Exercise

ANATOMY AND PHYSIOLOGY

Anatomical Analysis
The chief methods of anatomical analysis have been body dissection; dissection slides; clinical slides; MRI; film: Surface & biomechanics; illustration and nowadays motion capture. As a result, today the gold standard in anatomical education is incredible Anatomy.tv.
In terms of modern medicine at a macro level most is now know, at a micro (cellular) level we have already mapped the entire human genome, and now we face the task of unavelling the communication occuring between the many systems of the human body.
Body Types
Western medicine has classified human structure into 3 broad " somatotypes ". They were linked to the dominance of certain tissue types during fetal development:

Ectomorphic » Characterized by long thin bones, angular features, with deep rib cages (allowing for larger lung capacity) and a nervous personality type. Stereotypically they have the build of long distance runners.
Mesomorphic » Medium-sized bones, they tend to develop lean muscle bulk quite readily, as is best evidenced in 100m sprinters. Strong physiques, associated with dominant personality types.
Endomorphic » Thick, short bones, their large powerful joints and rounded physiques make them ideal long distance swimmers and power lifters. Endomorphs were said to fit the jovial laid back stereotype, where thoughts of the next meal are foremost in mind.

In reality however, our bodies and personality types consist of a blend with one component possibly dominating. Consult web sites such as the English Institute of Sports (EIS) for athlete body typing, in order to see what sport you are best suited to excel at.
Hormonal Systems
Human endocrine structures (Image "drstandley.com")
Human structure is composed of self created proteins. The proteins are built based on genes which are labelled "turned on" for expression within the DNA of the specific cells. This process of manufacturing proteins is known as transcription. Our growth, maintenance and repair are regulated by hormones. The hormones are produced by glands scattered around the body. Their regulation is controlled by what is termed the Endocrine System. This system assesses the stress we place on our bodies during exercise and and repsonds accordingly.
Humans have a Central Nervous system (CNS) linked to a Peripheral Nervous system (PNS) which together are responsible for actions taken under our conscious control. We also have an Autonomic Nervous System (ANS) under unconscious control ... which is why we don't have to remember to breathe! The ANS is controls glands positioned around the body, by releasing chemical messengers known as hormones.
This ANS has two parts to it. The Sympathetic Nervous System (SNS), dubbed the Fright, Flight, Fight and Fornication system, is responsible for our survival as a species. The Parasympathetic Nervous System (PSNS) is responsible for our ingestion and assimilation of nutrition amongst other things. It is what builds up the bodies stores of vital energy. The trick is that the SNS and PSNS are required to balance one another out. Excesses in either direction are detrimental to the body.
Stress, whether in the form of exercise or mental anxiety, activates the SNS i.e. the body reacts the same to physical danger as it does to anxiety building up in the mind. This is because the human brain and nervous system is not as logical in processing input as we used to think. It is hit with masses of different data from all over the body, and uses a form fuzzy logic to process and respond, sometimes in a split second. For more on this (click). So with our modern lifestyles often involving been stuck behind a desk, and under constant mental pressure, the body automatically turns up the SNS to help us out. This is not fatal on its own, but the SNS was design to be used as an emergency boost only. The remainder of the time the PSNS was meant to be turned on and building- up our energy levels.

Here's how the body synthesizes hormones. It along the adrenal gland hormonal pathways chart (right), gives an idea of why we need to eat animal products to get the cholesterol which is used by our bodies to create hormones. It also indicates that when a body is stressed, the sympathetic nervous system goes into mass production of cortisol (a powerful stimulatory hormone). But in order to produce the cortisol, the body must "rob" other PSNS related hormonal of their hormonal precursors (hormonal building blocks). Since these precursors are the same building blocks hormones related to repair and growth for example are reduced dramatically in order to cater for this stimulatory affect.
Human Growth Hormone
The Auto-immune System
During fetal development we obtain our cellular nutrition and exchange gases with our mothers by means of osmosis within the placenta (a sac within the womb connecting the mother to the umbilical cord). At this stage the foetus had no immunity to speak of. Our initial source of immunity is that which is delivered to us via the breast milk of the mother. This temporary situation buys us enough time to begin developing our own immune system. Genetically our parent would have passed over immunity related information via their DNA. This information tells us what proteins our body Does Not manufacture. This information is taught to constituents of our white blood cells. Those cells will then automatically sense sense for foreign proteins (antigens), and if detected unleash various mechanism which hunt and destroy the foreign cells responsible for producing the antigens.
The body has 2 basic systems of dealing with infection and disease:
The Cell Mediated Immune Response [Basic Level]
The Antibody Mediated Immune Response [Basic Level]
If our ANS is "out of sync", that is if we are under too great a stress and the SNS is having to dominate over the PSNS to stimulate us, then our immune system becomes compromised and we become prone to illness. One of the reasons sleep is so important is that it gives the SNS some "down-time", thus our PSNS can boost our immune system. similarly over training creates prolonged stress thus our SNS become over worked and again our immunity is compromised.
The Lymph System

Inflammation
Inflammation is the bodies natural response to damage, this is irrespective of whther it is caused by mechanical trauma, bateria, pathogens or viruses. For more information on this see (Soft tissue).
Further Sources For Physiology
YouTube - Anatomy, Neural Science & Physiology - Animations [Basic Level]
McGaw-Hill Higher Education - Get Body Smart [Intermediate Level]
John Kyrk - Cellular Biology [Intermediate Level]
The Central Nervous System (CNS) and Musculoskeletal Movement
Nervous System Overview
Cranial nerves connec the brain directly your sense organs (eyes, ears, nose, mouth).
[However the majority of sensory information actually comes from receptors embedded within fascial connective tissue covering the body].
Central nerves connects the brain and spinal cord.
Peripheral nerves connect the spinal cord with your limbs.
Autonomic nerves connect the brain and spinal cord with your organs (heart, stomach, intestines, blood vessels, etc.). These nerves make up the Autonomic Nervous System (ANS), which functions automatically. It is broken down itnot to competing systems which in a healthy individual balance each other out. The Parasympathetic Nervous System (PSNS) is repsonsible for building up the bodies energy stores, whilst the Sympathetic Nervous System (SNS) stimulates the body to higher levels of performance when the body is under stress.
The Brain
The brain forms part of the CNS. The brain is composed of specialized groupings of neurons, and three times as many supporting glial cells, floating in shock absorbing cerebrospinal fluid. Neurons have mutliple dendrite extensions and a single axon, which allow for communication. Neurotransmitters however allow for the actually tranfer of impulses between neurons and also to muscle fibres. Glial cells regulate impulse propogation and neurotransmitter uptake.

The human brain (Blogopithecus).

Cerebrum > The movement thought happens at the front of the brain.

Supplementary Motor cortex > responsible for planning and coordination of complex movements from memory.

Pre Motor Cortex > responsible for movement guided by sight, sound, etc.

Basal Ganglia > filter ... the thought fires nerves controlling many different movements, the filter determines which movements in the past allowed us to achieve a similar goal movement.

Motor cortex > receives muscle stimulatory & inhibitory messages from the Basal Ganglia and passes it on to the cerebellum to check whether it can be implemented at that moment.
Cerebellum > It must perform a real-time check to see if it is practical considering the current circumstances (our environment, our body position etc. to implement the movement plan.
Cerebellum takes proprioceptive feedback (the bodies internal GPS) from receptors in our fascial linings beneath our skin and surrounding all our organs, bones, muscles and connective tissues) AND compare it to the Movement Plan.
Furthermore, fluid in the ear canal also acts as a "spirit level" for the head. Three semi-circular cannals, found in the inner ear, form a biological gyroscope. Prorioceptive feedback is also comapared to information obtain via the vestibular nerve, attached to sensory cells surrounding the hairs which monitor fluid levels within the ear canal. This adds to the full positioning picture.
Positional feedback from the Vestibular System of the inner ear (Medicinenet.com).
The Cerebellum then either sends the Movement Plan back to Motor Cortex to adapt the movement OR send it to the muscles to perform.
Nerve Tissue

Images: Neurons and Cross section of a nerve (How Stuff Works).

The impulses for movement leave the brain via Descending Motor Tracts (in the brain stem). They travel down the spinal cord (conus) then exit spinal cord at various levels of the vertebra (bones of the spine): 7 cervical vertebra (neck); 12 throracic vertebra (torso); 5 lumbar vertebra; 5 fused sacral vertebra and 4 cocycx vertebra. Below the 1st lumbar vertebra (L1) the thick spinal cord (conus) branchesin to the "cauda equina" - fine branches of nerves which resemble a horses tail. The nerves exit the vertebra then collect and regroup around certain areas e.g. the shoulder (Brachial Plexus). From the these collection points they run down the body branching off into nerves which lead to collections of muscle fibres known as motor units. These nerves connects to the muscles through what is called the Neuromuscular Junction (NMJ).
For more on nerves - How Stuff Works.
Connective Tissue
Overlooked for centuries, connective tissue, or fascia, is today seen as one of the most important and interesting components of the human body. Recent findings amongst other things highlight it's importance with regard to bio-tensegrity, proprioception and perhaps piezzo electric circuitry.

Bio-tensegrity is the fancy word used to describe how our body shape is formed by the fascial sling which envelopes every part of our bodies, including the muscle and bones. Superficial fascia lying beneath the skin (dermis) forms the dense yet flexible layer which gives our bodies their smooth organic lines and more importantly houses fatty deposits used by the body as a natural battery of energy.

Deep fascia forms a steel like mesh of support, when the muscles contract they alter the tension in the connective tissue allowing the bones to move. In addition this connective tissue stores up kinetic energy generated during movement. This is seen in sprinters where initial movements are our by fast-twitch muscles running of our phosphocreatine energy system. As our bodies gain momentum during movement the connective tissue is stretched like an elastic band and we are the able to use the stored up energy saving our demand for energy and increasing our power. Our ability to use this recoil off the connective tissue is enhanced through training plyometric movement patterns.

Muscles are housed in compartments which slide over one another. A lack of movement, poor nutrition/hydration, trauma or disease and affect the fascia's structural integrity. Trauma and lack of (or simply poor) movement causes adhesions to form. Adhesions occurs when "extra cellular matrix " leaks out of the fascial sheaths, bonding the sheath to neighboring structures. Movement, stretching and specific manual therapy can break this glue.
Books and Ideas Podcast #15: Dr. Robert Schleip discusses Fascia.
View an illustration of fascia and adhesioning ("Ida Rolf - Philosophy ").
Witness a dissection of fascial adhesions in a body ("Fascia - Gill Hedley's ").
Muscle
Muscle, we could always do with a little more! Muscle tissue is instructed via our nervous system. Muscle under voluntary control, responds to the conscious thoughts transmitted by the central nervous system. We also thankfully, have muscle tissue under involuntary control, such as the heart muscle.
There are 3 classes of muscle:

Cardiac Muscle (myocardium) - Only found in the heart, we have no voluntary control over it. It is stimulated by tiny electrical pulses and must burn fuel in the presence of oxygen, so as to power its contractions.
Cardiac cells die in the absence of oxygen (cardiac infarction) - smaller attacks which may lead to heart attacks. A heart attack refers to a disturbance (cardiac arrhythmia), which unless corrected may result in cessation of the contractions.
Smooth Muscle - Found in all the tubes within the body and is also involuntary muscle e.g. the intestines, trachea and blood vessels.
Skeletal Muscle (striated) - It's the tissue, which along with fat, gives our body its shape and is responsible for moving our bones. We have conscious control over it, although our postural muscles are thankfully under involuntarily controlled.

As man has evolved and adapted to various environments, geographical origin has resulted in distinctive characteristics. Epigenetically a cellular memory of a required physical trait, once developed, can the be inherited by future offspring. In the case of athletes, this can allow for a competitive advantage. Obvious examples of this being the high-density slow twitch muscle fibres found in East African middle distance runners and the high density fast-twitch muscle fibres found in West African/Caribbean sprinters. In moving we automatically access a number of muscle fibre types and energy systems in varying combinations.
Skeletal muscle tissue consists of a mix of three main types of muscle fibres:

Type 1/ Slow-twitch / Slow Oxidative fibres » are the red fibres. Rich in haemoglobin, accounting for the red appearance. Slow twitch fibres burn up large quantities of glucose, fatty acids, in emergencies even cannibalising muscle protein (a process known as gluconeogenesis). They are slow in responding to stimulus by the nervous system, but their efficient use of energy makes them the ideal " work horses," powering long distances athletes reliably for extended periods of time.
Type 2A / Intermediate / Fast Oxidative-Glycotic fibre » pink in colour and is precisely that- a fibre possessing the characteristics of both fast and slow twitching muscle fibres. It's an important fibre to be aware of, since through specific training, it can take on the characteristics of either red or white fibres.
Type 2B / Fast-twitch / Phasic / Fast Glycotic fibres » are bulky and white in colour and heavy. They produce incredibly quick response times, a density of these fibres being the hallmark of 100m sprinters. Powered by the creatine phosphate system, as opposed to the glucose/fat burning aerobic & anaerobic systems, there is an absence of the red oxygen carrying haemoglobin found in the blood capillaries. They " burn " and loose their fine neural control (ionic pump " melt down ") when challenged. They also tend to shorten when over worked.

Let's consider what is going on within the muscles fibres at microscopic level.
(View an illustrated dissection of a muscle).
The muscle fibres are basically composed of lengths of myofilaments (composed of acthin and myosin). Once instructed, the body uses the energy released, as the phosphate molecule break off an ATP (adenosine tri-phosphate) molecule to form ADP (adenosine di-phosphate). This energy is then used by the myosin heads, to crawl along the acthin filaments, thereby shortening or lengthening the muscle.
Muscles are attached by tendons to bone, their shortening or lengthening is what moves our limbs. This movement is guided by ligaments (which attach bones to one another).
Due to the mechanics involved in lifting a weight, it starts out being difficult, getting progressively easier as more and more motor units (collections of muscle fibres controlled by a single neuron) become involved. As we run out of extra units to recruit, toward the end of the lift, it becomes a struggle again.
It is also interesting to learn that we are in fact strongest during the eccentric phase of muscle contraction (the lowering of a weight), as opposed to the concentric phase (the lifting of a weight). For this reason bodybuilders will for example lower weights more slowly and perhaps even use heavier weights during the eccentric phase of a lift.
Fat
Body weight is effectively composed of bone, muscle, fat and fluid. Most fat cells are found embedded in the superficial layer of fascia just below the skin. They serve as a fantastically efficient bio-battery for the human body.
It is thought that we are born with a genetically predetermined number of fat cells (adipocytes). The fatty acids contained by these cells are not only burnt off as fuels, but are in fact vital ingredients for a host of other bodily functions.
Being such an efficient battery, it is a proactive one, possessing a form of bio-intelligence. Our bodies " learn " from previous shortages in fuel supplies, by stock piling extra fat should it become available. This has implications for those involved in the haphazard " yo-yo dieting". Repetitive deprivation of fuel, causes the body to process and store the food which it may normally simply have expelled for lack of need. It may take a considerable period of time before the body re-corrects this. In addition, dieting conditions us to ignore the hunger related signaling, naturally generated by the body, in order to regulate a healthy eating pattern.
Carbohydrates (glucose), proteins (amino acid) as well as dietary fat may be converted into appropriate fatty acids for storage. Excessive intake of nutrition (i.e. eating volumes greater than required), will thus lead to an expansion in the size of our fatty tissue cells.
Fat distribution in the body is governed by the hormonal regime. As a result of their hormonal make up, healthy woman naturally have a higher body fat percentage (around 25%) than men (around 18%). These figures may vary slightly according to ethnicity, as we have had to adapt to various climates, food sources and lifestyles over thousands of years. Abnormally low body fat percentage results in amongst other things: a layer of downy hair growth on the skin to heat up the body; low immunity; a loss of menstrual cycle in females. Men thus tend to store excess fat around the front of the abdomen, whereas in woman it is typically found at the front of the abdomen, as well as in the buttock, thigh, and breast areas.
Bone
An adult skeleton is made up of 206 bones, the majority of which are to be found in the hands and feet. Although the skeleton provides the structure which enables body movement, its main role is in fact to store minerals, in particular calcium which is used by the nervous system.
There are 4 types of bone: long bone (limbs e.g. femur), short bone (strong and compact e.g. tarsus), flat bone (protection e.g. ribs) and irregular bone (e.g. vertebrate).
In terms of exercise, we need to be aware of the basics- running from head to toe: the skull, spine (cervical vertebrae, thoracic vertebrate, lumbar vertebrae, sacrum, coccyx), ribs & sternum, shoulder girdle, shoulder joint, upper arm (humerus), lower arm (ulna and radius), hand (carpals, metacarpals, phalanges) pelvic girdle, pelvic joint, upper leg (femur), knee joint, lower leg (fibula and tibia), foot bone (calcaneum), toes (tarsals, metatarsals).

Contraction and relaxation of skeletal muscle groups is what moves our limbs. Fully developed after 18 years in woman, 25 years in men, their density is constantly being regulated to meet the demands placed upon them.

The bones found in our skeletal system create the structure for our bodies, housing our internal organs, at the same time being used as levers for movement by our muscles. Surprisingly however, their main role is in fact one of storage, housing our vital mineral supplies, especially calcium, which is a vital ingredient in the functioning of the nervous system.
We are able to prepare our bones to take knocks through weight-bearing exercise, which causes an increase in bone density over time. This is phenomenon is known as Wolf's Law.