mention here; think of them as your wrist muscles. Developing these helps prevent or alleviate symptoms of carpal tunnel syndrome and tennis elbow.

Abdominals

This set of four muscles allows you to bend at your waist, twist, and keep your torso stable. The abdominals (abs) and back muscles are neighbors, and when strong, they support your posture and back.

Rectus abdominis are the long, running muscles that start under your chest and end below your umbilicus (otherwise known as your navel or belly button).

Internal and external obliques run obliquely or diagonally down the sides of your rectus abdominus. These enable you to twist or bend at your side.

Transversus abdominis are the deepest of the four abdominal muscles. The transversus abdominis comes along for the ride when you exercise the other ab muscles. It is most active when you sneeze, cough, or exhale deeply.

Buttocks and Hips

Gluteus maximus, medius, and minimus are the largest muscles on your body. They are involved in nearly everything you do with your lower body, including walking, running, stepping, jumping, and getting up.

Legs

Quadriceps are the group of four muscles on the front of your thigh. These allow you to straighten your leg at the knee.

Hamstrings are the group of three muscles on the back of your thigh. These allow you to bend your leg at the knee.

Gastrocnemius and soleus are better known as your calf muscles. The gastroc is the rounded muscle at the back of your lower leg, and the soleus is just underneath. Women who wear high-heeled shoes may have some calf development (and chronic soreness) because the constant angled position of the foot causes these muscles to contract or tighten.

Tibialis anterior (shins) are on the front of your lower leg and go from just below your kneecap to the top of your ankles. These muscles allow you to extend or point your toes. They work in opposition to the calf muscles, so you want to keep them balanced.