• Understand the basis for the various principles
of training as well as to evaluate and design
physical fitness programmes.
• Education on how the body adapts to short
and long term exercise, enabling different and
specific programme design.
1) Describe the following systems:
- Cardiovascular system
- Respiratory system
- Neuromuscular system
- Endocrine system
2) Describe the above systems responses to exercise.
3) Describe the acute/short term and chronic/long term
response to exercise.
4) Describe the three energy systems (Phosphogen,
anaerobic and aerobic systems).
5) Identify the energy systems that underpin specific
6) Consider the contribution of energy systems to exercise
Overview of body systems:
• Fig. 3.2 – Different systems work side by side to
fulfil different functions.
• We will focus on the following:
- Cardiovascular system
- Respiratory system
- Neuromuscular system
- Endocrine system
- Energy Systems
• Table 3.1 – Functions of the different body
Overview of body systems (cont.):
• The description and explanation of the body’s response
to exercise and the adaptation to exercise training, to
maximize human performance.
• Eg: why would a 200m athlete not need to do lots of
• In this chapter, the production of energy, and the
application to four broad categories – endurance,
strength conditioning, speed and power and also
• Also, combining what was previously learned, anatomy
– skeletal and muscular systems, with the other body
systems previously mentioned.
• Pg. 81 – words and terms used throughout the chapter.
Components of the heart
• Four chambers
– 2 atria
– 2 ventricles (left
thicker than right)
• Major veins
– Superior vena cava
– Inferior vena cava
– Pulmonary veins
• Major arteries
– Pulmonary trunk
• Valves permit the
passage of blood in
Bicuspid or mitral
• The amount of blood that is pumped by the heart per
• Cardiac output (Q) provides most significant indicator of
circulatory system's functional capacity to meet demands
• Due to the left ventricular muscle being thicker than the
right, the force of ejection is greater as well.
• This is needed as the left ventricle pumps blood to the
entire body, the right only pumps to the nearby lungs.
• Cardiac output (Q) is a product of heart rate (bpm) and
stroke volume (mL – blood pumped by left ventricle every
Q = HR x SV
= 70bpm x 70mL
= 4.9 L/min
•Blood flow from heart increases in direct
proportion to exercise intensity
•From rest to steady-rate exercise, Q increases
rapidly, followed by gradual increase until it
• The percentage of blood ejected out of the
ventricles during each contraction.
• At rest, the ejection fraction is only about
50%. During exercise, it can increase to 100%.
• The ejection fraction at rest is low due to Q
sufficiently supplying all the cell with oxygen.
• As the demand for oxygen increases during
exercise, the ejection fraction increases to
supply the demand of oxygen.
Components of the CVS System:
Blood Vessels: (Vascular system)
• Transports blood throughout the body, to and
from the heart, via systemic circulation.
• Transports blood to and from pulmonary
Different names for vessels:
• Arteries (arterioles) – Carries blood away from
• Capillaries – gas exchange between tissue and
• Veins (Venules) – Carries blood toward the heart.
Effects of impaired blood supply
• The myocardium depends on adequate oxygen
supply as it has limited anaerobic energy-
• Reduced coronary blood flow usually produces
chest pains – angina pectoris.
• A thrombus (blood clot) lodged in coronary
vessels impairs normal heart function –
• MI may be mild, a complete vessel block may
causes myocardium death.
• The heart is able to generate its own electrical
impulses and control the route the impulses take
via a specialized conduction pathway.
The five elements of the pathway:
- SA node – Right atrium, pacemaker
- AV node – Right atrium
- Bundle of His - Septum
- The left and right bundle branches - Septum
- Purkinje fibres - Myocardium
Bundle of His
Left bundle branch
• The pressure of the blood against the walls of the
arteries during the relaxation (diastolic) and
contraction (systolic) of the heart in one cardiac cycle.
• The formula for BP is:
BP = Q x TPR
• Blood pressure is written as systolic (peak value) over
diastolic (minimum value); eg – 120/80 mmHg
• Total peripheral resistance (TPR) is influenced by the
calibre or diameter of the arterioles. Blood pressure
increases more in static exercise (weight lifting) due to
contracting muscle pushing on blood vessels and
• Oxygen extraction occurs at the capillaries, where
they are in contact with skeletal muscle fibres.
• The amount of oxygen extraction is dependent on
the muscle fibre type; slow twitch oxidative fibres
will extract the most oxygen.
• Blood in the veins and venules (venous blood)
has a lower oxygen concentration than blood in
the arteries and arterioles (arterial blood).
• Not all oxygen is removed from the blood, under
• This shows that oxygen supply is not a limiting
factor in exercise.
Oxygen extraction cont.:
• Maximal oxygen uptake (VO2max) is the
maximum amount of oxygen utilised by the
• This is the point maximal consumption is
measured. At rest 3.5 ml/kg/min of oxygen is
needed to sustain life.
• Various VO2max protocols exist and are
conducted under laboratory conditions – Bruce
• The highest VO2 max recorded was 93
The respiratory system:
• The lungs are the organs that perform gaseous
exchange – removal of CO2 and the re-saturation
• The lungs contain millions of alveoli
• As the capillaries are in with skeletal muscle, so to
are alveoli in close contact with capillaries in the
• At this level, gasses diffuse from an area of high
pressure to low pressure, down their
• CO2 from blood to alveoli and O2 from alveoli to
• O2 from the atmosphere travels down the
airways into the lungs, and CO2 in the lungs is
breathed out into the atmosphere.
• At rest 250ml of O2 enters the blood and
200ml of CO2 is expired every minute; during
exercise it increases as much as 25 times.
• Passage of airflow:
Nose/mouth> Trachea> Bronchi>
Bronchioles> alveoli (then reverse)
Mechanism of breathing:
• The diaphragm and intercostal muscles, two
mechanisms control the volume of the chest
cavity to increase and decrease, causing air to
flow in and our of the lungs.
• Inspiration – Increase in the volume of chest
cavity, diaphragm moves down and ribs move up,
the pressure decreases and is lower than
atmospheric pressure, air moves from
atmosphere into the lungs.
• Expiration – Decrease in the volume of the chest
cavity, ribs move down and diaphragm moves up,
higher pressure in lungs than atmosphere, air
moves from lungs into the atmosphere.
• The neuromuscular system is a combination of
the nervous system and muscles working
together to allow movement.
• Strength, speed and power and flexibility
training are all significantly affected by the
• Fig. 3.9 – neuroderms – nerve pairs per body
• Fig 3.8 – a motor neuron
• A neuron is the basic unit of the nervous
system. Two types occur – motor and sensory.
• An axon is the process that extends from a
neuron to connect with another cell.
• Dendrites are little tendrils that receive
conduction towards the cell body.
• Movement can either be voluntary or
• The sensory neuron has a sensory ending, in
skin, muscle etc.
• These endings respond to stimuli and send the
information as an electrical impulse.
• The impulse travels via the sensory neuron to
the central nervous system via the spinal
• The motor neuron receives information from
the central nervous system.
• The information is in the form of an electrical
impulse and it travels down the motor neuron
to the muscle fibre.
• The impulse travels from the motor unit to the
muscle at the neuromuscular junction.
• This results in muscle contraction or
• A motor unit is the motor neuron all and the
muscle fibres it innervates.
• Fast twitch fibres have large motor units and
innervates many muscle fibres.
• They therefore control gross motor control
and produce a great contractile force.
• Slow twitch fibres have small motor units and
innervate few muscle fibres.
• They therefore control fine motor movement
and generate a small contractile force.
• A muscle will respond to stimulus and if the
stimulus is strong enough, the muscle will
• It is not possible for some fibres of a motor
neuron to contract and others not, its all or none.
• Weak muscle contractions are caused by stimuli
of small motor units and strong muscle
contractions are caused by stimulation of big
Structure of skeletal muscle
• More than 660 skeletal muscles in the body
Levels of Organization
• Perimysium covers each bundle (fasiculus) ± 150 fibres
• Epimysium covers the entire muscle and tapers to form the
tendons that connect muscle to the periosteum of bone
• Endomysium covers each fibre
• The origin of muscle refers to the relatively stable end,
proximal or fixed end of the lever or the end nearest the
• The insertion end is the distal attachment to the moving
Muscle fibre type
Type IIa fibres exhibit fast shortening speed and well-developed energy transfer
capacity from aerobic and anaerobic sources, i.e., fast-oxidative-glycolytic (FOG)
Type IIb fibres has the greatest anaerobic potential and fastest shortening velocity,
i.e., fast-glycolytic (FG) fibres
Type IIc fibre is normally rare and undifferentiated , and may contribute to
reinnervation and motor unit transformation.
Slow twitch fibres:
• Low myosin ATPase activity
• Slow calcium handling ability and shortening speed
• Less well-developed glycolitic capacity than fast twitch fibres
• Large and numerous mitochondria
Slow twitch fibres generate energy for ATP resynthesis predominantly
through the aerobic system of energy transfer.
Fibre type differences among athletic
Elite endurance athletes have predominantly ST
fibres in the major muscles activated in their specific
sport, and vice versa for sprint athletes.
Endurance athletes tend toward enlargement of ST
Weightlifters and power athletes show enlargement
in both ST and FT fibres, particularly FT fibres, i.e.,
enlargement of the contractile apparatus, specifically
actin and myosin filaments.
• Fig 3.11 – Myosin (Thick) filaments form cross bridges
with actin (thin) filaments via tiny projections (myosin
• These myosin heads extend from the myosin filament
to the actin filament. The myosin head binding site on
the actin is distant, during relaxation.
• The binding sites are blocked and can only be
unblocked when calcium is released by an incoming
• This unblocks the myosin binding sites and allows the
myosin heads to extend and form cross bridges, pulling
the actin over myosin filaments.
Types of muscular contraction:
• Isotonic – dynamic muscle contraction; either
concentric (shortening – doing a bicep curl) or
eccentric (lengthening – lowering after a bicep
• Isometric – tension in the muscle with no
movement and change in the length of a muscle;
eg. Holding a book in your hand.
• Isokinetic – maximal tension of the muscle while
moving through the movement range. This can
only be obtained on specialized machines -
• A series of glands that produce and secrete hormones
with regulate body growth, metabolism and sexual
development and function.
• Hormones are chemical messengers that transfer
information from one set of sells to another. This has
an effect on functions of that different body part.
• E.g. exercise will cause the adrenal cortex to release
adrenalin. Adrenalin is a hormone that increases heart
rate, breathing rate and prepares the body for the
• The endocrine system is regulated by a feedback
Glands and functions:
• Table 3.6
• The role of hormones is also to maintain
• Homeostasis is the balance of biological
activities in the body, managed by the
• The pituitary gland is the area that triggers the
release or inhibition of hormones.
Hormones and exercise:
• The main hormones that are active during exercise
- adrenalin – readies body for exercise.
- cortisol – protects the body from the stress
- glucagon – triggers release of glucose
from cells and into the blood.
• Others are also active but do not impact as hugely as
the list above.
• The long term effects of training allows for these
hormones to be secreted in lower quantities.
• This is due to the body adapting to exercise and
improves the efficiency of the body.
• Processes required to provide the cells of the body
with the energy required to sustain life and perform
work during activity.
• Many of these processes involve different types of
• A generalized cell consists of a nucleus, cytoplasm and
organelles, all held together by the cell membrane
(cytoskeleton), floating in fluid called cytoplasm.
• Fig 3.13 – different organelles exist in the cells and all
have different functions. For our purposes, take note of
the mitochondria (aerobic metabolism).
Fuels for energy:
• 3 sources of energy (Macronutrients) exist and are
digested when we eat them, namely:
- Lipids (Fats)
• Smaller components of these macronutrients are called
• All of these has a different energy value, kcal.
• 1 kcal = 1000 calories; amount of heat needed to heat
1 kg(1L) of water by 1 degree Celsius.
- Glucose – 4.2 kcal
- Fatty acids – 9.4 kcal
- Amino acid – 4 kcal
• These big molecules requires lots of oxygen to be
mobilized and used as an energy source, more
oxygen than carbs or proteins.
• The intensity of exercise will determine which
energy source is used.
• Fats are stored under the skin (subcutaneously),
around the vital organs and in muscle as
• Fat around organs are essential as they protect
against mechanical shock
• Fat stored subcutaneously is adipose fat and non-
essential and they are mobilised for energy.
• Fat is utilised in its simplest form, free fatty
acids, and usually fuel exercise of moderate
intensity over a prolonged period of exercise.
E.g. – a marathon.
• Fig 3.14 – FFA metabolism and storage
• CHO – stored in the liver and skeletal muscle in
the form of Glycogen (many glucose molecules).
• for CHO to be utilized for energy, it needs to be in
its simplest form of glucose in the blood.
• Stored glycogen therefore needs to be released
from storage before it can be used, this costs 1
• When blood glucose levels are higher than
needed, it gets stored in the form of glycogen.
• Glucose is the preferred source of energy to fuel
high intensity exercise.
• Not a preferred source of energy for exercise.
• Main function is to build, maintain and restore cells.
• Complete proteins sources: eggs, milk, meat, fish, and
poultry (eggs have the highest quality rating - 100)
• Not only do body builders need protein, but endurance
athletes as well.
• Essential vs non-essential proteins.
The Vegetarian Approach
• Soy-protein isolates matches in quality some animal
• Nutritional diversity is the key to successful nutrition
(supplementation is an option)
Intracellular energy systems:
• Understanding these systems, one needs to
understand the fuel sources, chemical structure,
where and how they are stored and the amount
of energy each one produces.
• Fig 3.6 – the metabolic mill – different fuel
sources via different pathways, all to produce ATP
• Three energy systems exist – Phosphogen system,
Glycolysis and Aerobic metabolism – Table 3.7
• O2 independent systems (anaerobic) are
responsible for immediate energy and uses fast
twitch skeletal muscle fibres.
• O2 dependent systems (aerobic) are responsible
for intermediate and prolonged energy
production and predominantly uses slow twitch
skeletal muscle fibres.
• High energy bonds exist between phosphate
groups, when broken down, energy is released
for cellular function (muscle contraction).
• This is illustrated as: ATP ADP + Pi
• ATP stores are limited and can only produce
energy for a few seconds, it has to be continually
The phosphogen system
• Creatine Phosphate (CP) is a high energy compound in
• The bond between creatine and phosphate contains
the energy and when broken, the energy is released for
resynthesis of ATP from ADP and Pi.
• Small amounts of ATP and CP are stored in muscle and
therefore, there is only enough energy stored for about
8 seconds of maximal muscle contraction.
• This energy is instantaneous and important for the
onset of exercise, for a high intensity and short
duration – 100m sprint.
• Once this energy is depleted, the body relies on
glucose for energy (glycolysis).
• Once this energy of the phosphogen system is
depleted, the body relies on glucose for energy.
• Glycolysis generates anaerobic energy from glucose
breakdown to form pyruvate (pyruvic acid) – Fig 3.16.
• This process occurs in the cytoplasm and does not
need oxygen to produce energy.
• Glycolysis only partially breaks down glucose and there
is still energy available in the glucose which can be
• Two ATP molecules are produced via the pathway of
glycolysis along with two lactate molecules.
• When glycogen is broken down, three ATP molecules are
produced, along with two lactate molecules, via glycolysis.
• A by-product of lactate formation is H+ ions. Constant
exercise intensity will cause a build up of H+ ions in the
muscle and blood. This lowers the pH of the blood which
would decrease blood pH and eventually causes muscle
fatigue, as the enzymes do not function optimally at a
lowered pH – Fig 3.18.
• Glycolysis will supply energy for approximately 35 – 60sec,
depending on fitness.
• This pathway will provide a rapid supply of ATP for energy
for an intense, short burst of activity.
• It also acts as an energy reserve for the middle and long
distance athlete to provide a ‘kick’ in the sprint finish, or
provide a footballer with instant acceleration to beat an
opponent. The end product of glycolysis is pyruvate, which
if not used, forms lactic acid, otherwise enters the Krebs
cycle for aerobic metabolism.
Oxygen dependent system (aerobic):
• These processes will occur inside the mitochondria –
the site for ATP production, the powerhouses of cells.
• The greater the amount of mitochondria, the more ATP
can be produced – training effect.
• The Krebs cycle and electron transport chain are 2
pathways through which energy is produced in aerobic
• The end product of glycolysis is pyruvate.
• Pyruvate will build up and form lactate until the
exercise time goes past 60sec, up to 40mins.
• Once past 60sec, pyruvate will enter the Krebs cycle as
Acetyl-CoA, for aerobic metabolism – Fig. 3.16
• The Krebs cycle alone has 10 conversions, yielding 1
• The complete breakdown of glucose will occur via
aerobic metabolism, yielding 36 ATP molecules.
• H2O (used in cell) and CO2 (exhaled) are the by-
products of these reactions.
• When exercise exceeds 40min, lipolysis (the
breakdown of adipose tissue/fat) will
predominately provide ATP.
• One molecule of fat can yield up to 129 ATP, fat
has a high caloric density.
• Unlike anaerobic metabolism (O2 independent),
aerobic metabolism produce large amounts of
ATP without fatiguing by-products (blood lactate
and H+ ions).
• Table 3.7 – Summary.
The Crossover Concept:
• Definition – the exercise intensity at which lipid and
CHO utilization for energy is equal.
High intensity exercise = CHO
Low intensity exercise = Fats
• This concept is the changing in fuel sources due to a
change in muscle fibre types.
• In the trained, crossover = 60 – 70 % VO2max; due
decrease in glycogen stores and an increase in
• These hormones increase lipolysis and therefore
changes the fuel source to fuel exercise.
• Longer the duration, the more reliant on lipids.
• Crossover occurs after 3-5hrs of submaximal work.
Relationship between O2 independent
and O2 dependent systems:
• The intensity and duration will main determinants in
which energy system is used.
- Phosphogen = 8 – 10 sec
- Glycolysis = 30 – 60 sec
- Aerobic metab. = 60sec – hours
• Fig 3.19 – the systems are not mutually exclusive, not
like an on/off switch, but rather a dimmer, working at
100% when needed.
• These systems can be trained and can become more
efficient and the times above will change, depending
• When compared, both systems have advantages and
disadvantages pg. 102 & 103.
• Cardiorespiratory and cardiovascular systems
• Short term response – cardiorespiratory system increases HR by
the release of noradrenaline (sympathetic) – causes increase in the
force of contraction of the heart increased stroke volume
increased ejection fraction.
• since Q=HRxSV, cardiac output increases from 4.2 L/min to 25
• Blood vessels will dilate and reduce TPR, increasing blood flow to
• The body will redirect blood away from the viscera (intestine,
pancreas, etc.) and to the working muscles for oxygen delivery,
supplying the demand.
• Blood pressure will increase due to the cardiac output increasing
• Body core temperature will also increase, resulting in further
vasoconstriction and sphlanchic circulation, increasing blood flow to
the skin for loss of heat via radiation.
• Long term adaptation
1. Heart rate decreases – decrease in sympathetic
2. An increase in capillarisation – more capillaries for
gaseous exchange at the muscle.
3. An increase in muscle mitochondria – more
mitochondria = more ATP produced.
4. An increase in VO2max – increased O2 extraction
5. An increase in plasma volume – increases Q during
• Table 3.9 + 3.10
• The neuromuscular system will account for the
• Short term responses to strength training – pg.
106 – the emphasis being on fast twitch fibres
• Short term responses to flexibility training – pg.
• The stretch reflex – prevents rapid overstretching
of muscle – fig 3.20 – muscle spindles (sensory
organs inside muscle fibres) and Golgi tendon
organs (sensory organs inside tendons).
• Long term adaptations – hypertrophy – increase in muscle
size by addition of myofilaments (actin and myosin).
• Hypertrophy of type II muscle fibres are due to an increase
in protein formation, while type I fibres are due to a
decrease in protein breakdown.
• Hypertrophy of type II > hypertrophy of type I.
• Hyperplasia, splitting of muscle fibres, occur in animals but
are yet to be proven to occur in humans.
• Atrophy, decrease in muscle size, is due to lack of strength
training, decreased neural and mechanical force on muscle
• Main long term adaptations = pg. 107 & table 3.12
• Table 3.11 – long term adaptations of flexibility training.
PHYSICAL AND ENVIRONMENTAL
FACTORS AFFECTING PERFORMANCE.
Homeostasis and feedback loop:
• Homeostasis – maintenance of the internal
environment within a narrow range of temperature, pH
and oxygen consumption.
• Stress, like exercise, induces changes in the body until
that stress is removed/reduced.
• Regular exercise will allow the body to adapt and
function at a higher physiological level – Fig. 3.21.
• Feedback loops, negative (specific to maintain
homeostasis) and positive, help maintain homeostasis
– Fig 3.22.
• If the stressor is applied too intensely, the body cannot
adapt and fatigue/exhaustion will occur.
• The body needs a controlled stressor to avoid this,
which exercise is.
Environment influences (Security,
Work and job clarity
A controlled stressor:
• Exercise is done to improve health and fitness;
fitness defined – pg. 111.
• Exercise is a controlled stressor with specific
responses that occur in muscle, blood vessels
• The purpose of training is to stress the body,
over time, to induce long term adaptation.
• If stress is too little, no adaptation will occur.
• If stress is too much, over-training/fatigue will
occur and lower performance.
General Adaptation Syndrome (GAS):
• The chain of events that occur in response to any
stressful exposure, including the stress of
• Hans Seyle – defined ‘adaptation energy’ – an
intrinsic property which, when at maximum,
coincides with peak performance and when at
minimum, coincides with death – Fig. 3.23
• Three stages of GAS:
– Alarm stage = initial response to stressor.
– Stage of adaptation = improved capacity to deal with
– Stage of exhaustion = body adapts for a long period.
Acute VS Chronic adaptations:
• Acute = temporary nature/short term
– E.g. elevated HR, elevated breathing rate.
– Revert to pre-exercise state when exercise drops.
– Values dependent on fitness of individual.
• Chronic = more permanent/long term
– E.g. mitochondrial adaptations, fibre changes.
– Persist for a sustained period.
– Take longer to wear off.
Exercising in heat:
• Metabolic heat during exercise is eliminated via
the skin surface, dissipated to the cooler outside
environment, via venous blood vessel dilation =
• Sweating dissipates this heat as the evaporation
of sweat causes cooling, preventing the body
temperature to rise 2-3 degrees.
• Excessive external heat with increase in body
temperature may lead to heat stroke.
• Extensive vasodilation may reduce venous return
and reduce stroke volume, increase HR to
increase Q (double demand on circulation).
Exercising in cold:
• Key concern: the body is wet and sweating;
vasodilation is continuing; chilling can occur very
rapidly = wear warm clothing immediately after
exercise, retains body heat.
Exercise performance is affected
- blood will be sent to the central core to
maintain body temperature.
- reduces blood flow to the periphery and
- reduced blood flow will lead to reduced
oxygen delivery and waste removal, reducing
Exercising in humidity:
• Heat combined with humidity can be
- Sweat cannot evaporate readily
- large amount of water vapour in
- difficult for the body to cool and
- exercise > 30min = reduced intensity
Exercising at a high altitude:
• Moderate to high altitude cause a reduction in
the partial pressure of oxygen.
- Less air pressure = less pressure to drive
O2 into blood, in the lungs
- O2 carrying capacity is reduced = reduced
O2 carrying capacity to working muscle
- can result in respiratory distress &
recovery from exercise delayed
- headaches may occur = altitude sickness
- adaptation to altitude is essential
• Training threshold – minimum amount of exercise required
to produce significant improvements in any physical
• Progression – creating an overload to provide continuing
• Individuality – genetic factors, fibre composition, etc.
• Age – some things may be suitable for one age group but
• Gender – some anatomical/physiological differences;
women respond to exercise the same way men do.
• Shape – body composition, structure, influences
• Health & medical status – appropriate programming is
important for what the client presents with.