Human Energy Expenditure During Rest & Physical Activity: Chapter 11

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Individual variability in energy transfer underlies the concept of

individual differences

- Encompasses specificity and generality

For example, a high VO2max in one activity does not ensure a similarly high VO2max in a difference activity. This is an example of what

Specificity principle

For example, some individuals with a high VO2max in one activity possesses above average VO2max in another similar activity. This is an example of what

Generality principle

If there is a high degree of _____ exists in energy transfer capacity and exercise performance requiring different energy systems

specificity

A high degree of specificity exists for the effects of physical training on

neuromuscular patterning and metabolic demands

Specificity indicates a low likelihood for an individual to excel in

each of a particular sport's sprint, middle distance and long-distance categories

Immediate and short term energy systems

- Power for up to 2-3minutes of duration

- Anaerobic energy mainly powers fast, short-duration movements or when increasing resistance to movement at a given speed

- When the movement begins at a fast or slow speed, the intramuscular high-energy phosphates ATP and PCr provide immediate energy for muscle action

- Following the first few seconds of movement, glycolytic pathways generate increasingly more of the energy requirements

When is the immediate energy system used?

In movements 6-10seconds

- Rely exclusively on energy from the intramuscular high-energy phosphates

When is the short term energy system used?

In movements 2-3min long

When is the long term energy system used?

In movements greater than 3min

Two assumptions about performance tests to evaluate the immediate energy system

1. All ATP at maximal short-term power output regenerates via ATP-PCr system

2. Adequate ATP and PCr exists to support maximal performance for about 6-10 seconds

What are examples of performance tests to evaluate the immediate energy system?

- Stair-sprinting power test

- Vertical jump & reach test

- Standing broad jump

- Sprint cycling

- Cycling

- Shuttle runs

- Arm cranking

- Power is being measured

Physiologic tests to evaluate the immediate energy system

Measures that evaluate energy-generating capacity the immediate energy system depend upon two factors

- Size of the intramuscular ATP-PCr pool

- Depletion rates of ATP and PCr in all-out, short duration exercise

ATP and PCr depletion rates provide a direct estimate and correlate highly with performance assessments of which energy system?

Immediate energy system

- Nearly impossible to obtain such precise biomechanics data during all-out exercise of brief duration

Short term energy system

- When the energy requirement great exceeds energy generated by hydrogen oxidation in the respiratory chain

- Glycolytic production of ATP predominated with subsequent quantities of lactate accumulating in active muscles and blood

Blood lactate levels provide the most common indicator of

activation of the short-term glycolytic energy system

Performances that activate the short-term energy system require

maximal exercise for up to 3 minutes

What are examples of exercises that would activate the short-term energy system?

- All out runs

- Stationary cycling

- Shuttle runs

- Repetitive weight lifting at a given % of max

What type of performance test should be used to evaluate the short term energy system?

Wingate test

- 30s supermaximal effort on bike

Anaerobic step test

MOAD test

Wingate test performance measures include

1. Peak power: highest mechanical power generates during any 3-5sec period (measure of high-energy phosphates)

2. Relative power: peak power divided by body mass

3. Anaerobic fatigue: percentage decline in power output during the test

4. Anaerobic capacity: total work accomplished over the 30 seconds (measure of anaerobic capacity and reflects glycolytic capacity)

How does age impact performance on the wingate test?

Children perform poorly compared to adolescence and young adults because

- they have lower intramuscular glycogen concentrations

- poorer motivation

- slower rate of glycogen hydrolysis

How do genders have different anaerobic capacities?

Due to the fact that

- Males have a greater muscle area

- Greater metabolic capacity of fast twitch fiber type

- Larger catecholamine response to physical activity

Maximally accumulated oxygen deficit

Another indirect measure of anaerobic metabolic capacity

- thought of as the GOLD standard

- calculated as the difference between supra maximal oxygen consumption at 125% of subjects directly measured VO2 from exercise intensity-oxygen consumption during a 2-3 minute all out treadmill run to fatigue

- provides an estimate, able to differentiate between aerobically and anaerobically trained individuals

What provides the most common indicator of activation of short-term energy system?

Blood lactate level

Glycogen depletion rate

- Depletion pattern can reveal glycolytic contribution (glycogen stored in specific muscles activated by exercise) to power the short-term energy system

- Glycogen, the stored macronutrient that most rapidly phosphorylates ATP, serves as the only macronutrient that anaerobically resynthesizes ATP

Three factors that contribute to differences among individuals in their capacity to generate short-term anaerobic energy

1. Effects of previous training

2. Capacity to buffer acid metabolites

3. Level of motivation

Effects of previous training

Higher levels of muscle lactic acid, blood lactate and more pronounces muscle

Capacity to buffer aid metabolites

- How well different substrates resist increase in free hydrogen ion concentration by binding protons to prevent a decrease in ph

- Anaerobic training might enhance short-term energy capacity by improving the body's alkaline reserve for buffering

Level of motivation

- Higher pain tolerance, toughness, or ability to push through discomfort

What are the determinants of endurance performance?

- VO2max

- Capillary density

- Enzyme level based on available oxygen (how much lactic acid is being accumulated)

- Mitochondrial size and number

- Muscle fiber type

_____ represents a fundamental measure of physiologic functional capacity for physical activity aka gold standard

VO2max

True VO2max assessment

- A leveling off or peaking over in VO2 with increasing exercise intensity

- Generally provides assurance that a person has reached maximum aerobic metabolism

VO2 peak

- Highest value of oxygen consumption measured during a graded exercise test

- Applied when leveling off does not occur or maximum performance appears limited

- Secondary criteria include attainment of age-predicted maximum heart rate

What are difference maximal oxygen consumption tests?

- Usually include treadmill running or walking

- Bench stepping

- Stationary cycling

Maximal oxygen consumption tests can be

A single continuous 3-5 min supra maximal effort or progressive increments of effort

- Usually consists of progressive increments in grades exercise and effort

- Termination of test influenced by motivational factors

- Bringing the subject to the point of acceptable criteria for either a max or a peak often required urging

What are the 2 types of VO2max test protocols?

- Continuous

- Discontinuous

Continuous VO2max test protocol

- Progressively increasing exercise increments without recovery or rest intervals

- Provides a practical test of aerobic capacity for most healthy individuals

- Total time for test should be 8-10min

Discontinuous VO2max test protocol

- Progressively increasing exercise increments interspersed with recovery intervals

- Total time for test averages 65min

- Better choice for reconditioned persons who cannot perform progressive exercise increments continuously

Naughton test

Discontinuous

Astrand test

Continuous

Bruce test

Continuous

Balke test

Continuous

Ellestrad test

Continuous

Harbor test

Continuous

List the factors that affect maximal oxygen consumption

What are the factors that affect maximal oxygen consumption?

1. Mode of exercise: Treadmill exercise produces the highest values

2. Heredity: Average contribution about 20-30%

3. State of training: Average contribution about 5-20%

4. Gender: Women score 15-30% below male values

5. Body size and composition: Body mass variations explain up to 70% of differences among people

6. Age: Declines after age 25 at a rate of 1% per year

Aerobic capacity prediction: Walking test

- Predicts with reasonable accuracy

- 1 mile walk test

- Measure time it takes to walk 1 mile

- HR is measured immediately at the end of the late quarter mile

- Relatively low SEE

- 30-69 years old

- Considers body weight, gender, and age

- Put variables into an equation and compare to normative values

Aerobic capacity prediction: Endurance runs

- Assumes that ability to maintain a high, steady rate VO2 largely determines the distance run performance

- 12min run

- VO2max predictions based on running performance should be viewed with caution

- SEE averages about +_8 to 10% of predicted value

- Doesn't consider age and body mass

Predictions based on HR

- Linear relationship between HR and VO2max

- Slope of line and draw a line of best fit

- VO2max from sub maximal HR fall within +-10-20% of persons actual VO2max

- Not used in research but can be used in the clinic

A person with the smallest HR tends to have the

highest exercise capacity and highest VO2max

A faster recovery HR corresponds to

a higher VO2max

HR recovery tests to assume VO2max

- Forestry Step test (5min)

- Queens College Step test (3min)