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Kinesiology is the study of human motion which deals mainly with the muscles and their functions. It describes movement, which muscles are involved in the movement, and how exactly they are involved. It explores the muscular involvement in strength exercises and sports technique while biomechanics looks at the physical factors involved in the movement.
Biomechanics is the study of movement, more specifically, the movement (technique) involved in a strength exercise, or in execution of a sports skill. It deals mainly with physical factors such as speed, mass, acceleration, levers, force, and the physical functions of the movement. Some think of biomechanics as the science of movement based on principles derived from physics and anatomy. It explains the “why” and “how” of a movement and strategies to improve it through scientifically-based modifications.
1. Prime Mover, Agonist, or Muscle Most Involved. A muscle is called a prime mover, agonist, or muscle most involved when it is the main muscle involved in a concentric contraction.
2. Assistant Mover. An assistant mover usually plays a secondary role to the prime mover muscles involved.
3. Antagonist. An antagonist muscle is one which has an action directly opposite that of the agonist.
4. Stabilization. When a muscle acts as a stabilizer it steadies or holds a limb and/or body part in place.
5. Synergy. In the field of exercise synergy should be used in two ways. One is helping synergy in which two muscles contract simultaneously to produce one movement for which they are suited, while their other actions cancel each other out. Second is true synergy in which a different muscle contracts to stop the secondary action of another muscle.
1. Concentric Strength. In a concentric contraction the muscles shorten and produce movement. Concentric strength is sometimes known as overcoming strength. In other words, when the muscle contracts, it overcomes the resistance and puts the object or your body into motion.
2. Eccentric Strength. In an eccentric contraction (often known as a yielding contraction), the muscle lengthens (stretches back to its original length) as it contracts. The more the muscle lengthens or the faster it is stretched the greater the tension that is developed. The eccentric contraction plays a very important role in controlling and stopping movement and in preparing the muscles for an explosive type contraction.
3. Isometric Strength. In an isometric contraction you exhibit strength, but there is no movement of the limbs. The muscle develops tension and there is some shortening of the muscle fibers and tendon, but there is no limb or body movement.
When executing a strength exercise, all three muscle contraction regimes are involved. As you perform a movement, the main muscles (agonists) undergo a concentric contraction while the opposing antagonist muscles undergo an eccentric contraction. The adjacent joints and parts of the body that are not in use are stabilized via the isometric contraction. Thus, all three muscle contraction regimes are in operation at the same time, each with a very important purpose.
There are 3 Planes of Movement
Sagittal - Lies vertically and separates the body into left and right parts.
Frontal - Lies vertically and divides the body into anterior and posterior parts.
Transverse (Horizontal) - Lies horizontally and divides the body into superior and inferior parts (top and bottom).
There are 3 Axes of Movement
Sagittal - Passes horizontally from posterior to anterior and is formed by the intersection of sagital and transverse planes.
Frontal - Passes horizontally from left to right and is formed by the intersection of the frontal and transverse planes.
Vertical - Passes vertically from inferior to superior and is formed by the intersection of the sagital and frontal planes.
A muscle can contract with different amounts of force and in different ways to produce different types of movement. This includes:
1. A sustained force movement in which there are continuous muscle contractions to keep moving a weight. In other words, force is applied by the prime muscles involved throughout the ROM.
2. Ballistic movement in which there is inertial movement after an explosive or quick, maximum force contraction. Usually there is pre-tensing of the muscle in the eccentric contraction so that the muscle can contract concentrically with maximum speed and quickness.
3. Guided movement occurs when both the agonist and the antagonist contract to control the movement. Guided movement is seen most often in fine skills such as when you are writing or when you must move the limb through a specific movement pattern.
4. Dynamic balance movements occur when there are constant agonist-antagonist muscle contractions to maintain a certain position or posture.
When you do a strength exercise, the strength exhibited at different points in the range of motion will vary because of the angle at which the muscle pulls. For example, if you do a biceps curl beginning with fully extended arms, it is more difficult to generate sufficient force to start moving the weight than when you start with the arms bent. But the reason for this is that when your arm is straight the biceps muscle inserts at approximately an angle of 10 degrees on the radius bone of the forearm. When the muscle shortens, most of its force pulls the forearm (radius) into the joint to stabilize the elbow rather than to raise the forearm with the weight.
Also known as dorsi flexion, or the movement of the toe area of the foot toward the shin. In this action there is a combination of inversion at the subtalar joint and dorsiflexion at the ankle joint when executing ankle joint flexion. In dorsi flexion(raising the toe area of the foot toward the shin), the tibialis anterior, extensor digitorum longus, and peroneus tertius muscles are the major muscles involved. The toe raise exercise involves dorsi flexion.
Also known as plantar flexion, or the movement of the toe area of the foot away from the body. In plantar flexion there are simultaneous movements of the foot around the subtalar and ankle axes, i.e., a combination of eversion at the subtalar joint and extension at the ankle joint. When you are in contact with the floor, ankle joint extension raises your body, and when you are airborne, it points your toes. In plantar flexion the major muscles of the posterior shin are involved. They are the gastrocnemius, which shapes the back surface of the shin, and the soleus, which is slightly wider than the gastrocnemius and lies directly underneath it. The heel raise and seated heel raise exercises involve plantar flexion.
The two movements of the foot in the subtalar joint are not true ankle joint movements but are usually referred to as ankle movements. They are inversion and eversion, which take place between the talus (ankle bone), the navicular (tarsal bone), and the calcaneus (heel bone). In inversion, also known as adduction or supination, the sole of the foot is turned inward and upward. In eversion the foot is turned outward and downward, that is, the toe area of the foot is pointed outward. These movements are an important part of the pushing-off actions required by athletes in many sports. Development of the muscles involved in eversion and inversion helps prevent ankle sprains. In running, pronation and supination respectively are the terms most commonly used for these actions.
In knee flexion, the shin moves back and up, that is the back of the shin moves toward the back of the thigh, or the back of the thigh moves toward the shin. An example of the latter is the movement of going down in the squat. The hamstring muscle group includes the semitendinosus, semimembranosus, and the biceps femoris. These muscles flex the knee. The Knee Curl exercise involves knee joint flexion.
In extension (the opposite of flexion) the shin moves away from the thigh (or vice versa) and the leg is straightened. When the knee is fully extended, the knee joint is locked in place and no rotation is possible. However, when the knee is flexed, the lower leg can be rotated in or out, but the range of movement is small. Rotation is used most often in the movement of pushing off and turning the body in a different direction. The quadriceps muscle group includes the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius muscles, which extend the knee. The Knee Extension (Leg Extension) exercise involves knee joint extension.
Movement of the thigh forward is called hip flexion. When you are in a standing position, flexion occurs when the leg is raised forward and upward approximately 45° without the pelvic girdle also rotating to increase ROM. When the leg is bent the ROM is increased, and the mass of the abdominal wall then stop hip joint flexion. The major muscles involved in hip joint flexion are the psoas, iliacus, pectineus, and rectus femoris. The Hip Flexion exercise can be done on a hip flexion machine or with active cords.
Extension is the reverse of flexion. In this action the leg is brought down and back to the anatomical straight-line body position from a hip-flexed position. When the leg is in line with the body, it is stopped in its movement by the tension of the ligaments that cross the front of the hips and the psoas and iliacus muscles. The major muscles involved in hip joint extension are the hamstring muscle group and the gluteus maximus. The Hip Extension exercise can be done on a hip extension machine or with active cords.
In hip joint abduction (the opposite of hip joint adduction) the leg is moved from the midline out toward the side of the body. The usual range of motion is approximately 45 degrees. The exact amount depends on the tightness of the opposing muscles, tendons and ligaments. If the leg is raised higher the pelvis will have to go into motion to increase the ROM. The gluteus medius is the major muscle involved in hip joint abduction. The Hip Abduction exercise can be done on a hip abduction machine or with active cords.
Hip Joint medial rotation
In medial hip joint rotation, the femur is rotated inward. This movement can be seen if you keep the leg straight and then rotate it inward, you will see the toe area of the foot rotate inward.
Hip Joint Lateral Rotation
In lateral rotation, the leg is rotated outward. In this movement the femur rotates in a manner opposite medial rotation. If you rotate a straight leg outward, you will see the toe area of the foot rotate out.
Pelvic Girdle Horizontal Abduction
In this action the pelvic girdle rotates on a level plane with the axis either in the spine or in the hip joint. In horizontal abduction the hips rotate outward.
Pelvic Girdle Horizontal Adduction
This movement is the opposite of horizontal abduction, that is, the pelvis rotates on a level plane with the axis in the spine or in the hip joint and the hips rotate inward.
In exercises such as the squat and lunge there is a combination of knee joint extension and hip joint extension. The muscles involved therefore are the muscles involved in knee extension and hip extension.
Flexion, or forward bending of the spine, is movement where the anterior surfaces of the vertebrae move closer to one another. Spinal flexion involves the abdominal muscles, which include the rectus abdominis and the internal and external obliques. The sit-up exercise involves spinal flexion.
Extension is the return from a position of flexion to the anatomical position. It is the opposite of flexion. Going beyond the anatomical position (bending backward) is called hyperextension. Two sets of muscles are involved in extension of the spine: a deep spinal group and a superficial spinal group. The back raise exercise involves extension of the spine.
Lateral flexion, is bending sideways to the right or left. In this action the shoulders move toward the hip, or the hips (pelvis) move toward the shoulders when the hips are in a non-support hanging position. In side bends the quadratus lumborum, the internal and external obliques, the rectus abdominis, and the erector spinae muscles are involved in lateral flexion of the spine.
Shoulder (shoulder girdle) rotation, is a twisting action around the long axis of the spinal column. In this movement the shoulders (or hips) are in motion. Shoulder rotation can also occur with the axis in the left or right side of the body. Twisting exercises such as the standing twist or Russian twist involve shoulder (shoulder girdle) rotation.
If you are positioned so that your body is hanging, supported by your arms, the abdominal or lower back muscles rotate your hips to the right or left while your shoulders remain stationary. This is also known as transverse pelvic girdle rotation. In the reverse trunk twist exercise, the internal and external oblique muscles are involved in rotation of the pelvic girdle.
Shoulder joint flexion is movement of the arm upward and in front of the body. The anterior deltoid, the pectoralis major (upper portion), and the coracobrachialis are the major muscles involved in shoulder joint flexion. The front arm raise exercise involves shoulder joint flexion.
Shoulder joint extension is movement of the arm down and to the rear. The major muscles involved are the sternal or lower portion of the pectoralis major, the latissimus dorsi, teres major, posterior deltoid, and long head of the triceps. The seated row exercise with a neutral grip involves shoulder joint extension.
Shoulder joint adduction is movement of the arm sideward and downward towards the body. The major muscles involved in shoulder joint adduction are the latissimus dorsi, the teres major, and the lower pectoralis major. The pronated wide grip variant of the lat pulldown exercise involves in shoulder joint adduction.
Shoulder joint abduction is movement of the arm sideward and upward away from the body. The major muscles involved in shoulder joint abduction are the deltoid and the supraspinatus. The lateral dumbbell arm raise involves shoulder joint abduction.
Shoulder joint horizontal adduction is movement of the arm horizontally towards the front of the body. In this action, also known as horizontal flexion, the major muscles are the pectoralis major, the coracobrachialis, and the anterior deltoid. The dumbbell fly (butterfly) exercise involves shoulder joint horizontal adduction.
Shoulder joint horizontal abduction is movement of the arm horizontally from the front of the body towards the side. In this action, also known as horizontal extension, the major muscles involved are the middle and posterior deltoid, the infraspinatus, and the teres minor. The lateral prone raise (reverse fly) exercise involves shoulder joint horizontal abduction.
Shoulder joint lateral rotation is rotation of the humerus outward. In this action the major muscles involved are the infraspinatus and the teres minor.
Shoulder joint medial rotation is rotation of the humerus inward. In this action, the major muscles involved are the subscapularis, the latissimus dorsi, and the teres major.
It is possible to elevate and depress the shoulder girdle. In this case the entire shoulder girdle (clavicle and scapula) is raised upward in an action called shoulder girdle elevation; lowering the shoulder girdle is called shoulder girdle depression. In the shoulder shrug exercise there is elevation of the clavicle and scapula, which involves the upper trapezius, levator scapulae, and rhomboids. In this action the shoulder girdle is raised directly upward (vertically).
In elbow joint flexion the forearm moves toward the upper arm or vice versa. The major flexor muscles of the elbow joint are the biceps brachii, brachialis, and brachioradialis muscles. The biceps curl exercise involves elbow joint flexion.
In elbow joint extension the forearm moves away from the upper arm in an arm-straightening action. The reverse action, in which the upper arm moves away from the forearm, is also possible. This is seen in the lowering phase of a pull-up or chin-up. Only one major muscle is involved in elbow joint extension - the triceps brachii, which is a large muscle that covers the entire back side of the upper arm. The triceps pushdown exercise involves elbow joint extension.
Only two actions are possible in the radio-ulnar joint: supination and pronation. In supination the forearm is rotated so that the hand is turned palm up. In supination, the supinator muscle acts alone in slow or fast movements. The biceps brachii comes into play when supination occurs against resistance or when supination is done quickly with the elbow flexed. The exercise that most effectively develops the supinator and pronator muscles is supination and pronation with the Strength Bar.
Only two actions are possible in the radio-ulnar joint: supination and pronation. In pronation the forearm is rotated so that the hand is turned palm down. The pronator teres and the pronator quadratus muscles are involved in pronation. The exercise that most effectively develops the supinator and pronator muscles is supination and pronation with the Strength Bar.
The wrist joint can undergo flexion, in which the palm side of the hand moves toward the forearm. The flexor carpi ulnaris and the flexor carpi radialis muscles are involved in wrist joint flexion. In this action the palm side of the hand moves toward the forearm. The wrist curl exercise involves wrist joint flexion.
The opposite movement of wrist joint flexion is wrist joint extension-hyperextension, in which the back of the hand moves toward the posterior surface of the forearm. The extensor carpi radialis longus and brevis and the extensor carpi ulnaris are involved in wrist joint extension-hyperextension. In this action the back of your hand moves toward your forearm from a wrist flexed position. The reverse wrist curl exercise involves wrist joint extension.
Wrist adduction (also known as ulna flexion) is movement in which the little finger side of the hand moves toward the body when the arm is in the anatomical position, that is, when the palm faces forward and the hand is alongside the body. Another way to describe this action is to see the little finger side of the hand moving toward the forearm while the hand is kept in line with the forearm. In ulna flexion (hand adduction) the flexor carpi ulnaris and the extensor carpi ulnaris muscles are involved. In this action the little finger side of the hand moves toward the forearm.
The opposite of wrist adduction is abduction, also known as radial flexion, in which the thumb side of the hand moves away from the body when the arm is in the anatomical position. In this the thumb side of the hand moves toward the forearm while the hand remains in line with the forearm. In radial flexion (hand abduction), the flexor carpi radialis and the extensor carpi radialis longus and brevis are involved. In this action the thumb side of the hand moves toward the forearm.
A combination of all the wrist movements produces circumduction. In this movement, the hand turns around so that the fingers circumscribe a circle and the hand a cone. In many respects the wrist joint is analogous to the ankle joint because it consists of more than one joint with different actions taking place in each joint.
There are compound exercises that involve movements in both the should and elbow joint. The bench press exercise involves shoulder joint horizontal flexion (adduction) and elbow extension. The overhead press (military press) exercise involves shoulder joint flexion and elbow extension. The chin-up (supinated or neutral grip) exercise involves shoulder joint extension and elbow joint flexion.
The quadriceps femoris group, located on the anterior (front) side of the thigh includes the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius muscles, which extend the knee.
The hamstring muscle group includes the semitendinosus, semimembranosus, and the biceps femoris. These muscles flex the knee.
The gluteal muscle group that makes up the buttocks includes the gluteus maximus, gluteus medius and gluteus minimus.
The abdominal muscles include the rectus abdominis and the internal and external obliques. They are involved in spinal flexion and twisting.
The major flexor muscles of the elbow joint are the biceps brachii, brachialis, and brachioradialis muscles.
The triceps brachii is the arm extensor muscle. It is a large muscle that covers the entire back side of the upper arm. It is divided into three sections, known as the lateral (outer) head, medial (middle) head, and long (inner) head.
The wrist flexors (Flexor carpi radialis, Palmaris longus and Flexor carpi ulnaris) are located on the front of the forearm, i.e., on the palm side of the hand.
The wrist extensors (Extensor carpi radialis longus, Extensor carpi radialis brevis and Extensor carpi ulnaris) are located on the back of the forearm, i.e., on the back of the hand side of the forearm.
The adductor muscles of the thigh (adductor longus, brevis, and magnus, and the gracilis) are involved in hip joint adduction.