Body Muscles: Anatomy and Strengh training Basics

Have you ever wondered how many muscles there are in the human body? The answer to this question actually depends on the type of muscle we are talking about. But in general, one naturally thinks of skeletal muscles of the body, i.e. those which generate the movements.

It is estimated at over 650 the muscles of the body acting on the skeleton. Other muscle tissue, such as smooth muscle, typically occurs at the cellular level, which means you can actually have billions of smooth muscle cells.

All the muscles of the body perform various vital functions. This of course includes the movements of the body, but also the transit of food through your digestive tract and the work of the heart to pump blood.

Would you like to know more about your dynamic muscular system? Read on to learn about the different types of muscles, their various functions, and more.

The different types of muscles in the human body

Your body has three different types of muscles.

They understand :

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1. Skeletal muscles

Also called striated muscles, they are usually attached to your bones at the joints by tendons. Each of them is made up of thousands of muscle fibers grouped together.

The organized arrangement of their muscle fiber leads to a striped or ridged pattern, hence the name striated muscle.

A skeletal muscle is primarily involved in movement. When it contracts, it allows movement of a specific area of the body.

Your skeletal muscles are volunteers, meaning you can control their movement. This is the only category of muscles for which this is possible. The others work without asking you for anything 😉

2. Cardiac muscle

As the name suggests, cardiac muscle is only found in your heart to generate its beats. It is also called myocardium.

The myocardium is one of the 3 layers of tissue in your heart, located between the inner lining of the heart (endocardium) and the protective sac that surrounds your heart (pericardium).

Similar to skeletal muscle, cardiac muscle has a striped appearance. Individual heart muscle cells are tightly linked to each other, allowing your heart to beat in a coordinated fashion.

Like smooth muscle, cardiac muscle is involuntary. It contracts in response to electrical impulses generated by specific cells located in the right atrium. They are grouped together in what is called the sinus node.

The electrical signal travels from the upper to the lower part of your heart. Because heart muscle cells are tightly bound to each other, they are able to contract in a coordinated wave-like fashion that forms the heartbeat.

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3. Smooth muscles

Unlike the 2 previous types of muscles, these do not have a direct link with physical exercise. However, it's always good to grow a little, and since we're talking about the muscles of the body...

Smooth muscles can be found in these different body systems, among others:

  • digestive
  • respiratory
  • cardiovascular
  • renal
  • reproductive
  • ocular (expansion or contraction of the pupils)

Smooth muscle cells are often rounded in the center and tapered at the sides. Unlike skeletal muscles, they are not not streaked. Their name refers to the more uniform appearance of this type of muscle tissue.

Smooth muscle is involuntary, meaning you can't control its movement. Each cell contains chains of filaments that can connect it to other nearby cells, forming a mesh-like network that allows cells to contract evenly.

Well, you will have understood it, it will be very difficult for you to build them with a conscious effort 😅

Our other articles on body muscles

Before we go any further, here are some other articles that may interest you to learn more about muscles:

Skeletal muscles

These are the ones you are most interested in while playing sports. These are the ones you can control and develop.

The functions of your skeletal muscles include:

  • move the body
  • Provide structural support
  • maintain posture
  • Generate heat to maintain body temperature
  • Act as a source of nutrients such as amino acids
  • Serve as a source of energy when you haven't eaten enough

Skeletal muscles can be divided according to the area of the body they serve, such as:

Head and neck muscles

Muscles of the body - head and neck

The muscles in this area control the movements of the face, head and neck. Examples include:

Zygomatics (large and small): These are probably the best known of the muscles of the face. The zygomaticus major is involved in facial expression and lifts the corners of your mouth, like when you smile. The small zygomatic will make you look rather sad by pulling the upper lip backwards. The 2 play a important role in chewing.

Masseter: It is found in the jawbone and is used to close the mouth and chew food.

Extraocular muscles: This is a group of muscles that control your eye movements as well as the opening and closing of your eyelids.

Tongue muscles: This muscle group helps to raise and lower the tongue as well as help it move in and out.

Levator scapula muscle (or scapula): the NASM classifies it in the muscles of the neck where it is actually located, while others rank it in those of the shoulder because of its action on the scapula (elevation). However, it also stabilizes the cervical vertebrae.

Sternocleidomastoid: This is the main muscle that is involved when you rotate or tilt your head to the side. It also participates in tilting the head forward. In fact, it's the one you can really develop in bodybuilding, although the levators of the scapula, the masseter and the zygomatics work during intense efforts and develop. 

Other deep neck muscles are the scalenes anterior, middle and posterior as well as the longus neck muscle.

Muscle gain with elastics

Shoulder muscles

Shoulder and pectoral muscles

These are the muscles that provide the connection between the bust and the arms. They work around the most complex and fragile joint in the human body. They must therefore be developed with care, contrary to what is often done (and I paid the price).

Here are examples of important muscles in this area:

Serratus anterior muscle (serratus anterior): It is a deep muscle composed of 3 bundles which provide abduction and stabilization of the shoulder blades.

Trapeze: This muscle is made up of 3 bundles (upper, middle and lower) that go from the neck to the middle of the back. It is solicited in several movements, in particular tilting the head back, raising the shoulders and bringing the shoulder blades together.

Deltoid: It is the most powerful of the shoulder and the one that gives it its rounded shape. Triangular in shape seen from above, it is located on the outer face of the shoulder. It is divided into 3 bundles: anterior or clavicular, middle or acromial, posterior or spinal. It works especially during the lateral or frontal elevations of the arms.

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Great circle (teres major): Hanging on the lower angle of the scapula to go up to the anterior face of the humerus, it performs a movement of adduction and rotation towards the back of the shoulder.

Greater rhomboid: Flattened and wide back muscle below the trapezius. The rhomboids control the movement of the scapula and the cervical spine. They also participate in the elevation of the shoulders and are antagonistic to the serratus anterior.

Small rhomboid: thin muscle covered by the trapezius and located just above the rhomboid major.

Rotator cuff

Although located at the level of the shoulders, it is necessary to put these muscles a little apart. Indeed, these are the 4 muscles that attach to the head of the humerus and cover it like a headdress.

They allow the head of the humerus to remain centered in front of the glenoid bone of the scapula, the area covered with cartilage. They also participate in rotational movements of the shoulder.

Small circle (teres minor): It pulls and stabilizes the humeral head in the glenoid fossa. It is the external rotator of the arm and the adductor (brings the arm closer to the axis of the body).

Infraspinatus (infraspinatus): Located under the spine of the scapula, this muscle ensures the external rotation of the arm.

Subscapular or Subscapular: This muscle is deep, wide, flat and triangular in shape. It ensures the internal rotation of the humerus.

Supra spinatus (supraspinatus): It is placed above the spine of the scapula and ensures the first degrees of abduction of the arm (elevation up to 15°). It also participates in the stabilization of the glenohumeral joint.

The pectorals

There are many moves that involve the front of the shoulders along with the pecs. Forgetting this important point often produces rotator cuff (subscapularis) injuries.

Pectoralis major (pectoralis major): This bodybuilding fan favorite is located in your upper chest and is used for rotational, vertical and lateral movements of your arm.

Small pectoral (pectoralis minor): Triangular in shape, this muscle, also called minor pectoral, belongs to the deep plane of the anterior compartment of the shoulder. It is located under the pectoralis major.

Arm muscles

Triceps brachii: Its 3 bundles are the long portion, the vastus medialis and the vastus lateralis. This posterior muscle extends the forearm by straightening the elbow. It represents the largest volume of the arm.

Biceps brachii: This superficial muscle is located at the front of the arm. Its 2 heads are the long head and the short head. He flexes his forearm by bending his elbow.

Anterior brachialis: It is one of the 2 deep muscles located under what are commonly called the biceps. It participates in the flexion of the elbow and contributes to the anterior volume of the arms (do not neglect it in your sessions).

Forearm

The forearm has twenty muscles, divided into three compartments, anterior, posterior and lateral. I'm not going to detail them all, except for the brachioradialis which is important in bodybuilding. The others work naturally in all exercises involving grip.

The anterior compartment (or anteromedial) has 8 muscles. The superficial plane is composed of the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi superficial, and flexor carpi ulnaris. The deep plane is made up of the flexor digitorum profundus, flexor pollicis longus and quadratus pronator muscles.

The posterior compartment also has 8 muscles. The superficial plane is composed of the extensor digitorum, extensor digitorum longus, extensor carpi ulnaris, and anconeus muscles. The deep plane is made up of the abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, and extensor digitorum index muscles.

The side lodge has 4 muscles: brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis and supinator.

Brachioradialis: Formerly called long supinator, it is a superficial muscle of the radial region of the forearm which also participates in the flexion of the elbow with the 2 previous ones. It also brings the forearm back to a neutral pronation-supination position.

Dorsal muscles

The rhomboids are sometimes classified among the muscles of the back. However, given their important action on the shoulder blades and shoulder elevations, many specialists classify them among the skeletal muscles of the shoulders (see above).

Erector spinae muscles: It is a group of 3 muscles divided into several bundles allowing the extension of the vertebral column or rachis: the ilio-costalis, longissimus and thorny. They are extremely important for posture.

Loin square (quadratus lumborum): It is a quadrilateral muscle, wider below than above, of the posterior region of the abdomen close to the lumbar region. Among other things, it plays an important role in stabilizing the lower spine during walking.

Transverse-spinatus: It is a group of 3 muscles made up of the multifid (multifidus), of semi prickly and rotators (short and long). They play a role in tilting, rotating, extending and stabilizing the spine.

Latissimus dorsi (latissimus dorsi): It is a large, triangular-shaped muscle that is part of both the back and the shoulder. All athletes love this muscle which gives the bust its V-shape, very visible in swimmers for example. It is used for adduction and internal rotation of the arm as well as elevation of the pelvis.

>> Read the full article on back muscles <<

Abdominal muscles

Ab muscles

They are located in your abdomen area. Some are superficial muscles while others are deep muscles. They all play a major role in the sheer strength of an individual. You can't be strong without a good core.

This muscle group includes:

Rectus muscle (formerly rectus abdominis): The person responsible for the famous chocolate bars… when the fat is gone. It is the main muscle of the abdominal wall. It is polygastric, in other words in several parts, and wider at the top than at the bottom. It is extremely resistant, which explains why athletes are able to train it every day.

Internal and external oblique muscle: This muscle group helps you bend to the side or rotate at the waist.

Internal and external intercostals: As their name suggests, they are located between your ribs and facilitate inspiration (external intercostals) and expiration (internal intercostals). Their tearing can hurt a lot.

Diaphragm: The diaphragm separates your torso from your abdomen. It is also involved in breathing, contracting when you inhale and relaxing when you exhale.

Hips and buttocks

Short adductor (adductor brevis): Triangular muscle belonging to the intermediate plane of the medial compartment of the thigh. It is located just above the adductor longus.

Long adductor (adductor longus): Superficial triangular skeletal muscle located in the inner part of the thigh. In sports, his tears are quite common in football or handball.

Great adductor (adductor magnus): Belonging to the inner compartment of the thigh, it is a muscle composed of 3 bundles (upper, middle and lower).

Gracilis (gracilis): Long, thin muscle belonging to the medial compartment of the thigh. It is flattened and extends from the pubis to the tibia along the inner edge of the thigh.

Pectineus (pectineus): It is a short muscle located above the adductor brevis. Like the following, it generates adduction or approximation and flexion of the hip.

Gluteus minimus or gluteus minimus (gluteus minimus): It is the deepest of the buttock muscles. It belongs more precisely to the dorsal and lateral muscles of the shoulder girdle which connect the lower limbs to the trunk.

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Gluteus medius or gluteus medius (gluteus medius): Located just above the gluteus maximus and below the gluteus maximus, this muscle performs the same functions.

Gluteus maximus or gluteus maximus (gluteus maximus): This superficial muscle is the erector of the trunk. It is solicited for the movement of your hips and thighs. It is important for stabilizing the pelvis, maintaining posture, getting up from a seated position or climbing stairs. 

Tensor fascia latae (tensor fascia latae): It belongs to the lateral muscles of the pelvic belt, which attach the lower limbs to the trunk on the outer side of the buttock.

Ilio-psoas (formerly iliopsoas): It is made up of two heads or main bundles which are the psoas major (psoas major), stretched between the lumbar spine and the upper end of the femur, and the iliac muscle (iliacus) which extends from the iliac fossa to the the upper end of the femur.

Sartorius or couturier muscle: It is the longest in the human body, located along the inner thigh and S-shaped.

Piriformis (piriformis): A deep pear-shaped muscle (hence its name) that connects the pelvis to the thigh. It is often the cause of pain related to sitting or lying on the side.

Quadriceps

Quadriceps muscles

It's actually a group of 4 muscles (hence the name) located at the front of your thigh and working together to straighten your leg at the knee.

These muscles are:

Vastus lateralis (vastus lateralis): Located on the outer side of the thigh, it generally works with all of the quadriceps. Contracted alone, it shifts the patella upwards and outwards.

Vastus intermedius (vastus intermedius): Also called crural muscle, it is apparent in the central part of the upper thigh. It is made of short and very dense fibers.

Vastus medialis or vastus medialis (vastus medialis): It is located on the inner side of the thigh. It is quite noticeable above the knee when the leg is extended in contraction, such as at the end of a sissy squat or on a leg press.

Rectus femoris muscle (rectus femoris): Quite long, it allows the extension of the leg and the flexion of the thigh on the pelvis.

Hamstrings

This muscle group at the back of the thigh helps extend your thigh and bend your leg at the knee.

He understands :

Biceps femoris (biceps femoris): Formerly called biceps crural, it consists of a long head and a short head. Its contraction causes the knee to flex and the hip to extend. It also causes external rotation of the tibia.

Semitendinosus (semitendinosus): It is a central superficial muscle at the back of the thigh. It is knee flexor, medial knee rotator, hip extensor and pelvis retroversor.

Semi-membranous (semimembranosus): It is a deep muscle located under the semi-tendinosus participating in the flexion of the knee and its internal rotation. It also helps in hip extension.

>> Read the full article on thigh muscles <<

Legs (calves)

Leg or calf muscles

They are often called calves or lower legs because we are used to calling all of the lower limbs legs in everyday language. But in anatomy, the leg represents the part of the body that goes from the knee to the ankle, the area of the tibia and the fibula.

Anterior tibial (anterior tibialis): You use this muscle when you lift the sole of your foot off the ground. It is the flexor of the foot on the leg (dorsiflexion), adductor and supinator.

Posterior tibialis (posterior tibialis): Formerly called the tibialis posterior muscle, it is located at the back of the tibia. It is essentially an extensor of the talocrural joint, and secondarily internal rotator and adductor.

Soleus (Soleus): This deep skeletal muscle is inseparable from the gastrocnemius since with the latter they make up the triceps surae. Indeed, their different bundles come together to form the calcaneal tendon or Achilles tendon. The soleus is above all an extensor of the foot (plantar flexor), which stabilizes the leg on the foot when standing.

Gastrocnemius muscle or twin muscles (gastrocnemius): Located on the surface of the soleus with which it forms the triceps sural, it is composed of 2 heads or bundles. This is what is commonly called the calf because it gives it its curved shape. It is primarily responsible for the propulsive force during walking or running.

Peroneus longus (peroneus longus): Formerly called the peroneus longus lateral, it is a muscle located on the outer side of the leg. It consists of 3 beams. It is a plantar flexor of the foot on the leg, abductor and lateral rotator of the foot. It especially supports the outer arch of the arch of the foot.

>> Read the full article on calf muscles <<

Composition of muscles

Striated skeletal, smooth or cardiac muscles have very different functions, but they share the same basic composition. A muscle is made up of thousands of tightly packed elastic fibers. Each packet is wrapped in a thin transparent membrane called perimysium.

An individual muscle fiber is made up of blocks of protein called myofibrils, which contain a specialized protein (myoglobin) and molecules to provide the oxygen and energy needed for muscle contraction.

Each myofibril contains filaments which fold when they receive the signal to contract. This reduces the length of the muscle fiber which, in turn, shortens the entire muscle when enough fibers are stimulated at the same time.

Let's focus now on the skeletal muscles since these are the ones that particularly interest us in the practice of sport...

Functions of the muscles of the human body

To move the skeleton, the tension created by the contraction of the fibers of most skeletal muscles is transferred to the tendons. Tendons are strong bands of dense, regular connective tissue that connect muscles to bones.

This bony connection is why this muscle tissue is called skeletal muscle. 

Skeletal muscle interactions

To pull on a bone, i.e. to change the angle of its synovial joint (or diarthrosis), a skeletal muscle must also be attached to a fixed part of the skeleton.

the point of origin is the point of attachment to the bone that remains fixed. the insertion point is the point of attachment of the muscle to the bone which it sets in motion.

Agonist and antagonist muscle

Although any number of muscles can be involved in an action, the main muscle involved is called the prime mover, or agonist. To do a bicep curl, the biceps brachii is actually the agonist.

However, as it can be assisted by the brachialis anterior, the latter is called synergist in this action. It can also be a fixator that stabilizes the bone of the prime mover point of origin.

A muscle opposing the agonist is called antagonist. Antagonists play 2 important roles in muscle function:

  • They maintain the position of the body or limbs;
  • They control the speed of movement.

For example, to extend the knee, all 4 quadriceps muscles are activated (and are then the agonists of knee extension). However, to flex the knee joint, a set of opposing or antagonistic muscles called the hamstrings are activated.

As you can see, these terms would be reversed for the opposite action. If you think of the first action as knee flexion, then the hamstrings will be called the agonists and the quadriceps femoris will then be called the antagonist.

Some exceptions

There are also certain skeletal muscles that do not pull on bones for movement.

For example, the insertions and origins of facial muscles are in the skin, so that certain individual muscles contract to form a smile or a frown, to form sounds or words for example.

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For its part, the diaphragm contracts and relaxes to modify the volume of the pleural cavities, but it does not move the skeleton to do so.

The neuromuscular system

The brain, nerves and skeletal muscles work together to cause movement. This is collectively known as the neuromuscular system. A muscle is often served by 50 to 200 (or more) branches of movement-specialized nerve cells called motor neurons or motor neurons.

These connect directly into skeletal muscle. The end of each branch is called the presynaptic terminal. The point of contact between the presynaptic terminal and the muscle is called the neuromuscular junction.

To move a particular body part, these 3 things happen:

  1. The brain sends a message to the motor neurons;
  2. This triggers the release of the chemical acetylcholine from the presynaptic terminals;
  3. The muscle reacts to acetylcholine by contracting.

NOTE : It is precisely the unexplained degeneration of motor neurons that causes amyotrophic lateral sclerosis (ALS), also known as Charcot's disease.

Muscle fiber differences

body muscles and exercise

Skeletal muscles are made up of individual muscle fibers of which there are 2 types: fast twitch and slow twitch. They each have different functions that is important to understand when it comes to programming movements and exercises.

Slow twitch muscle fibers

They are fatigue resistant and focus on sustained, smaller movements. They are also essential for controlling posture.

These slow fibers contain more mitochondria and myoglobin, but little glycogen. They are aerobic in nature compared to fast twitch fibers. They are also sometimes called type I fibers or red fibers because of their blood supply.

Fast twitch muscle fibers

These provide more strength and power, but for shorter durations with rapid fatigue. They are more anaerobic with less blood supply, which is why they are also called white fibers or type II.

Skeletal muscle contains both types of fibers, but the ratios can vary depending on a variety of factors, including muscle function, age, training, and heredity.

Body muscles and exercise

Before exercising, it is important to warm up the muscles, tendons and joints.

Benefit of warming up and stretching

Stretching pulls muscle fibers and also causes increased blood flow to the muscles you are going to work.

Without a proper warm-up, it is possible to damage certain muscle fibers or stretch a tendon that is still cold. This can lead to pain, swelling, and decreased function. If moderate to severe, this injury can immobilize you for some time.

NOTE : Stretch before a session, but especially not after because the micro tears created in the muscles during the effort can turn into tears.

Warming up for the joints

Keep in mind that muscles act on joints to create movement. Most of the joints you use during exercise are synovial joints. They contain synovial fluid in the joint space between two bones.

Warm-up exercises and stretching can also have a beneficial effect on the joints. Synovial fluid is a thin but viscous film having the consistency of egg white. When you get up and start moving, your joints feel stiff for a number of reasons.

After proper stretching and warming up, synovial fluid is less viscous, allowing for better joint function.

Muscular disorders

Muscle disorders can cause weakness, pain, loss of movement, and even paralysis. The set of problems that affect the muscles are collectively known as myopathy.

Common muscle problems include:

  • Injury or overuse, including sprains or strains, cramps, tendonitis and bruises;
  • Genetic problems, such as muscular dystrophy;
  • Inflammation, such as myositis;
  • Nerve diseases that affect the muscles, such as multiple sclerosis;
  • Conditions that cause muscle weakness, such as metabolic, endocrine, or toxic disorders. This is the case, for example, of diseases affecting the thyroid and adrenal glands, myasthenia gravis, alcoholism, pesticide poisoning, use of certain medications (steroids, statins, etc.) ;
  • Cancers, such as soft tissue sarcoma.

Other interesting details about the muscles of the body

Effect of sarcopenia on muscles
The effect of sarcopenia on the muscles of the body

Want to learn even more about your muscles?

Here are some other facts to know:

  • Your skeletal muscles make up between 40 and 50 % of your total body weight.
  • Skeletal muscle mass begins to decline with age in a phenomenon called sarcopenia. This process usually starts after the age of 40 and accelerates after 50. I'm right in it 😪
  • Water is important to all living things and your muscles are made up of approximately 79 % of water.
  • The largest muscle in your body is the gluteus maximus. However, having big buttocks does not necessarily mean that they are very muscular 😂
  • Eye muscles perform about 10,000 coordinated movements in just 1 hour of reading. Reading is the most demanding sport at the muscular level 😉 Think about it the next time you open a good book...
  • Your heart muscle works very hard and has limited regenerative abilities. This is why damage to this tissue by diseases such as heart disease or myocarditis can have serious consequences. A healthy heart pumps over 8000 liters of blood in a single day. 
  • Smooth muscle tissue is important for moving food through your digestive tract. Did you know that it takes about 44 hours for the food you eat to pass through your digestive tract?
  • Although we don't often think about it, smooth muscle is vital. Indeed, many treatments target this tissue. Examples include drugs to treat asthma and high blood pressure.

Body Muscles: Conclusion

Muscle tissue is found throughout your body and its structure and function can be very diverse. 

Your muscles perform many important functions that are essential to your health. Some examples of processes that muscles are involved in include things like movement, digestion, and your heartbeat.

You have 3 different muscle types: skeletal, smooth, and cardiac. There are over 650 skeletal muscles. This article has basically introduced you to the list of body muscles that bodybuilding targets. Apart from those of the face, of course...

Step by step, this section will introduce you to the most important muscle groups so that you can work them well at home. So do not hesitate to come back regularly to this blog.

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Related words: small muscle union of muscles mandibular nerve oculomotor nerve sterno-hyoid muscle pterygoid muscle dorsal scapular nerve anterior muscles scalene muscles stapedius muscle palatoglossus muscle palatopharyngeus muscle blood vessels contractile tissues level of muscle fibers

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