Muscle and Function: Deltoid Muscle
The deltoid is a triangular shaped muscle at the top of your shoulder. It plays a major role in moving and stabilizing your shoulder joint. The major movements the deltoid muscle is responsible for are arm rotation, arm flexion, as well as moving your arm towards and away from your body (adduction and abduction). It also helps you pull your arms behind your body. Think about when you are carrying a box out in front of you or lifting something over your head. The deltoid muscle helps you perform these activities.
Origin and Insertion
Most people think of the deltoid as one big muscle in their shoulder. However, they do not 
realize that the deltoid muscle is made up of three parts: the anterior deltoid, the medial deltoid and the posterior deltoid. The anterior deltoid has its origin in the collar bone. It is the part of the deltoid that helps with arm adduction, arm flexion, and rotating your arm inward.The middle deltoid has its origin in the shoulder blade. It is primarily responsible for arm abduction. The posterior deltoid also originates in the shoulder blade and is responsible for extending your arm behind your body, as well as lateral rotation. All three parts insert at the deltoid tuberosity of the humerus, which is the long bone of your upper arm.
Exercises for the Deltoid
Strong deltoids are crucial in order to carry out everyday activities, such as carrying objects, and can help prevent injuries such as torn rotator cuffs. It is important when exercising to strengthen all three parts of the deltoid. People commonly focus on the anterior deltoids because it is what they see when they look at their shoulder. However, it is crucial not to neglect the middle and posterior deltoid. Exercises to strengthen your deltoid include the shoulder press, front raise, lateral raise, and the upright row. The shoulder press and front raise work your anterior deltoid. The lateral raise works the middle deltoid, and the upright row works the posterior deltoid. At Vertex, exercises are carefully planned to target all three parts of the deltoid in order to maximize shoulder strength.
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About the author
Dwayne Wimmer founded Vertex Fitness Personal Training Studio in 2001, excited to bring a new concept about personal training to the people of Philadelphia’s Main Line in Pennsylvania. Driven by knowledge and results both, while a strength coach at Villanova University, he worked closely with world class athletes such as Brian Westbrook, formerly of the Philadelphia Eagles, on strength training and conditioning for optimal performance. Dwayne’s client base extends much further than world class athletes. Along with athletes, he works with adolescents to seniors, and he’s a highly acclaimed and sought out personal trainer who has received numerous awards, such as Best of the Main Line Personal Training Studio and Best Main Line Personal Trainer. A graduate of Missouri Western State University, Dwayne has a Bachelor of Science degree in Physical Education, with an emphasis in Coaching. Aside from personal training, he’s spent time as a physical education teacher, strength and conditioning coach, and a football coach, but has found his passion and home in the fitness industry, inspiring and reaching out to others. As a strong believer in continuing to learn, Dwayne has also taken classes at East Stroudsburg University toward a Masters Degree in Sports Management. He can add author to his list of accomplishments, having created a chapter in the upcoming book The Soul of Success with Jack Canfield, renowned for the Chicken Soup series. To get to the point where he is now, Dwayne has always been thankful for the support of his father, a man who always believed in his mission and saw the need for what it was that Dwayne envisioned. During his free time, Dwayne is an avid motorcyclist who enjoys viewing the amazing landscapes and finding good restaurants to enjoy that are off the beaten path. He also takes advantage of opportunities to travel and experience many other cities while attending fitness seminars and giving presentations about the industry he is so passionate about. As a way to give back to the community that has been a part of his entire life, Dwayne has created Vertex Fitness PUMPED (People United Making Progress through Education and Donations), which provides support to area non-profits through a community-wide outreach effort. At this time, they help three non-profits per year in the Philadelphia area. For more information from Dwayne, you may contact him at (610) 525-6604, dwayne@vertexfit.com