Table of Contents

Functional Anatomy of the Human Body

Traditionally, training focused on specific body parts, often in single, fixed planes of motion. Similarly, anatomy has been taught in isolated and fragmented components. This approach provided simplistic answers about the structures, categorized each component, and mapped the body. However, the human body functions as an integrated and multidimensional system, not a series of isolated, independent pieces. Therefore, the new approach is to present anatomy from a functional and integrated perspective.

Muscles have the ability to dominate a certain plane of motion, but the central nervous system (CNS) optimizes the selection of muscle synergies instead of individual muscles. The CNS coordinates deceleration, stabilization, and acceleration for all muscles of the body in all three planes of motion. Additionally, muscles must react to external stimuli such as gravity, momentum, ground reaction forces, and forces created by other functioning muscles. Therefore, muscles can switch up the role they play like actors in a movie, based on the load, direction of resistance, body position, and the movement pattern being performed. There are four movement production roles that muscles can dynamically take on, depending on these factors. These roles include the following:

Agonist: In terms of movement, a muscle is considered an agonist when it serves as the primary mover. This means that it generates the majority of the force required to perform a certain movement pattern. For instance, during hip extension, the gluteus maximus functions as the agonist, while the pectoralis major serves as the agonist during pressing movements, and the biceps brachii acts as the agonist during elbow flexion.
Antagonist: When a muscle acts in direct opposition of the agonist, it is called an antagonist. The agonist and antagonist work together through a neuromuscular interaction known as reciprocal inhibition. This means that when the agonist contracts, the antagonist must relax so that the joint can move. For instance, the psoas and the rectus femoris, which are hip flexors, are antagonistic to the gluteus maximus.
Synergist: The muscles that play the role of a synergist are meant to support the primary source of force production, also known as the agonist. Their function is to assist the agonist muscle, but not to become the primary source of force production. For example, when performing pressing movements, the triceps brachii muscle is synergistic to the pectoralis major muscle, whereas the hamstrings assist the gluteus maximus muscle during hip extension.
Stabilizer: The human body has various muscles that work in different ways to support movement. Some muscles work as stabilizers, providing support for the joints, while others work as prime movers or synergists, creating movement. For instance, the muscles of the rotator cuff are responsible for providing support to the glenohumeral joint, while muscles like the deltoids and latissimus dorsi facilitate movement at the shoulder.

Although muscles may vary in their characteristics, shapes, and sizes, they all work together to produce efficient motion. Depending on the movement pattern required, a muscle may act as an agonist, antagonist, or synergist. For instance, muscles that are agonists for flexion become antagonists when the respective joint needs to extend. This understanding enables one to view a muscle’s function in all planes of motion across the entire muscle action spectrum, including eccentric, concentric, and isometric actions.

Skeletal Muscles

Skeletal muscles are often explained in a simplistic manner, stating that they work in one plane of motion and in a concentric manner. However, muscles should be viewed as functioning in all planes of motion and throughout the full muscle action spectrum. To create effective corrective exercise programs, it is important to have a broader understanding of functional anatomy. The following section lists the origins (i.e. beginning attachment point of the muscle), insertions (i.e. where it connects back to the skeleton), isolated (concentric) and integrated (eccentric and isometric) functions, and innervations of the major muscles of the HMS

Leg Muscles

The human leg comprises a complex group of muscles that are crucial for mobility, stability, and strength. Each muscle plays a specific role in our movement patterns, and understanding these muscles is vital for effective corrective exercise and rehabilitation.

Anterior Tibialis: Located in the front part of the lower leg, the anterior tibialis is responsible for dorsiflexion (lifting the foot upwards) and inverting the foot. This muscle plays a key role in activities like walking and running, as it helps clear the foot off the ground.
Posterior Tibialis: Positioned on the inside of the lower leg, the posterior tibialis supports the arch of the foot and aids in foot inversion. It also assists in plantarflexion (pointing the foot downwards). Dysfunction in this muscle can lead to issues like flat feet.
Soleus: Found beneath the gastrocnemius, the soleus is a powerful muscle in the calf. It is primarily involved in plantarflexion, especially during activities requiring endurance like walking and standing.
Gastrocnemius: This calf muscle, visible on the back of the lower leg, works in conjunction with the soleus. It is active during plantar flexion and knee flexion. The gastrocnemius is more involved in explosive movements like jumping.
Fibularis Longus: Also known as peroneus longus, this muscle runs along the outer side of the lower leg. It plays a pivotal role in foot eversion and supports the lateral foot arch. It is crucial for balance and lateral ankle stability.
Biceps Femoris (Long Head): Part of the hamstring group, the long head of the biceps femoris extends the hip and flexes the knee. Located at the back of the thigh, it’s essential for movements like running and jumping.
Semimembranosus: This is another hamstring muscle, lying medially on the thigh. It also helps in hip extension and knee flexion. The semimembranosus plays a significant role in stabilizing the knee joint.
Semitendinosus: Along with the biceps femoris and semimembranosus, this muscle forms the hamstrings. It extends the hip when the trunk is fixed and flexes the knee, while also medially rotating the lower leg when the knee is bent.
Vastus Lateralis: A part of the quadriceps group, the vastus lateralis is on the outside of the thigh. It extends the knee joint and is crucial in activities like squatting and climbing.
Vastus Medialis: This muscle is on the inner part of the thigh. It also extends the knee and plays a vital role in stabilizing the patella and the knee joint during movements.
Vastus Intermedius: Located beneath the rectus femoris, this muscle is a part of the quadriceps group. It extends the leg at the knee joint.
Rectus Femoris: Unique among the quadriceps as it crosses two joints, this muscle extends the knee and flexes the hip. It is essential for activities involving the movement of the thigh and leg.

A comprehensive comprehension of the anatomy and function of leg muscles is important for creating effective corrective exercises and rehabilitation programs. This knowledge is essential not only for athletes but also for anyone who wants to maintain healthy leg function and mobility, as each of these muscles plays a vital role in the complex functionality of the legs.

A detailed breakdown of the Leg Muscles, their origin, insertion, isolated function, integrated function & innervation.

Hip Muscles

The muscles of the hip play a crucial role in human movement, stability, and strength. Understanding these muscles is vital for anyone interested in functional anatomy, particularly in the realm of corrective exercise.

Adductor Longus: This muscle, located in the inner thigh, is responsible for adducting (bringing towards the midline) and flexing the thigh. It plays a crucial role in movements such as crossing legs and stabilizing during walking.
Adductor Magnus (Anterior Fibers): The adductor magnus is a large muscle with anterior fibers that aid in adduction and flexion of the thigh. They also contribute to medial rotation of the thigh, vital for activities like turning and twisting.
Adductor Brevis: Situated beneath the adductor longus, this muscle helps in thigh adduction and stabilization of the hip during movements.
Gracilis: This long, slender muscle extends from the pelvis to the knee. It assists in adducting the thigh, knee flexion, and medial rotation of the leg when the knee is bent.
Pectineus: The pectineus, located at the upper part of the inner thigh, contributes to hip flexion and adduction. It’s active during actions like getting out of a car or climbing stairs.
Gluteus Medius (Anterior Fibers): The anterior fibers of the gluteus medius are crucial for internal rotation and abduction of the hip. They play a vital role in single-leg stability and are often targeted in corrective exercises for hip stability.
Gluteus Medius (Posterior Fibers): These fibers are involved in hip abduction and external rotation, contributing to the stability of the pelvis during activities like walking and running.
Gluteus Minimus: This small muscle, located beneath the gluteus medius, assists in hip abduction and internal rotation. It’s crucial for maintaining hip balance and stability.
Tensor Fascia Latae (TFL): The TFL, located on the outer aspect of the hip, works in conjunction with the gluteus medius and minimus in hip abduction and internal rotation. It also stabilizes the iliotibial band.
Gluteus Maximus: The largest muscle in the body, the gluteus maximus, is paramount for hip extension, external rotation, and maintaining an upright posture. It is heavily engaged in movements like climbing and jumping.
Psoas Major: This deep-seated muscle connects the spine to the femur and is crucial for hip flexion and spinal stability. It plays a significant role in activities such as walking and running.
Iliacus: Working in tandem with the psoas major, the iliacus aids in hip flexion. Together, they are often referred to as the iliopsoas, a major hip flexor.
Sartorius: The longest muscle in the human body, the sartorius, extends from the hip to the knee. It assists in hip flexion, abduction, and external rotation.
Piriformis: This small, deep muscle is located in the buttock area. It is involved in the external rotation of the hip and is a key muscle in many rotational activities.

The hip muscles play a crucial role in numerous everyday activities and movements. Therefore, it is imperative to comprehend their functionality for anyone involved in creating corrective exercise and rehabilitation programs. Having knowledge of these muscles helps in adopting a comprehensive approach to enhance hip stability, mobility, and overall functional movement.

A detailed breakdown of the Hip Muscles, their origin, insertion, isolated function, integrated function & innervation.

Back Muscles

The muscles in the back are crucial for posture, spinal support, and movement and are vital for professionals in functional anatomy and corrective exercise.

Superficial Erector Spinae: This group of muscles, running along the spine, is crucial for extending and rotating the back. They are key players in maintaining an upright posture.
Iliocostalis – Lumborum Division: Located in the lower back, this muscle helps in lateral flexion and extension of the lumbar spine. It supports movements such as bending to the side and standing up straight.
Iliocostalis – Thoracis Division: This mid-back muscle aids in extending and laterally flexing the thoracic spine. It is active during twisting movements and when bending backward.
Iliocostalis – Cervicis Division: Found in the neck, it assists in extending and laterally flexing the cervical spine, playing a role in movements like looking up and turning the head.
Longissimus – Thoracis Division: This muscle extends and laterally flexes the thoracic spine. It is involved in postures that require back extension.
Longissimus – Cervicis Division: Located in the neck, it helps extend and laterally flex the cervical spine, contributing to head and neck movements.
Longissimus – Capitis Division: This division extends and rotates the head, playing a crucial role in actions like turning the head to the side.
Spinalis – Thoracis Division: Primarily involved in extending the thoracic spine, it supports upright posture and back extension movements.
Spinalis – Cervicis Division: It extends the cervical spine, contributing to movements like looking upward and maintaining neck posture.
Spinalis – Capitis Division: This muscle extends the head, aiding in actions like looking up and holding the head upright.
Quadratus Lumborum: A deep muscle in the lower back, it aids in lateral flexion of the spine and helps stabilize the pelvis.
Transversospinalis – Thoracis Division: These deep muscles of the thoracic spine aid in rotation and extension of the thoracic vertebrae.
Transversospinalis – Cervicis Division: Found in the neck, they contribute to the rotation and extension of the cervical spine.
Transversospinalis – Capitis Division: These muscles extend and rotate the head, playing a role in head and neck movements.
Multifidus: A deep back muscle, the multifidus provides spinal stability, particularly during movements of the lumbar spine.
Latissimus Dorsi: One of the largest muscles in the back, the latissimus dorsi aids in movements like pulling and lifting. It helps in shoulder extension, adduction, and internal rotation.

It is crucial to comprehend the back muscles to design effective corrective exercises. Every muscle plays a vital role in supporting the spine and upper body, which is crucial for posture and movement. This knowledge helps in rehabilitation as well as in enhancing overall back strength and function.

A detailed breakdown of the Back Muscles their origin, insertion, isolated function, integrated function & innervation.

Chest and Shoulder Muscles

The chest and shoulder muscles are essential for upper body movement and stability. A thorough understanding of these muscles is crucial for those studying functional anatomy, particularly for designing corrective exercises. This article offers insight into several chest and shoulder muscles, emphasizing their functions and significance.

Serratus Anterior: Located along the side of the ribcage, this muscle plays a pivotal role in protracting the scapula (pulling it forward). It’s essential for activities like pushing and overhead lifting.
Rhomboids: These muscles, located between the spine and scapula, are involved in retracting (pulling back), elevating, and rotating the scapula. They are crucial for postural stability.
Lower Trapezius: This part of the trapezius muscle aids in scapular depression and helps stabilize the scapula during arm movements.
Middle Trapezius: This segment of the trapezius muscle is responsible for retracting and elevating the scapula, playing a key role in upper back strength.
Upper Trapezius: The upper portion of the trapezius assists in elevating the scapula and extending the neck. It’s active in movements like shrugging the shoulders.
Pectoralis Major: A large muscle in the chest, the pectoralis major is responsible for flexion, adduction, and internal rotation of the shoulder. It’s heavily involved in movements like pushing and chest pressing.
Pectoralis Minor: This smaller chest muscle lies beneath the pectoralis major and aids in scapular depression, protraction, and downward rotation. It’s vital for stabilizing the scapula.
Anterior Deltoid: This front portion of the deltoid muscle is involved in shoulder abduction, flexion, and internal rotation. It’s active during movements like lifting the arm forward.
Medial Deltoid: Located at the side of the shoulder, this muscle is key in abducting the arm (lifting it to the side).
Posterior Deltoid: The back part of the deltoid muscle, it assists in shoulder extension, external rotation, and horizontal abduction. This muscle is crucial for movements like pulling and rowing.
Teres Major: This small muscle located near the lower lateral edge of the scapula works in conjunction with the latissimus dorsi in shoulder adduction and internal rotation.
Teres Minor: Part of the rotator cuff, it helps in external rotation and stabilization of the shoulder joint.
Infraspinatus: Another rotator cuff muscle, it is involved in external rotation of the shoulder and stabilizing the shoulder joint.
Subscapularis: Located on the underside of the scapula, this muscle is responsible for internal rotation and stabilization of the shoulder joint.
Supraspinatus: This muscle, located at the top of the scapula, aids in shoulder abduction and is crucial for lifting the arm.

Understanding the functions and interplay of chest and shoulder muscles is crucial for designing corrective exercises that improve muscle balance, shoulder stability, and overall upper body function. These muscles are involved in a wide range of movements and activities, making this knowledge essential for practitioners focused on rehabilitation and functional movement improvement.

A detailed breakdown of the Chest and Shoulder Muscles their origin, insertion, isolated function, integrated function & innervation.

Neck Muscles

The muscles in our neck are essential for supporting the head, enabling movement, and keeping a good posture. To have a better grasp of functional anatomy and corrective exercise, it is vital to have an in-depth understanding of these muscles. This article will discuss various neck muscles, explaining their functions and importance in posture and movement.

Levator Scapulae: The levator scapulae muscle, originating from the cervical spine and attaching to the scapula, plays a crucial role in elevating the scapula. It also assists in neck extension and lateral flexion. This muscle is often involved in neck and shoulder tension, especially in individuals with poor posture or those who sit for extended periods.
Sternocleidomastoid (SCM): This prominent muscle of the neck runs from the sternum and clavicle to the mastoid process of the skull. It is involved in various movements, including flexing the neck, extending the head, and rotating the head to the opposite side. The SCM is not only crucial for head movement but also plays a role in maintaining respiratory function.
Scalenes: Comprising three pairs of muscles (anterior, middle, and posterior), the scalenes are located on each side of the neck. They are primarily responsible for lateral flexion of the neck and assist in neck flexion. Additionally, they play a role in elevating the first and second ribs during forced inhalation.
Longus Colli: A deep muscle of the neck, the longus colli is involved in flexion of the neck and upper spine. It plays a significant role in stabilizing and aligning the cervical spine. This muscle is crucial for maintaining proper neck posture and is often targeted in corrective exercises aimed at correcting forward head posture.
Longus Capitis: Also a deep neck muscle, the longus capitis extends from the vertebrae of the upper cervical spine to the base of the skull. It assists in flexing the head and stabilizing the neck. This muscle is important for head-on-neck movements and is often involved in exercises to alleviate neck strain and improve neck stability.

The muscles in the neck play an important role in daily activities like turning the head, nodding, and maintaining good posture. To design effective corrective exercises, it’s important to understand the anatomy and function of these muscles. By focusing on them, you can address common issues like neck stiffness, poor posture, and imbalances that can cause chronic pain.

Corrective exercises that target these muscles can significantly improve neck function and alleviate discomfort. These exercises are often tailored to improve flexibility, increase strength, and align the cervical spine. Given the risk of neck strain in today’s sedentary lifestyle, it’s crucial to incorporate these muscles into corrective exercise programs to maintain good neck health and function.

A detailed breakdown of the Neck Muscles their origin, insertion, isolated function, integrated function & innervation.

Abdominal Muscles

The abdominal muscles are incredibly important in the world of functional anatomy and corrective exercise. They contribute to core stability and posture, and play a crucial role in various movements and functions. This article will provide an in-depth exploration of the key abdominal muscles, outlining their roles and significance.

Rectus Abdominis: Often referred to as the “six-pack” muscles, the rectus abdominis stretches vertically along the front of the abdomen. This muscle is crucial for flexing the lumbar spine, as seen when performing a crunch or sit-up. It also plays a significant role in stabilizing the pelvis and lower back, and in maintaining internal abdominal pressure.
External Oblique: Positioned on the sides and front of the abdomen, the external oblique muscles are part of the lateral abdominal muscles. They assist in rotating and laterally flexing the trunk, and like the rectus abdominis, they also contribute to abdominal compression. Additionally, these muscles work in conjunction with others to support the spine and maintain posture.
Internal Oblique: Lying underneath the external obliques, the internal oblique muscles operate in an opposite direction. They are integral in trunk rotation and lateral flexion but on the same side of the body. This muscle group also plays a role in respiration, aids in maintaining abdominal pressure, and supports the spine.
Transverse Abdominis: The deepest of the abdominal muscles, the transverse abdominis wraps around the torso, functioning like a corset. It stabilizes the pelvis and lower back before the body moves, making it crucial for preventing injuries, particularly in the lower back. This muscle is often the focus in core strengthening exercises for its role in maintaining abdominal pressure and supporting the spine.
Diaphragm: While primarily known for its role in breathing, the diaphragm is also a key part of the body’s core. As a dome-shaped sheet of muscle that separates the chest from the abdomen, it contracts and flattens during inhalation, increasing the volume of the thoracic cavity. The diaphragm also contributes to increased intra-abdominal pressure, which is vital for stabilizing the spine during heavy lifting or during strenuous activities.

The abdominal muscles are responsible for providing support and stability to the spine while also assisting in trunk movements. These muscles also play a crucial role in breathing and maintaining internal abdominal pressure. In corrective exercise, it is important to understand and target these muscles for improving core strength, posture, preventing injuries, and enhancing overall movement efficiency.

It is essential to incorporate exercises that strengthen these muscles, particularly in a functional and integrated manner, for rehabilitation and fitness programs. A strong and well-functioning abdominal group is fundamental not only for athletic performance but also for daily activities and overall physical health.

A detailed breakdown of the Abdominal Muscles their origin, insertion, isolated function, integrated function & innervation.

Arm Muscles

The muscles in our arms are essential for the different movements we make with our arms and hands. These muscles are divided into various groups, each with unique functions. Knowledge about these muscles is crucial for those interested in functional anatomy and corrective exercise. In this article, we will discuss the primary muscles of the arm, their roles, and significance.ir roles, and significance.

Biceps Brachii: This well-known muscle, located on the front of the upper arm, has two heads (long and short). It is primarily responsible for flexing the elbow and supinating the forearm (turning the palm upwards). The biceps brachii also assists in shoulder flexion.
Triceps Brachii: Positioned on the back of the upper arm, the triceps have three heads (long, medial, and lateral). This muscle is the main extensor of the elbow, playing a crucial role in pushing movements. It also aids in shoulder stability and extension.
Brachialis: Located beneath the biceps brachii, the brachialis is a strong flexor of the elbow. It is particularly active when the forearm is in a pronated (palm down) position.
Anconeus: A small muscle located at the elbow, the anconeus assists in elbow extension. It also helps in stabilizing the elbow joint and may aid in forearm pronation and supination.
Brachioradialis: This forearm muscle, originating near the elbow and inserting on the radius bone of the forearm, is a flexor of the elbow. It is unique in that it assists in flexing the elbow regardless of the position of the forearm (whether pronated, supinated, or neutral).
Pronator Quadratus: A deep muscle in the forearm, the pronator quadratus is a primary pronator of the forearm, turning the palm downwards. It also helps stabilize the distal radioulnar joint.
Pronator Teres: This muscle, also involved in pronating the forearm, runs from the medial elbow to the radius. It assists in elbow flexion and, along with the pronator quadratus, turns the palm downward.
Supinator: As its name suggests, the supinator is primarily responsible for supinating the forearm. It wraps around the upper third of the radius, allowing for rotation of the forearm and hand.

Arm muscles work together for daily activities and sports. Corrective exercise practitioners need to understand these muscles to address issues. Training and rehab targeting these muscles enhance strength and flexibility and reduce injury risk. Balancing exercises improved performance and overall upper body health.

A detailed breakdown of the Arm Muscles their origin, insertion, isolated function, integrated function & innervation.

References

National Academy of Sports Medicine. NASM Essentials of Personal Training. Jones and Bartlett Publishers; 7th edition (Jan. 4, 2021)

National Academy of Sports Medicine. NASM Essentials of Corrective Exercise Training. Jones and Bartlett Publishers; 2nd edition (Jan. 13, 2021)