Download The Kinetic Chain

Chapter 2
Basic Exercise Science
Purpose
• To provide the fitness professional with the fundamental
concepts that pertain to the definition, structure, and
function of the human movement system (kinetic chain).
• By understanding the basic anatomic structures and
physiologic functions, the fitness professional will gain a
comprehensive insight into how the human body operates.
Objectives
• After this presentation, the participant will be able to:
– Explain the basic structure and function of
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The nervous system
The skeletal system
The muscular system
The endocrine system
– Describe how these systems respond and adapt to
exercise
Introduction
• Human Movement System
– Movement is accomplished through the functional
integration of three systems: nervous, skeletal, and
muscular.
– These systems work in concert to produce motion
(kinetic) or human movement.
– All components must work together to produce sound
movement; if one component is not working well it will
affect the others and cause kinetic chain impairments.
Kinetic Chain
• The Kinetic Chain
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Kinetic means force(s).
Chain refers to a system that is linked together or connected.
All components work together to manipulate human motion.
If one component of the kinetic chain is not working properly, it
will affect the others and ultimately affect the movement.
The Nervous System
• The Nervous System
– One of the main organ systems of the body and contains
specialized cells that transmit and coordinate signals,
providing a communication network within the body.
– The nervous system is comprised of two main components
• The central nervous system (CNS) is composed of the brain
and spinal cord
• The peripheral nervous system (PNS) is the nerves that
communicate with the CNS
The Nervous System
• The nervous system is a communication network within
the human body.
• It allows us to gather information about our internal and
external environments, process and interpret the
information, and respond.
• Three primary functions
– Sensory
– Integrative
– Motor
The Nervous System Functions
• Sensory
– The ability of the nervous system to sense changes in either
the internal or external environment.
• Integrative
– The ability of the nervous system to analyze and interpret the
sensory information to allow for proper decision making,
producing the appropriate response.
• Motor
– The neuromuscular response to the sensory information.
The Nervous System: Proprioception
• Proprioception is the body’s ability to sense the relative
position of adjacent parts of the body.
• Training the body’s proprioceptive abilities will
– Improve balance, coordination, and posture
– Enable the body to adapt to its surroundings without
consciously thinking about movement
• Thus, it becomes important to train the nervous system
efficiently to ensure proper movement patterns, which
enhance performance and decreases the risk of injury
The Nervous System
• Movement is a response to sensory information and is
therefore dictated by the nervous system.
– This reflects the importance of training in a multisensory
environment.
• The most effective way to create positive long-term results
in a client is to directly affect (properly train) his or her
nervous system.
The Neuron
• The functional unit of the nervous system is the neuron.
• Neurons are composed of three main parts:
– Cell body
• Includes cell organelles (nucleus, mitochondria, lysosomes,
Golgi complex)
– Axon
• Provides communication from the brain or spinal cord to other
parts of the body
– Dendrites
• Gathers information from other structures of the body
The Neuron
• There are three main functional classifications of neurons
determined by the direction of their nerve impulses:
– Sensory
• Transmit afferent nerve impulses from receptors to the brain or
spinal cord
– Motor
• Transmit efferent nerve impulses from the brain or spinal cord
to the effector sites such as muscles or organs
– Interneurons
• Transmit nerve impulses from one neuron to another
Central Nervous System
• Consists of the brain and the spinal cord
Peripheral Nervous System
• Structure
– 12 cranial nerves, 31 pairs of spinal
nerves (branching out from the brain
and spinal cord, respectively), and all
sensory receptors.
• Function
– Provides a connection for the nervous
system to activate bodily organs, such
as muscles (motor information).
– Relays information from bodily organs
back to the brain, providing a constant
update of the relation between the body
and the environment (sensory
information).
Peripheral Nervous System
• The PNS is subdivided into the somatic and autonomic
nervous systems.
– Somatic nervous system: consists of nerves that serve the
outer areas of the body and skeletal muscle, and is largely
responsible for the voluntary control of movement.
– Autonomic nervous system: supplies neural input to the
involuntary systems of the body
• The autonomic system is further divided into the sympathetic
and parasympathetic nervous systems.
Sensory Receptors
• Specialized structures located throughout the body and
designed to transform environmental stimuli (heat, light,
sound, taste, motion) into sensory information that the
brain or spinal cord can interpret to produce a response.
– Mechanoreceptors respond to mechanical forces (touch and
pressure).
– Nociceptors respond to pain (pain receptors).
– Chemoreceptors respond to chemical interaction (smell and
taste).
– Photoreceptors respond to light (vision).
For relevance to this course, we will focus attention on the
mechanoreceptors.
Mechanoreceptors
• Muscle Spindle
– Sensitive to changes in muscular length and rate of
length change
• Golgi Tendon Organ
– Sensitive to changes in muscular tension and rate of
tension change
• Joint Receptors
– Respond to pressure, acceleration, and deceleration of
the joint
Nervous System and Physical Activity
• Early stage improvements to physical activity are largely
due to changes in the way the CNS and PNS coordinate
movement.
– Unsuccessful activity can be modified with sensory input to
improve performance
The Skeletal System
• Framework for structure and
movement
• Resting ground for the muscles
• Bones form junctions that are
connected by muscles and
connective tissue known as
joints
Divisions of the Skeletal System
• Axial Skeleton
– Skull
– Rib cage
– Vertebral column
• Appendicular Skeleton
– Upper and lower extremities
– Shoulder and pelvic girdles
Bone Growth
• Bones undergo remodeling throughout the life cycle
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Osteoclasts break down old bone tissue
Osteoblasts build up new bone tissue
Remodeling is a constant process in these cells
As children, osteoblasts are more active; as we age,
osteoclasts become more active
Types of Bones
• Long
– Long cylindrical shaft and
irregular or widened ends
– Epiphysis: ends of long bones
– Diaphysis: shaft of long bones;
main production of red blood
cells (RBCs)
– Epiphyseal plate: where bone
growth (length) occurs
Types of Bones
• Long (continued)
– Periosteum: tough membrane
that coats bone
– Medullary cavity: central cavity
of bone where marrow is stored
– Articular cartilage: material that
covers the articular surfaces of
bones
Types of Bones
• Short
– Similar in length and width
– Appear somewhat cubical in
shape
Types of Bones
• Flat
– Thin, protective
Types of Bones
• Irregular
– Unique shape and function
Bone Markings
• Depressions
– Flattened or indented portions
of the bone
– Common depressions
• Fossa
• Sulcus
Bone Markings
• Processes
– Projections protruding from the bone to which muscles,
tendons, and ligaments attach
– Common processes
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Condyle
Epicondyle
Tubercle
Trochanter
Vertebral Column
• Vertebral column: A series of
irregularly shaped bones called
vertebrae that houses the spinal
cord.
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7 cervical (concave curve)
12 thoracic (convex curve)
5 lumbar (concave curve)
Sacrum: a fused triangle
attached to pelvis
– Coccyx: tail bone
Joints
• The structure where one bone articulates with another
• Joint motion is referred to as arthrokinematics
• Typical joint motions seen in the human articular system
– Rolling: one joint surface rolling on another
• Femoral condyles rolling over the tibial condyles during a squat
– Sliding: one joint surface sliding across another
• Tibial condyles moving (sliding) across the femoral condyles
during a knee extension
– Spinning: one joint surface rotating on another
• Head of the radius rotating on the end of the humerus during
pronation and supination of the forearm
Classifications of Joints
• Synovial Joints
– Produce synovial fluid
– Have a joint cavity and fibrous connective tissue
• Knee
• Nonsynovial Joints
– No joint cavity and fibrous connective tissue
– Little or no movement
• Sutures of the skull
Function of Joints
• Provide the bones a means of being manipulated, allowing
for movement throughout segments of the body
• Provide stability, allowing for movement to take place
without unwanted movement
• All joints in the human body are linked together
– Movement of one joint will directly affect the motion of others
Joint Connective Tissue
• Ligaments connect bone to
bone.
• They provide static and dynamic
stability as well as
proprioception.
– Characterized by poor
vascularity
– Do not repair or adapt as easily
as other tissues in the body
Weight Bearing Exercise
• Weight bearing exercise: exercise that forces the body to
work against gravity
– Running, lifting weights, and calisthenics are weight bearing
– Swimming and cycling are not
– Help build and maintain bones, muscles, and connective
tissues, burn lots of calories
The Muscular System
• Muscles generate internal
tension which, under the control
of the nervous system,
manipulates the bones of our
body to produce movement.
Structure of Skeletal Muscle
• Muscle is the compilation of many individual muscle fibers
neatly wrapped together with connective tissue to form
bundles.
– The first bundle is the actual muscle itself, wrapped by an
outer layer of connective tissue called fascia. The inner layer
immediately surrounding the muscle is called epimysium.
– The next bundle of muscle fiber is a fascicle that is wrapped
by connective tissue called perimysium.
– Each fascicle is made up of many individual muscle fibers
that are wrapped by connective tissue called endomysium.
– Each layer of connective tissue extends the length of the
muscle, helping to form the tendon.
Connective Tissue
• Tendons attach muscles to
bone.
• They provide the anchor from
which muscles can exert force
to control the bone and joint.
– Poor vascularity (blood supply)
– Susceptible to slower repair and
adaptation.
Muscle Fibers
• Contain typical cell components
– Cellular plasma (sarcoplasm):
containing glycogen, fats,
minerals, and oxygen-binding
myoglobin
– Nucleus
– Mitochondria: transforms energy
from food into energy for the cell
• Unlike typical cells, they have
structures called myofibrils.
Contractile Elements
• Myofibrils: contain myofilaments that
are the actual contractile components
of muscle tissue.
– Within a myofilament, actin (thin) and
myosin (thick) filaments form sections
known as sarcomeres.
• Sarcomere: the functional unit of the
muscle (like the neuron is for the
nervous system).
– Lies in the space between two Z lines.
– Each Z line denotes another sarcomere
along the myofibril
Contractile Elements
• Two protein structures that are also important to muscle
contraction are tropomyosin and troponin.
– Tropomyosin: located on the actin filament, it blocks myosin
binding sites on the actin filament, keeping myosin from
attaching to actin while the muscle is in a relaxed state.
– Troponin: also located on the actin filament, it plays a role in
muscle contraction by providing binding sites for both
calcium and tropomyosin when a muscle needs to contract.
Generating Force in a Muscle
• Neural Activation
– Essential for a muscle to manipulate force for either
movement or stabilization.
– Generated by the communication between the nervous
system and the muscular system or the motor unit.
• Motor unit = motor neuron and the muscle fibers with which it
connects.
Neural Activation
• Electrical impulses are transported from the central nervous
system down the axon of the neuron.
• When the impulse reaches the end of the axon, neurotransmitters
are released into the synapse between the neuron and muscle
fiber.
• Neurotransmitters cross the synapse, transporting the electrical
impulse from the nerve to the muscle. The neurotransmitter used
in muscle contraction is acetylcholine (ACh).
• ACh attaches to receptor sites on the muscle fiber, which
stimulates the muscle fibers to produce muscle contractions.
• Either a summation causes all motor fibers of a unit to fire or none
(all or nothing law).
Sliding Filament Theory
• The proposed process of how the contraction of the
filaments within the sarcomere takes place
– A sarcomere shortens as a result of the Z lines moving
closer together.
– The Z lines converge as the result of myosin heads attaching
to the actin filament and asynchronously pulling (power
strokes) the actin filament across the myosin.
Excitation–Contraction Coupling
• A nerve impulse (action potential) is transmitted through the neuron to
where the axon meets the muscle fiber (neuromuscular junction) and
releases acetylcholine (ACh) across the synapse.
• The ACh binds to its receptor on the muscle fiber.
• This continues the action potential to the muscle fiber and triggers the
release of calcium (Ca2+) into the sarcoplasm (where the actin and
myosin are located).
• Ca2+ binds to troponin, forcing tropomyosin to move away from the
myosin binding site and allowing myosin to attach to actin.
• Myosin attaches to actin creating a pull of the filaments across each
other, causing the muscle to shorten (contract).
• Once the neural impulse for contraction subsides, calcium concentration
in the sarcoplasm decreases, forcing myosin to unbind with the actin,
ending the muscle contraction.
Muscle Fiber Types
• Type I: Slow Twitch
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Higher in capillaries, mitochondria, and myoglobin
Increased oxygen delivery
Smaller in size
Produce less force
Slow to fatigue
Long-term contractions (stabilization)
• Type II: Fast Twitch
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Lower in capillaries, mitochondria, and myoglobin
Decreased oxygen delivery
Larger in size
Produce more force
Quick to fatigue
Short-term contractions (force and power)
Muscle Fiber Arrangement
Muscle Types and Fiber Arrangements
Type
Fiber Arrangement
Example
Fusiform
Parallel to direction of tendon
Biceps brachii
Fan-shaped
Diverges from broad
attachment to narrow one
Pectoralis major
Longitudinal
Parallel to line of pull
Sartorius
Quadrilateral
Parallel to line of pull
Rhomboid
Unipenniform
Oblique to line of pull
Posterior tibialis
Bipenniform
Oblique to line of pull
Rectus femoris
Multipenniform
Oblique to line of pull
Deltoid
Muscles as Movers
• Agonists: muscles that act as prime movers
– Gluteus maximus is an agonist for hip extension
• Synergists: muscles that assist prime movers during
movement
– Hamstring and the erector spinae are synergistic with the
gluteus maximus during hip extension
• Stabilizers: muscles that support or stabilize the body
while the prime movers and the synergists perform the
movement patterns
– Transversus abdominis, internal oblique, and multifidus
stabilize the low back, pelvis, and hips during hip extension
Endocrine System
• System of glands that secrete hormones to
control bodily functions
– Consists of host organs, chemical messengers,
and target cells
– Target cells bind specifically to hormones
– Regulates body functions (growth, metabolism,
response to stress)
Endocrine Glands
• Primary glands of the endocrine
system include:
– Pituitary: “master gland” with
anterior, posterior, and
intermediate globes
– Hypthalamus
– Thyroid gland
– Adrenal glands
Endocrine Glands
• Pituitary: master control gland has three lobes
– Anterior: secretes growth hormone, prolactin, ACTH (adrenal
glands) TSH (thyroid), FSH (sex organs), and LH (sex
organs).
– Intermediate: secretes MSH (skin)
– Posterior: secretes ADH (fluid retention), oxytocin (childbirth)
Endocrine Glands
• Thyroid gland: regulates metabolism
• Adrenal glands: fight-or-flight hormones and inflammation
(epinephrine “adrenaline” and norepinephrine)
• Testes and adrenal glands: produce testosterone; men
produce 10 times more than women
Blood Glucose Control
• Control of blood glucose levels regulated by the pancreas
to prevent wide swings in blood glucose levels
– Insulin: brings glucose into cells from bloodstream, results in
net drop in blood sugar levels
– Glucagon: signals the liver and muscles to break down
glycogen stores and release glucose into the bloodstream,
results in net rise in blood sugar levels
• Exercise improves the body’s utilization of glucose
The Effects of Exercise
• Epinephrine is released during exercise
– Increases heart rate
– Elevates blood glucose
– Opens airways
• Exercise is response to “flight-or-fight” mechanism
Hormones
• Produced by both men and women
– Testosterone: men produce 10 times more than women, is
produced in testes and adrenal glands, major anabolic agent
– Estrogen: produced in ovaries and adrenal glands, women
produce significantly more than men
– Cortisol: produced in adrenal, main catabolic agent
– Growth hormone: produced in pituitary, major anabolic agent
– Thyroid: located in the neck, controls metabolism
• Exercise can elevate levels of all of these hormones.
Summary
• The three components of the kinetic chain (nervous, muscular,
and skeletal systems) work together to produce movement.
• The nervous system is composed of billions of neurons that
transfer information throughout the body, through two
interdependent systems: the central nervous system and the
peripheral nervous system.
• The skeletal system is the body’s framework and is made up
of bones and joints in two divisions: axial and appendicular.
• The muscular system is made up of many individual fibers
attached to bones with tendons. Muscles generate force
through neural activation, sliding filament theory, and
excitation–contraction coupling.