Intro Outline 11/05/2014

What are the sub-disciplines of exercise science?

 Chapter 1- Intro to Exercise Science

∙ new fields of study are often formed by mergers of several  

disciplines

∙ exercise science is formed from fields like biology, physics,  

mathematics, chemistry, psychology, and medicine

Subdisciplines (areas of focused study) of Exercise Science

∙ exercise physiology and biochemistry-how physiologic systems  respond to human movement

∙ biomechanics-physical principals that underlie human motion  ∙ motor learning and control

∙ exercise and sport psychology-scientific study of psychologic  issues in human behavior related to movement

What is exercise biochemistry?

∙ sports medicine

 Scientific evidence We also discuss several other topics like Hydrophobic interaction means what?

∙ objectivity-research methods used must be objective, and  observations made must be trustworthy, reliable, and based on fact ∙ scientific evidence-available through controlled and objective  scientific studies published in scientific journals; subject to peer  review before publication If you want to learn more check out Contribution margin ratio means what?

∙ anecdotal evidence-obtained from information that may not  represent clear data or clear fact

o available through media and sources not subject to scientific  scrutiny

 often are “one-shot” observations

 ex: a young man collapsed and died while exercising  

causes people to believe that exercise is bad

What is an example of anecdotal evidence?

Anecdotal Evidence (methods)

∙ testimonial approach-a manufacturer finds several people who  have tried a product and will say that it works great Don't forget about the age old question of In 2013 what is the life expectancy of japan?

o useful for evaluating whether a product is worth considering o form of anecdotal evidence

∙ tenacity-a story is told so many times that it is believed to be true o ex: superstitions

∙ knowledge of authority-when the source of info is an expert o consumers need to evaluate all sources of evidence to make  an informed decision

∙ rationalistic method- ex: Jane is a good bball player. Jane eats  wildflowers. Therefore, wildflowers must promote good basketball  playing ability. If you want to learn more check out What is the definition of government?

 Scientific Method

∙ observation-scientist observes a phenomenon and wants to explain  it

∙ hypothesis-logical explanation for the phenomenon

∙ experiment-scientific study designed to ask a very specific question ∙ (revision of experiment) Don't forget about the age old question of Holism refers to what?

∙ theory

 Research

∙ Statistical analysis-helps us differentiate between the results  observed in one individual and the results we can expect from  observing a large group of individuals

∙ basic research- facts; lays foundation for applied research o ex: Laws of Motion

∙ applied research-research that has obvious applications to solve a problem or answer a research question

o ex: learning how to build faster bicycles, design better training schedules

∙ exercise scientists conduct both basic and applied research ∙ research has been done on animals in ex.science

o treatments for asthma

o developing aritfical knees

o treatment of joint dislocation

o diabetes and exercise

 Chapter 2: Physiology of Exercise

 Skeletal Muscle

 -Comprised of groups of muscle fibers held together in fascicles  -Individual muscle fibers are individual cells with specialized structures  to generate tension that enable us to move

 -a skeletal muscle can contain hundred of thousands of cells  -each muscle cell has its own connection to the nervous system and its own blood supply

 -thin layer of connective tissue, the endomysium, wraps around each  cell If you want to learn more check out What are the antagonistic affectors?

 -at the ends of the muscle, the connective tissues taper and form  tendons, which attach the muscle to bone

∙ when a muscle cell generates tension, that tension is transmitted  through the connective tissue and tendon to the bone, resulting in  movement

The motor unit

          -muscle contraction can’t occur until the nervous system sends a  signal to the muscle  

Motor Neuron-single nerve cell, may innervate many muscle fibers Motor Unit-neuromuscular structure consisting of a single motor neuron and all the muscle fibers innervated by that neuron

∙ Motor neuon sends signal, all muscle fibers innervated by that  motor neuron are activated to generate tension

Inside the muscle cell

∙ myofibril-specialized component that generates tension and allows  us to create movement

o a muscle cell may contain hundreds to thousands of myofibrils ∙ sarcomere- repeating functional groups in myofibrils

o Contain 2 types of protein strands or filaments

 Thin myofilaments, composed of actin, are attached to  Z lines and extend into each sarcomere from both ends

 Thick myofilaments, composed of myosin, lie parallel to  the actin filaments and overlap them slightly at rest  

within the sarcomere

 Myosin filaments also have appendages called  

crossbridges that extend toward the actin  

filaments

∙ Z lines- protein filaments that separate sarcomeres

Sliding Filament Theory of Muscle Contraction

∙ muscle cell receives impulse from motor neuron

∙ crossbridges on myosin filaments attach to the actin filaments ∙ using energy generated within the muscle cell, the actin and myosin filaments move past each other, resulting in muscle contraction 3 Types of Muscle Action

∙ Concentric-movements in which a muscle shortens while generating tension

o ex: bicep curl (lifting to shoulders)

∙ Eccentric-movements in which a muscle lengthens while generating tension

o ex: bicep curl (lowering the barbell to starting position)

∙ Isometric-actions in which a muscle doesn’t change in length while  tension is being generated  

o ex: holding a barbell steady

Energy for Muscular Work

∙ chemical energy must be transformed into mechanical energy for  muscular work

∙ transduction-process by which energy is transformed from one form  to another  

 Energy Sources

∙ ATP in skeletal muscle cell can be used for movement (universal  energy source) (limited supply of ATP)

∙ Creatine Phosphate- stored in small amounts in the muscle cell  and is generated from ATP when the energy needs of the muscle  cell are low (limited supply of CP)

o when energy needs are high, CP can be used to regenerate  ATP

o creatine kinase transfers the chemical energy in CP to ATP ∙ Food (carbohydrates, fats, and protein) (large supply)

o chemical energy is measured in calories

o carbohydrates and fats are the 2 major sources of ATP  

regeneration for muscular action

∙ Glycogen and Glucose

o to maintain ATP for physical activity, muscle breaks down  glucose molecules w/ biochemical reactions

o Glucose molecules are stored in glycogen (in skeletal muscles  and the liver)

∙ Fats

o free fatty acid-usable form of fat within the body

o triglyceride –storage form of fat

o limited stores of triglycerides in the skeletal muscle cells, but  large stores are found in adipose tissue

o triglycerides are the major form of energy storage in the body  (1g of fat has twice the energy value of 1g carbs or protein) -when muscles need to generate more energy than is already available in the muscle fiber, glycogen and triglycerides are localized from storage  sites in the body, delivered to the muscle as glucose and free fatty acids, and converted to ATP in the muscle cells (which can be used to generate  muscular tension)

Energy Production

∙ Enzyme Systems- Enzymes are required to convert the energy  sources to ATP

∙ ATP needs enzymes to help release the energy for muscle  contraction

∙ Myofibrillar ATPase- enzyme located on the myosin crossbridge head that liberates the energy in ATP for the development of muscular  force

∙ aerobic energy transfer to ATP occurs in mitochondria, uses oxygen, and produces CO2

∙ anaerobic energy transfer to ATP occurs in the intracellular fluid and can produce lactic acid

∙ the selection of an energy source during exercise depends on the  supply of ATP and the rate that energy is needed

 Glycolysis-when glucose is used by muscle to generate ATP  (cytoplasm)

∙ anaerobic

∙ the majority of the chemical energy from glucose is transferred to  ATP through 2 more enzyme systems- Krebs cycle and electron  transport chain (mitochondria)

 Beta Oxidative Pathway-free fatty acids transfer energy to ATP ∙ located in mitochondria

∙ aerobic

∙ CO2 produced as a waste product

∙ cardiorespiratory system removes CO2 and delivers oxygen ∙ followed by Krebs cycle and ETC  

Muscle Fibers

∙ Type I-slow twitch, red muscle fiber, slow contracting, contains a  high amount of aerobic enzymes vs anaerobic enzymes, resistant to fatigue

o produces less force but for a longer duration

∙ Type II-fast twitch, white muscle fiber, fast contracting, high  concentration of anaerobic enzymes vs aerobic enzymes, produces  large amounts of force, quick to fatigue

o produces large forces quickly

∙ Myoglobin- protein that carries oxygen in the muscle tissue & gives  muscle its color

o Type I have more myoglobin than Type II

o Type II are white because of the lack of myoglobin

∙ Human muscle cells usually contain 50% of each type

o long distance runners tend to have a higher % of type I o short distance sprinters have a higher % of type II

Cardiovascular and Respiratory Systems

∙ connects tissues of the body to each other

∙ includes the heart, blood vessels, and blood

∙ Heart

o composed of cardiac muscle cells

o has 4 hollow chambers (2 atria and 2 ventricles) that fill with  blood

o when cardiac muscle contracts, blood is squeezed out of the  ventricles and forced into the blood vessels

∙ Circulation

o arteries, arterioles, capillaries, venules, and veins

o artery=away from heart

o vein=to heart

o capillaries connect arteries and veins, exchange of materials ∙ Blood

o transport medium

o consists of plasma, erythrocytes, leukocytes, and  

thrombocytes

o hemoglobin: blood protein that carries oxygen in RBCs ∙ Pulmonary Circuit- blood is pumped out of the right ventricle of the  heart through arteries to the lungs, where oxygen is delivered to the blood, and CO2 is removed from the blood. From there, the blood  travels through veins back to the left side of the heart ∙ Systemic circuit-blood pumped out of the hearts left ventricle  travels through arteries to the body’s other organ systems, where  materials are exchanged between tissue cells and the blood. From  these organ systems, the blood then travels through veins back to  the right side of the heart

∙ Cardiac output- the volume of blood that the heart pumps each  minute

o heart rate (# of beats per minute)

o stroke volume (the volume of blood pumped from the heart  during each beat)

o cardiac output = HR X SV

∙ Blood can be redirected from less active tissues to more active  tissues when needed

o Vasoconstriction-contraction of smooth muscle in arteriolar  walls  

o Vasodilation-relaxation of smooth muscle in arteriole walls o ^both of those work together to redirect blood flow ∙ Blood Pressure

o blood flow depends on movement of blood from an area of  high pressure to low pressure

o Systole- heart contraction, creates area of high pressure in  ventricles

o Diastole- heart relaxation, pressure in ventricles drops to 0 o measured with a sphygmomanometer (systolic/diastolic) o in aerobic exercise, systolic blood pressure increases, while  diastolic stays about the same

o in resistance exercise, both systolic and diastolic increase ∙ Respiratory System

o Gas exchange- transfer of oxygen and CO2 between the lungs and pulmonary capillaries

o VO2- variable used to express the amount of oxygen  consumed each minute

 determines the intensity and energy expenditure of  aerobic physical activity

o VO2 max test- measures an individual’s maximum aerobic  power or maximal aerobic capacity

 measures maximal amount of oxygen that an individual  can consume per minute

 used to predict athletic success in aerobic events

 individual walks or runs on a treadmill, gradually forced  to work harder and harder until the amount of oxygen  consumed reaches a plateau(which is the VO2 max)

o Lactate threshold-the point when lactic acid produced by the  body dramatically increases during intense exercise

 shows when the body is unable to use lactate as an  

energy source and remetabolize it in the liver as fast as  

it is being created in the muscle

 anaerobic

Chapter 3: Adaptations to Exercise Training

∙ Exercise training: participation in chronic, organized physical  activity, with the goal of improving athletic performance or specific  health and fitness parameters

∙ Specificity of training principle: a specific exercise elicits a specific  training response  

o the more the training stimulus resembles the performance  situation, the more powerful the training stimulus and the  greater effect it has

∙ Overload principle: improvements in performance capacity occur  when regular physical activity is increased above the level that the  performer usually experiences

o 3 factors that contribute to improved performance (overload)  frequency

 intensity

 duration

∙ each individual is different, so training strategies may need to be  customized to match the individual’s rate of improvement

 Anaerobic Training

∙ involves brief exercise activities at high intensity

∙ increases in muscular strength usually require exercise intensities of at least 30% of maximal voluntary contractile strength, or else there won’t be an adequate overload stimulus  

∙ Isometric exercise:  

o involve little or no change in joint position and muscle length o training response is specific to the angle at which the muscle  contraction is performed

o ex: isometric contractions of elbow flexors at 45 degree angle ∙ Dynamic Resistance Exercise:

o involves movement (repeated concentric and eccentric  muscle contractions)

o involve changes in muscle length and joint angles

o any stimulus that requires a moderate or high level of muscle  force repeated regularly induces an increase in muscular  

strength

o uses free weights, weight-training machines, or devices with  heavy rubber bands or springs

∙ Progress can be measured with 1 RM or 10 RM (amount of weight  that can be lifted 1 time or 10 times)

∙ Progress could also be measured with a machine that measures  force produced

∙ Measuring Anaerobic Power

o Margaria Power test

 individual runs as fast as possible up a series of steps,  

run is timed, and equations are used to determine how  

much power was performed

o Wingate test

 uses a stationary bike ergometer, individual performs a  30 second all-out effect on bike with a specific  

resistance

 provides a rough, indirect measure of energy capacity of the muscle’s ATP and CP systems

 Aerobic Training

∙ goal is to provide an overload stress to the aerobic systems ∙ Continuous training: an individual exercises at a low intensity for  a duration sufficient for creating an aerobic overload

o workload may be estimated as a % of max heart rate or % of  VO2 max

∙ Borg Scale: our sense of effort bears a close relationship to the  actual workload, our feeling correlates well with heart rate and VO2  max

 Interval Training

∙ Trains both aerobic and anaerobic systems

∙ alternates higher-intensity exercise bouts with rest periods ∙ more total work can be done by breaking it up than doing it  continuously

 Long-term Adaptations to Anaerobic Exercise Training

∙ Muscular Strength

o most of the gain in muscle strength occurs during the first  month or so of resistance exercise training  

o gains after occur much more slowly  

o major part of the initial gain involves the nervous system o increases in strength of individual muscle fibers occur due to  increases in size (hypertrophy) and increases in muscle fiber  number (hyperplasia)

∙ Training the Brain

o Merely thinking about performing a muscle contraction on a  regular basis can improve performance

 Long-term Adaptations to Aerobic Exercise Training  ∙ VO2 max increases with training

∙ Respiratory Adaptations

o lungs are more efficient at extracting oxygen from inhaled air  and exchanging it for CO2

∙ Oxygen-Carrying Adaptations

o concentration of myoglobin (important oxygen carrier in  muscles) increases, facilitating the delivery of oxygen to the  mitochondria

∙ Blood-Delivery Adaptations

o endurance training increases the size of the heart so it can  pump more blood each beat (higher stroke volume)

o total blood volume increases (helps with oxygen delivery and  regulation of body temp)

o increase in # of red blood cells means more hemoglobin  (more oxygen in blood)

o resting heart rate decreases in well-trained individuals  because the blood delivery system is more efficient at rest Energy Production Adaptations

∙ aerobically-trained individuals have more/larger mitochondria in  trained muscles  

∙ enzymes responsible for aerobic metabolism increase in  concentration and efficiency

∙ muscle contains more glycogen

∙ efficiency of beta-oxidation increases to better use fat stores for  energy

Anaerobic and Aerobic Training

∙ training aerobically may hinder anaerobic performance, and vice  versa

∙ myoglobin reduces with anaerobic but increases with aerobic ∙ # of mitochondria decreases with anaerobic but increases with  aerobic

∙ its hard to improve anaerobic and aerobic performance at once Detraining

∙ once training stops, the positive effects of resistance exercise or  endurance training wear off at about the same rate that training  occurred

Space (microgravity)

∙    extreme example of detraining 

∙ muscular atrophy (decrease by 20%) occurs because of no gravity  pulling on muscles and bones

∙ muscle strength decreases

∙ bone mass decreases

∙ special treadmills in spaceships to reduce these effects Overtraining

∙ too much training combined with inadequate rest periods can result  in decreased performance, reduced aerobic capacity, decreased  ability to store glycogen for ATP regeneration, weight loss, muscle  soreness, and higher resting and exercising heart rates ∙ immune system weakens

∙ women may become amenhorreic  

∙ bad for psychological health

∙ blood lactate is higher in exercise

∙ General Adaptation Syndrome: if rats were stressed and allowed to recover, they grew stronger. However, if they were repeatedly  stressed without time for recovery, they grew weaker.

Tapering: reducing training volume several weeks before a meet to  enhance performance

Chapter 9,12,13

Chapter 9: Intro to Biomechanics

∙ Eadweard Muybridge took pictures of animals and humans in motion -> led to development of modern tools for biomechanical analysis  and ‘motion capture’ technology

Biomechanics: The study of the human body at rest and

in motion using principles and concepts from physics, mechanics and  engineering 

∙ kinematics: a description of the temporal and spatial components of movement

o position or displacement

o velocity=displacement/time

o acceleration=velocity/time

∙ kinetics: the study of the forces acting on an object

o external forces (head injury)

o internal forces (muscle forces, bone on bone)

∙ together in gait lab: motion capture video provides kinematics, force plates provide kinetics in 3D

Why do we need biomechanics?

∙ to understand how the human body works

∙ to prevent injuries

∙ to optimize performance and efficiency  

∙ workplace & equipment design

Biomechanics of Injuries

∙ over/underpronation result in injuries while running

speed vs velocity

∙ speed: how fast an object travels

∙ velocity: how fast the object travels in a particular direction ∙ acceleration: difference in velocity over time

force: a push or pull exerted by one object on another

mass: the quantity of matter in an object, is a measure of the object’s  resistance to changing motion (acceleration)

 Newton’s Laws of Motion  

∙ Law of Inertia- an object at rest or in motion will continue in that  state unless acted upon by an outside and unbalanced force ∙ Law of Acceleration- F=ma

∙ Law of action-reaction- for every action there is an equal and  opposite reaction

o when you push down on the ground, the ground pushes back  on you  

impulse momentum relationship: a force applied to an object over a  known amount of time causes a change n the momentum of that object  ∙ Ft=(delta)mV

Gravity: -9.81m/s^2  

∙ center of gravity/center of mass-weight concentrated at a single  point

o changes with body position

o reaction board method: used to determine where the center of mass is located along the horizontal axis

∙

Contact forces

∙ Ground reaction force (GRF):the force exerted on the performer with the ground

o affects the vertical (up and down), anteroposterior (forward  and backward), and mediolateral (side to side) motion of the  object

o you can stand up against the force of gravity b/c of the GRF o force platform measures magnitude and direction of GRF o analysis of kinetics

Friction

∙ force that opposes sliding between 2 objects

Biomechanics of Running

∙ stride cycle

o swing phase: foot off the ground

o support phase: foot on the ground

o foot strike: foot-ground contact

∙ description of running speed

o stride length: length of one stride (2 steps)

o stride frequency (# of strides/sec)

∙ speed=stride length X stride frequency

∙ foot strike

o rear-foot strikers

o mid-foot strikers

∙ kinetics—what are the forces of?

o ground reaction forces

o joint torques

∙ good runners minimize vertical center of mass displacement (not  too much bouncing)

∙ center of pressure: instantaneous point of application of the  reaction force vector

o some people with diabetes have diabetic neuropathy and  can’t sense forces or pain in the soles of their feet

o we need to prevent diabetic ulcers

o use COP measurements to locate hotspots of high pressure  and design the shoe accordingly

Barefoot Running

∙ barefoot runners tend to run as midfoot strikers

∙ shod runners tend to run as heel strikers

∙ you can run as a midfoot striker in shoes

∙ biomechanists haven’t linked barefoot running to the prevention of  injuries with evidence, still testing the theory that barefoot running  will reduce injuries

∙ you can trade one injury profile for another if you aren’t careful Fluid resistance in cycling

∙ wind resistance: air is a fluid (fluid mechanics)

∙ velocity has a huge effect on the force or power required to  overcome air resistance (velocity could be from rider’s speed and/or the wind)

∙ modified position on bike to reduce frontal area  

 Chapter 12: sport psychology

∙ Study of the behavior, thoughts, and feelings of people engaging in  physical activity, exercise, sport, and athletic competition

∙ Coleman Griffith: first sport psychologist

o studied enhancement of psychomotor skill development and  relationship between personality and performance

Scope of Sport Psychology

∙ Cognitive Sport Psychology

o learning and skill acquisition

o attention

∙ Social Sport Psychology

o role of sport and competition in motor development o social facilitation

o competition and leadership

∙ Personality

o athletic personality

o traits

∙ Exercise Psychology

o runner’s high

o exercise adherence

o staleness

∙ Experimental Sport Psychology

o control heart rate with your mind?

o mental imagery or mental practice

∙ Psychometric Sport Psychology

o developments of measurements of instruments o perceived effort

o mood state

o motivation

∙ Clinical Sport Psychology

o work directly with individual to fix an issue

o “choking”

o exercise addiction

State vs. trait

∙ State-if you happen to be happy right now, that is your current state ∙ Trait-how you are described, more permanent than states Personalities Differ

∙ team sports vs. individual sports

∙ among different field positions (attackers are more emotionally  unstable and extroverted than defensive players)

∙ athletes in general  

o compared to nonathletes

o higher extroversion

o lower anxiety

∙ Not all evidence makes clear distinctions  

o elite and less-skilled wrestlers do not differ in personality  measures

Mental Health Model  

∙ successful athletes  

o have excellent physiology

o have excellent biomechanics

o also need excellent mental health

 to deal with yourself, others, and adversity

∙ short term-good mental health in training/competition

∙ long term-good mental health promotes athletic or sport longevity Profile of Mood States (POMS): Responses provide a T-score on key  characteristics that are compared to population norms

∙ Population norms: a large set of data from many people ∙ T-score: how far above or below the average you are

∙ Use POMS to address staleness

o staleness-a maladaptation to exercise

 a result of overtraining

 performance suffers  

 sleep problems

 loss of appetite

 psychological: depression, irritable

 physiological biomarkers: higher resting HR, stress  

hormones elevated

 weakened immune system

Arousal

∙ a state of heightened physiologic and psychological activity ∙ constantly changing based on the situation and environment ∙ optimal arousal isn’t necessary high arousal, it’s when you perform  the best

Yerkes-Dodson Law (Inverted U theory)

∙ Performance requires the optimal level of arousal

∙ inverted U varies in location and width for  

o different individuals  

o different sports

Mental Imagery

∙ use of visualization to perform a task only in the mind (no physical  movement)

∙ mechanisms

o psychoneuromuscular theory- (muscle memory)- imagery  duplicates a motor pattern in the brain but on a smaller scale,  activates same brain areas used in the real movement

o symbolic learning theory-more cognitive, thinking about task  more than movement (like a hockey goalie rehearsing the  response to different shots)

o arousal or activation theory- rehearsal places individual closer to right level of arousal (inverted U theory)

Anxiety

∙ state anxiety-a moment of high anxiety for a person (short term) ∙ trait anxiety-an anxious person, a personality characteristic (long  term but not necessarily permanent)

∙ controlling it

o meditation

o biofeedback

 provide person audio or visual feedback on HR, blood  pressure, muscle activity

 person can then try to control these physiological  

measures

∙ preventing it

o familiarization

 cross country team has 1 practice at the location of  state championships

 golf team practices on the upcoming tournament course

o rituals

 many elite golfers have a very specific pre-shot routine o imagery  

 you rehearse possible competition situations and a  

positive outcome

o experience and preparation

Biofeedback-process through which individuals control their own  physiologic processes using external, physical information

∙ heart rate

∙ blood pressure

∙ electromyogram-muscle activity

∙ galvanic skin response

∙ EEG (brain waves)

Exercise Psychology

∙ Exercise Adherence

o what makes a person stick with a program

 motivation

 self-efficacy

 proximity to exercise facility

 exercising in small groups

 knowledge of benefits

 avoiding too much too soon (soreness, failure)

 combining exercise with behavior modification programs

∙ Motivation

o what factors motivate a person for exercise

 extrinsic-when individuals engage in a certain behavior  to gain some external reward

 cash or a prize

 intrinsic-when individuals engage in behavior because  the individual enjoys the process and gains pleasure  

and satisfaction from participation

 exercise makes you feel good

∙ Self-efficacy

o how much does a person believe in their abilities

∙ Benefits

o what are the psychological benefits of exercise or physical  activity

Exercise improves

∙ anxiety

∙ depression

∙ psychological well-being

Central Governor Theory 

∙ central: brain and spinal cord

∙ peripheral: everything outside of that

What makes us stop exercising?

∙ central causes

o decrease in neural excitation to motor units

o cessation of motivation

o regulation from CNS to ensure catastrophe doesn’t occur ∙ peripheral causes

o build up of H+ ions

o inability of muscle to contract

o Ca2+ not being released from sarcoplasmic reticulum

o increased inorganic phosphate

Initial CGT Model

1. Anaerobic catastrophe model wasn’t enough

2. If peripheral skeletal muscles have a reserve left at ‘fatigue’, the  fatigue can’t come from peripheral control

3. There must be a central factor

            Teleoanticipation Model- 

∙    teleo=end, complete

∙    we subconsciously anticipate how long and hard the activity will be ∙    we make a plan to pace for the entire activity

∙    negative feedback allows us to alter this plan if we are in danger ∙    brain doesn’t determine performance, it regulates it

 Chapter 13: Neural Control of Movement

∙ Endocrine system (hormones) and nervous system (electrical) are  the 2 controllers of the body

∙ nervous system is faster controller

Peripheral Nervous System (PNS)

∙ receptors

∙ motor nerves  

∙ sensory nerves

Central Nervous System (CNS)

∙ Spinal cord

∙ brain

Afferent sensory pathways- receive information and relay it to the brain from the spinal cord (At the brain)

Efferent motor pathways- send signal from brain towards effectors  (muscles)

∙ synapse-neuromuscular junction

o when an action potential arrives at the presynaptic terminal  from the nerve axon, neurotransmitter acetylcholine is  

released

o Ach diffuses across the synapse to the muscle fiber  

membrane and a muscle fiber action potential is generated o synapses also form connections between neurons

How is the control of muscle fibers organized?

∙ muscle fibers are controlled in sets

∙ sets are stimulated by an action potential from a neuron ∙ a single neuron and all the fibers in innervates is a motor unit ∙ motor unit is called the final common pathway of control bc there is  

no further division of control; when an action potential reaches the  muscle fibers they all contract together

Parts of a motor neuron

∙ soma-cell body, has nucleus, receives input through dendrites ∙ axon-carries nerve impulses to terminal fibers which are connected  to muscle fibers at a synapse (in a motor unit)

Control Mechanisms at the motor unit level

1. Recruitment- increases and decreases in the # of motor units  involved in a task causes increases and decreases in muscular force ∙ motor neurons are recruited in order of size of soma

2. Rate Coding- if the firing rate (# of action potentials per second) of a neuron increases or decreases, this causes increases and decreases in  muscular force

Sensory Input-interaction between performer and environment ∙ requires integration of sensory information and motor activity o vision

o golgi tendon organs-detect tension (force) in muscle tendon  organ, inhibits motor neuron

o muscle spindles-detects changes in length of muscle  

o joint receptors-detect joint position

o cutaneous receptors

o vestibular system-canals that are filled with fluid respond to  accelerations of the head

Position Sense

∙ Proprioception- the detection of information about the movement  and orientation of your body in space

∙ Kinesthetic sense- sensation of movement

∙ Proprioceptors- sensory organs that are related to position sense To increase strength

∙ activate more motor units (recruitment)

∙ increase motor unit firing rate (rate coding)

∙ decrease antagonist activity

o strength gains are accompanied by increases in motor unit  firing rates

Bilateral Deficit- neural inhibition and muscular strength

∙ you would think that both legs together would be 2x the strength of  the individual legs, but it is not quite 2x as strong

∙ sum of unilateral strength scores is more than the single bilateral  strength score

∙ training in bilateral mode can result in dis-inhibition

-Fast neurons give a muscle fast properties, as slow neurons give a  muscle slow properties

∙ crossed innervation experiments take fast neurons and attach them  to slow muscles, gives the muscle fast properties

The role of the nervous system in strength

∙ crossed innervation experiments  

∙ timecourse of strength gains vs. timecourse of muscle hypertrophy;  strength gains occur before hypertrophy

∙ bilateral deficit- neural inhibition during bilateral contractions  modifiable with training

∙ mental imagery- some experiments have shown strength gains due  to mental practice of a task

∙ cross-transfer of strength gains. exercise the left arm and the right  arm becomes stronger

∙ increases in motor unit firing rates with strength gains

 The Brain

Motor cortex-neurons for the control of movement

Supplementary area- involved in planning and execution of complex  movements

Voluntary reaction time

1. stimulus received by receptor (eyes)

2. sensory cortex (visual)

3. motor cortex (choose action)

4. motoneurons at spinal segment

5. muscle

things that affect reaction time

∙ diverted attention

∙ # of stimulus response alternatives

∙ stimulus response compatability

Auditory is the fastest sensory modality

Simple reaction time -ex: sprinter and starters pistol

∙ fastest

∙ 1 stimulus=bang (auditory)

∙ 1 stimulus – response alternative=run

Choice reaction time- air force pilots

∙ understood in framework of information processing  

∙ more stimulus response alternatives: slower responses

Closed loop control-like a thermostat, senses the current temp and  either turns the heating unit on or off if the current temp doesn’t match the  desired temp. Takes time

∙ Proprioception- information about our movements and changes in the environments. then we adjust our movement accordingly while  it is still ongoing

Open loop control- fast movements, no time for adjustments based on  feedback