

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 • • • •
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: – 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 specialised 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
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.
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 multi-sensory 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
• Specialised 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 & 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 • Axial Skeleton – Skull – Rib cage – Vertebral column
• Appendicular Skeleton – Upper and lower extremities – Shoulder and pelvic girdles
Bone Growth • Bones undergo remodelling throughout the life cycle – Osteoclasts break down old bone tissue – Osteoblasts build up new bone tissue – Remodelling 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 (Triquetrum)
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 • • • •
Condyle Epicondyle Tubercle Trochanter
Vertebral Column
• Vertebral column: A series of irregularly shaped bones called vertebrae that houses the spinal cord. – 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
Joint Classifications
• Synovial Joints – Produce synovial fluid – Have a joint cavity and fibrous connective tissue • Knee
• Non synovial Joints – No joint cavity and fibrous connective tissue – Little or no movement • Sutures of the skull
Joint Functions • 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
Connective Tissue
• Ligaments connect bone to bone. • They provide static and dynamic stability as well as proprioception. – Characterised by poor vascularity – Do not repair or adapt as easily as other tissues in the body
Weight Bearing • 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
 
Muscular System • Muscles generate internal tension which, under the control of the nervous system, manipulates the bones of our body to produce movement.
Muscle Structure • Muscle is the compilation of many individual muscle Fibres 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 Fibre is a fascicle that is wrapped by connective tissue called perimysium. – Each fascicle is made up of many individual muscle Fibres 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 Fibres • 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 myo-filaments that are the actual contractile components of muscle tissue. – Within a myo-filament, 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.
Muscle Force • Neural Activation – Essential for a muscle to manipulate force for either movement or stabilisation. – Generated by the communication between the nervous system and the muscular system or the motor unit. • Motor unit = motor neuron and the muscle Fibres 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 fibre. • 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 fibre, which stimulates the muscle fibres to produce muscle contractions. • Either a summation causes all motor fibres 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
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A nerve impulse (action potential) is transmitted through the neuron to where the axon meets the muscle Fibre (neuromuscular junction) and releases acetylcholine (ACh) across the synapse.
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The ACh binds to its receptor on the muscle Fibre.
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This continues the action potential to the muscle Fibre and triggers the release of calcium (Ca2+) into the sarcoplasm (where the actin and myosin are located).
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Ca2+ binds to troponin, forcing tropomyosin to move away from the myosin binding site and allowing myosin to attach to actin.
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Myosin attaches to actin creating a pull of the filaments across each other, causing the muscle to shorten (contract).
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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 Fibre Types
• Type I: Slow Twitch – Higher in capillaries, mitochondria, and myoglobin – Increased oxygen delivery – Smaller in size – Produce less force – Slow to fatigue – Long-term contractions (Stabilisation)
• Type II: Fast Twitch – 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 Fibre Arrangement
Muscle Types and Fibre Arrangements Type
Fusiform Fan-shaped Longitudinal Quadrilateral Unipenniform Bipenniform Multipenniform
Example
Fibre Arrangement
Parallel to direction of tendon Diverges from broad attachment to narrow one Parallel to line of pull Parallel to line of pull Oblique to line of pull Oblique to line of pull Oblique to line of pull
Biceps brachii Pectoralis major Sartorius Rhomboid Posterior tibialis Rectus femoris 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 utilisation of glucose
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 Fibres attached to bones with tendons. Muscles generate force through neural activation, sliding filament theory, and excitation–contraction coupling.