HBS 4.2.2

Objectives You will understand how muscle insertion and origin relate to the function of the muscle. You will be able to Model the muscles of the chest Explain to a client exercises that will strengthen those muscles.

As you go through this activity Add the muscles that you built to your data table – with the origin, insertion and movement.

Intro Ready to make a change and get fit, Jim Strong decides to join a gym. He has been working out on his own for a few weeks, but he is not seeing the results he had anticipated. Now he is coming to you, a personal trainer, for advice. You sit down to discuss a training plan with Jim and you quickly see that he has some major misconceptions about muscle anatomy. Jim is a busy man and he wants to get the most out of a quick workout. He only wants to work in one exercise to tone and build his chest. “It’s one big muscle, right? Shouldn’t one exercise do the trick?” Your job is going to be tougher than you thought.  

Intro continued In this activity, you will explore the anatomy of the human chest and build this series of muscles on your Maniken®. Your finished product will help you show Jim the structure of the chest as well as explain how each muscle component controls a different motion (and thus requires a variety of different toning exercises). Each muscle has a set of unique attachments on the body and this structure directly links the muscle to the action it controls. Demonstrate the action of each muscle and show Jim why one exercise is never going to get him the results he desires. Once you learn the function of each muscle of the chest, research and suggest exercises that will target the areas Jim is looking to tone.

For each muscle Name of the muscle Location of the origin and the insertion of the muscle The action of the muscle A sport or activity that utilizes this muscle

Muscle #1: Intercostals Build the external intercostals of the chest. These muscles are found in between the ribs and extend from the front of the ribs, around back and past the bend in the bones.   What is the function of these muscles?

Muscle #1: Intercostals Have you ever eaten ribs? Actually eating the intercostal muscles between the bones, not the ribs themselves.

Muscle #1: Intercostals Place a strand of spaghetti between each rib, starting at the back of the rib where it attaches to the vertebral column, all the way around to the rib’s attachment at the sternum. Use your thumb or one of the clay tools to flatten down these strands. The intercostal muscles do not stick out of the chest.

Muscle #2 – Serratus Anterior Use this website to help you find insertion and origin: http://www.getbodysmart.com/ap/muscularsystem/shouldermuscles/anteriormuscles/serratusanterior/tutorial.html

Muscle #2 – Serratus Anterior We would have to take off the arm, so let’s fake it… Origin = lateral surface of ribs 1-8 (bone only) Insertion = medial border of the scapula Note that this muscle helps move the scapula forward and is often used at the end of big movements such as a bench press, a baseball pitch, or a swimming stroke.

Muscle #3- Pectoralis Minor Origin = anterior surface of ribs 3 – 5 (just past the origins of the serratus anterior) Insertion = coracoid process of the scapula (piece of the scapula visible on the front)

Muscle #3- Pectoralis Minor Use spaghetti strands to form the pectoralis minor. Place one small strand at the origin of each rib and run these three strands together as they attach at the scapula. The muscle is built in a manner similar to the serratus anterior

Muscle #3- Pectoralis Minor Act out the movement of this muscle. This muscle works to rotate the shoulder forward.

Muscle #4 – Pectoralis Major Even though this muscle only has one name, there are actually three different “heads” or pieces to this muscle. Each part will be built separately and will be formed from a carrot-shaped tube that has been rolled flat. Keep these muscles thick and striate each muscle as it is built.

Muscle #4 – Pectoralis Major First construct the abdominal head of the pectoralis major. Given the name only, where do you think this muscle might attach?   Origin = ribs 5-7 (actually attaches to fascia of abdominal muscles) Insertion = lateral edge of the most proximal part of the humerus

Muscle #4 – Pectoralis Major Make a long carrot out of terra cotta clay. Flatten the carrot slightly to make a tongue. Gently lay the muscle across the chest of the Maniken® from the origin to the insertion. The long end of the carrot should point towards the shoulder and the wide end should run down towards the 5th through 7th rib. The muscle will have a teardrop shape. Keep the insertion very narrow and the origin much wider. Do not worry about perfect shape at this point. You will trim the muscle to fit the Maniken®.   Use the wire tool or a pencil to carefully outline the shape of the muscle and trim off any jagged edges

Muscle #4 – Pectoralis Major Take the muscle off the model and use the knife to trim the edges you have marked with your tool or pencil. Gently roll out the muscle if you need to stretch it a bit to fit from the origin to the attachment. Attach the muscle to the model. Striate the muscle. Remember that the striations of the muscle indicate the direction the muscle moves.

Muscle #4 – Pectoralis Major Act out the motion of this portion of the pectoralis major. Describe which sports or exercises utilize this muscle. You may relate this muscle action to the last part of a tennis serve or a volleyball spike. You may have seen the pull-down pulley system in the gym that allows a person to isolate and train this portion of the muscle.

Muscle #4 – Pectoralis Major Now create the largest portion of the muscle – the sternal or sternocostalis head. Given the name only, where do you think this muscle might attach? Origin = ribs 1-5 on the lateral edge of the sternum (no clay should be on the sternum) Insertion = lateral edge of the humerus, inferior to the insertion of the abdominal head.

Muscle #4 – Pectoralis Major Make a short, fat carrot out of terra cotta clay. Flatten the carrot slightly to make a thick triangle. Do not worry about perfect shape at this point. You will trim the muscle to fit the Maniken®.  Gently lay the muscle across the chest of the model from the origin to the insertion. The long end of the carrot should point towards the humerus and the wide end should run along the lateral edge of the sternum. The origin of this muscle will overlap the origin of the abdominal head.

Muscle #4 – Pectoralis Major Use the wire tool or a pencil to carefully outline the shape of the muscle.  Take the muscle off of the model and use the knife to trim the edges you have marked with your tool or pencil. Gently roll out the muscle if you need to stretch it a bit to fit from the origin to the attachment. Make sure no clay extends over the sternum. Attach the muscle to the Maniken®. Ask students to striate the muscle. Remember that the striations of the muscle indicate the direction it moves.  

Muscle #4 – Pectoralis Major Act out the motion of this portion of the pectoralis major. Brainstorm which sports or exercises utilize this muscle. This muscle adducts the arm across the chest and is at the route of a tennis forehand shot. You may reference the butterfly machine in the gym that allows a person to isolate and train this portion of the muscle.

Muscle #4 – Pectoralis Major Create the smallest portion of the muscle – the clavicular head. Given the name only, where do you think this muscle might attach? Origin = medial half of inferior edge of the clavicle Insertion = lateral edge of the proximal humerus, inferior to the insertion of the sternal head.

Muscle #4 – Pectoralis Major Create the smallest portion of the muscle – the clavicular head. Given the name only, where do you think this muscle might attach? Origin = medial half of inferior edge of the clavicle Insertion = lateral edge of the proximal humerus, inferior to the insertion of the sternal head.

Muscle #4 – Pectoralis Major Make a small carrot out of terra cotta clay. Flatten the carrot slightly to make a shape similar to an isosceles triangle. Do not worry about perfect shape at this point. You will trim the muscle to fit the Maniken®.  Gently lay the muscle across the chest of the model from the origin to the insertion. The long end of the carrot should point towards the humerus and the slightly wider end should run up against the bottom of the clavicle. The insertion of this muscle will cross over the insertion of the other two muscles on its way to the humeral attachment.

Muscle #4 – Pectoralis Major Use the wire tool or a pencil to carefully outline the shape of the muscle. Take the muscle off the model and use the knife to trim the edges you have marked with your tool or pencil. Gently roll out the muscle if you need to stretch it a bit to fit from the origin to the attachment. Remember to striate… in the right direction!

Muscle #4 – Pectoralis Major Act out the motion of this portion of the pectoralis major. Describe which sports or exercises utilize this muscle. This muscle is responsible for underhand motions such as bowling or throwing an uppercut in boxing. You may reference a pulley system in the gym that allows a person to pull upward and isolate this muscle.

Do this… Sketch the muscles you have built on your muscular system graphic organizer. Reference the muscle atlases or anatomical drawings on the Internet for ideas on how to draw the muscles. You do not need to be a medical illustrator. Draw the muscle in a way that makes sense to you. Number each muscle. Next to the number, write the name of the muscle and briefly describe the action of the muscle. Alternatively, you can create a key on a separate sheet of paper.

Success Check – Due Thursday!  Look at your Maniken®. Explain to your client why you need multiple exercises to effectively build and tone the muscles of the chest.