APK 4134

Acute exercise (def and example)

a single bout of exercise

ex: running on a treadmill for an hour or lifting weights

Acute response to a single bout of exercise

body's immediate response to, and sometimes its recovery from, a single bout of exercise

Chronic adaptation

how the body responds to the stress of repeated exercise over a period of days, weeks, & months

Ergometer

(Ergo \= work; meter \= measure)

an exercise device that allows the intensity of exercise to be controlled (standardized) and measured

\_____________ and \________ ergometers are most commonly used due to
-Cost
-Comfortability
-Specificity (other ergometers)

Treadmills ; cycle

Other ergometers

allow athletes who compete in specific sports or events to be tested in a manner that more more closely approximates their training and competition

Example of other ergometer \#1

arm ergometer

may be used to test athletes or non-athletes who primarily use their arms and shoulders in physical activity

Example of other ergometer \#2

swimmers

Two basic types of research design

Cross-sectional
Longitudinal

Cross-sectional research design

cross section of the population of interest tested at one specific time, with differences between subgroups to be compared

Longitudinal research design

same research subjects are retested periodically after initial testing to measure changes over time (often more accurate)

Dose-Response Relation

the higher the "dose" of exercise training, the higher the resulting concentration of HDL-C.

Cross-sectional research design use/cons

best for identifying dose-response relationships, establishing group differences for further exploration

Cons: may be influenced by too many factors (differences in genetic factors, diet, etc.)

Longitudinal research design use/cons

best for studying changes in variables over time (diet and other variables more easily controlled)

Cons: time-consuming, expensive, not always possible

Confounding Factors in Exercise Research

•Temperature
•Humidity
•Noise
•Food intake
•Sleep
•Time of day
-Diurnal variation

Diurnal variation

fluctuations that occur during a 24-hour day

Control group

Critical to have

Acts as a comparison group

Makes certain that any changes observed in a training group are solely due to the training program and no outside factors

Placebo group

Important to have so if this group and the intervention groups improve their performance to the same level, then the improvement is likely the result of the placebo effect.

If that happens then we can conclude that the intervention does not improve performance

Crossover design

can help control for placebo effect

each group undergoes both treatment and control trials at different times

Smooth muscle

involuntary, single nucleus, non-striated

•Hollow organs (blood vessels, digestive tract)

Cardiac muscle

involuntary, single nucleus, striated (\= has sarcomeres)

•Heart

Skeletal muscle

voluntary, striated, multinucleated

Most muscles you probably think of
Skeleton

Anatomy of skeletal muscle

•Epimysium
-Surrounds entire muscle
-Consists of many bundles (fasciculi)

•Perimysium
-Surrounds fasciculi (fascicle)
-Fascicle consists of individual muscle cells (muscle fibers)

•Endomysium
-Surrounds muscle fibers
- Consists of myofibrils (thick and thin filaments) divided into sarcomeres
-Can be up to 12 cm long!!

Myofibrils

-Muscle -\> fasciculi -\> muscle fiber -\> myofibril

-Hundreds to thousands per muscle fiber

-Made up of sarcomeres

Sarcomeres

Basic contractile element of skeletal muscle

Composed of actin (thin filament) and myosin (thick filament)

Transverse tubules (T-tubules)

Extensions of sarcolemma that pass through fiber

Carry action potentials (nerve impulses, cause muscle contraction) along cell

Sarcoplasmic reticulum (SR)

Ca2+ storage (crucial for muscle contraction)

Satellite cells

Muscle growth, development-Response to injury, immobilization, training

Thick Filament

Myosin

•Two intertwined filaments with globular heads
-Will interact with actin filaments for contraction

•Stabilized by titin

Thin Filament

Actin

Contains three proteins

-Actin: contains myosin-binding site
-Tropomyosin: covers active site at rest
-Troponin: anchored to actin, binds Ca2+, which moves tropomyosin and unlocks myosin-binding site so that contraction can occur

Sliding Filament Theory

during muscle contraction myosin cross bridges are activated
they bind with actin
myosin heads rotate
pushing thin filament (actin) toward center of sarcomere (M Line)

this shortens the sarcomere and shortens the muscle

Dendrites

-Receives cell processes
-Carry impulse toward cell body

motor unit

Single alpha-motor neuron + all fibers it innervates

More motor units recruited \= more contractile force

go over excitation and contraction coupling notecards

Energy for Muscle Contraction

Muscle contraction requires energy (ATP)

ATP binds to myosin head, causing contraction
-Myosin detaches from active site (by binding of ATP)
-ATPase on myosin head splits ATP
-ATP -\> ADP + Pi + energy
•Energy is used to power the tilting of the myosin head (power stroke)
-Myosin head rotates back to original position (through splitting of ATP)
-Myosin attaches to another active site farther down

Muscle Fiber Types

Type I (aerobic)
Type IIa (anaerobic)
Type IIx (anaerobic)

type I

slow twitch

Slow contraction, used for aerobic activities, force production is low but is very resistant to fatigue, appear dark in color (capillaries and blood flow)

type IIa

fast twitch oxidative-glycolytic

Fast contraction, used for longer anaerobic activities, force production is high but not fatigue-resistant

-More force, faster fatigue than type I
-Short, high-intensity endurance events (1,600 m run)

type IIx

fast twitch glycolytic

Fastest contraction, used for short anaerobic activities, force production is very high but not fatigue-resistant, appear white in color (low blood flow, low capillarization)

-Seldom used for everyday activities
-Short, explosive sprints (100 m)

type 2 fibers in general

Efficiently produce ATP from fat, carbohydrates

Poor aerobic endurance, fatigue quickly

Produce ATP anaerobically

Most people are born with about 50% Type I and 50% Type II fibers BUT...

...some people are not

The people that have the greatest imbalances are often those who are professionals in sport

What type (1 or 2) of muscle is the soleus? hint: its the same in everyone.

type I

How Do We Determine Fiber Types?

Speed of myosin ATPase

Muscle biopsy
•Small (10-100 g) piece of muscle removed- Frozen, sliced, examined under microscope

Fast myosin ATPase \=

fast contraction cycling (Type II)

Slower myosin ATPase \=

slower contraction cycling (Type I)

SERCA pump is slower in \_______

Type I (takes longer to pump Ca2+ into sarcoplasmic reticulum)

Type \____ fibers have a more highly developed sarcoplasmic reticulum

II

3 to 5 times faster Ca2+ release

Type I motor unit

smaller neuron and cell body

Type II motor unit

larger neuron and cell body

\>300 fibers

Difference in force production between Type I and Type II motor units due to:

Type II fibers tend to be larger in size than Type I

Type II motor units can produce more force due to number of fibers

Order of recruitment of motor units related to size of a-motor neuron

Recruit minimum number of motor units needed depending on intensity

1st - Smallest (type I) motor units
2nd - Midsized (type IIa) motor units
3rd - Largest (type IIx) motor units

Dynamic contraction (action)

Muscle produces force and changes length

Joint movement produced

Isometric (Static) contraction (action)

Muscle produces force but does not change length

Joint angle does not change

Myosin cross-bridges form and recycle, no sliding

cOncentric contraction

Most familiar type of contraction

Muscle SHORTENS while producing force

Sarcomere shOrtens, filaments slide toward center

Ex: during a bicep curl, the biceps

Eccentric contraction

Muscle LENGTHENS while producing force

Cross-bridges form but sarcomere lEngthEns

Ex: lowering the weight when doing a bicep curl

How do we increase force production?

Increase the frequency of stimulation

--\>Increasing the amount of signals sent to the muscle telling it to contract

Make sure muscle is at an optimal length

twitch

smallest contractile response of a muscle fiber to a single electrical stimulus

summation

series of twitches in rapid succession, increases force because each builds off the previous

tetanus

peak force of the muscle fiber or motor unit as a result of multiple twitches in succession

Length-tension relationship

Optimal sarcomere length \= optimal overlap

Too short or too stretched \= little or no force develops

Speed-force relationship (Force-Velocity Curve)

Force production is inversely related to velocity of shortening

As force increases, velocity decreases

Concentric contractions (esp. at high speeds) produce the \_______ forces

lowest

Think: how much weight you can lift on a squat

maximal force development DECREASES at higher speeds

Eccentric contractions produce the \_______ forces

largest

Think: how much weight you can lower on a squat

maximal force development INCREASES at higher speeds

Metabolism

sum of all chemical reactions in the body (including catabolism and anabolism)

Catabolism

breaking down

Nutrients are broken down to salvage their components or to generate energy

Ex: carbohydrates in diet -\> glucose in the blood

Anabolism

building up

Biomolecules are synthesized from simpler components

Ex: glucose in blood glycogen in muscles

Substrates (macronutrients)

-Fuel sources from which we make ATP
-Carbohydrate, fat, protein

Resting uses

50% carbohydrate, 50% fat

Exercise (short, high-intensity) uses

carbohydrate

Exercise (long, low-intensity) uses

fat

All carbohydrates ultimately converted to \_________ by the \_______

glucose; liver

What is the primary ATP substrate for muscles & brain?

glucose

can be used for energy ("glucose pool")

Glycogen

the storage form of carbs

Extra glucose (~2,500 kcal) stored in body as glycogen in the liver and muscles in a process known as \__________________

glycogenesis

insulin

released due to a rise in blood glucose

causes glucose to be taken up by cells

**ANABOLIC**
because when insulin is released into the bloodstream, it acts to shuttle glucose [carbohydrates], amino acids, and blood fats into the cells of the body.

Once glycogen storage tanks are full, extra glucose is then stored as \____________________ (fat) within body and within muscles

triglycerides

Glycogenolysis

the process of glycogen being converted back to glucose when needed to make more ATP

Glycogen depletion leads to ...

fatigue

Glycogen stores are limited to \_______kcal

2500

Are there greater amounts of glycogen stored in the muscles or in the liver?

the muscles

the liver

can help maintain glycogen levels when they get low and acts as a "glycogen reservoir"

Glycogen in muscle

can be used for exercise, but it cannot borrow glycogen from other muscles

Fat (triglycerides)

3 fatty acids placed on a glycerol backbone

Efficient storage
+70,000 kcal stored in body
Unlimited fat storage

prolonged, less intense exercise

-HIGH net ATP yield but SLOW ATP production
-Triglycerides must be broken down into free fatty acids (FFAs) and glycerol
-Only FFAs are used to make ATP

lipolysis

Stored fat can be broken down into FFA

lipogenesis

the process of converting protein into fatty acids

Body protein can be used as an energy substrate during starvation or intense training

-protein breakdown
-gluconeogenesis

gluconeogenesis

the process by which protein or fat is converted into glucose

proteins can also convert into \____________

Free Fatty Acids

-For energy storage
-For cellular energy substrate

Energy is produced at a controlled rate based on: \______&\______

availability of primary substrate & enzyme availability

Excess of given substrate \= cells rely on that energy substrate more than others

Enzymes

Control rate of energy release

Do NOT start chemical reactions or set ATP yield

Do facilitate breakdown (catabolism) of substrates
- faster breakdown

suffix: -ase

Rate-limiting enzyme:

-Controls rate of overall reaction
-Activity influenced by negative feedback

Negative feedback and examples

the end product of a process in turn reduces the stimulus of that same process

Exs:
an increase in the product of a reaction slows down the overall reaction

Buildup of product (ATP) inhibits ATP production

ATP + water + ATPase -\>

ADP + Pi + energy

ADP

lower-energy compound, less useful (2 phosphates)

ADP can later be used to reform ATP

Three ATP synthesis pathways:

-Phosphagen (ATP-PCr system)
-Glycolytic system
-Oxidative system

Phosphagen (ATP-PCr) system is: (anaerobic/aerobic)

anaerobic

Glycolytic system is: (anaerobic/aerobic)

anaerobic

Oxidative system is: (anaerobic/aerobic)

aerobic

All systems convert \___ to \___

ADP to ATP

Phosphagen system relies on what to deliver energy?

stored phosphocreatine (PCr)

PCr acts as a 'reservoir' of high-energy phosphate bonds