Chapter 5: Energy Expenditure & Fatigue

basal metabolic rate

rate of energy expenditure for an individual in supine position, measured in a thermoneutral environment immediately after 8 hours of sleep and at least 12 hours of fasting

Average range: 1200 - 2400 kcal/day

calorie

basic unit of heat

calorimeter

insulated, air-tight chamber that contain copper tubing throught which water is circulated. Heat produced by the body radiates to the walls and heats the water

direct calorimetry

measuring body's heat production to gauge the rate and quantity of energy production; uses a calorimeter

excessive post-exercise oxygen consumption

volume of oxygen consumed during the minutes immediately after exercise ceases that is above normally consumed at rest

fatigue

general sensations of tiredness and accompanying decrement in muscular performance; inability to maintain required power output to continue muscular work at a given intensity

Haldene transformation

an equation allowing one to calculate the inspired air volume from expired air volume or expired air volume from inspired air volume

volume of nitrogen inspired is equal to volume of nitrogen expired

indirect calorimetry

energy expenditure measured by measuring exchange of respiratory gases produced via oxidative metabolism (rates of O2/CO2 exchanged in lungs equals rate of their usage and release by body tissue)

lactate threshold

the point at which blood lactate begins to substantially accumulate above resting concentrations during exercise of increasing intensity

Normal levels 0.8-2.5 mmol/L

maximal oxygen uptake (VO2max)

maximal limit of one's ability to increase VO2 (aerobic capacity)

* Normally active untrained college-aged students = 38-42 ml/kg/min

peak oxygen uptake (VO2peak)

highest oxygen uptake achieved

respiratory exchange ratio

ratio between rate of CO2 release (VCO2) and oxygen consumption (VO2)

RER= VCO2/VO2; at rest=0.78 -0.8

resting metabolic rate

the bodys metabolic rate early in the morning following 8 hours of sleep

average total RMR of an individual engaged in normal daily activity = 1800-3000

Vo2 drift

a slow increase in VO2 during prolonged, submaximal, constant power output activity; observed well below lactate threshold, magnitude of increase of VO2 drift is much less than VO2max

How is RER used to determine oxidation of fats and carbohydrates

The amount of O2 used during metabolism depends on the type of fuel being oxidized; in general the amount of O2 needed to oxidize a molecule of CHO or Fat is proportional to the amount of carbon in that fuel. By finding how much CO2 molecules is released compared to amount of O2 released we can calculate RER

Carb: 1.0

Fat: 0.7

Protein: 0.82

How is maximal O2 uptake measured and what is its relationship to sport performance?

Vo2max can be estimated by submaximal and maximal test, direct and indirect calorimetry

Vo2max is a good predictor of success in endurance events and increases with training (5-20%). The more oxygen you can take in and use at higher levels, the more ATP you can produce through oxidative system, thereby delaying fatigue

Two possible markers of anaerobic capacity

blood lactate threshold: higher blood lactate threshold indicates being able to exercise for longer periods before fatiguing

EPOC: EPOC as an indicator of the amount of anaerobic activity that had occured (shows the amount of lactic acid in tissues, that needs to be removed in order to store depleted glycogen stores --> glycogen used in anaerobic glycolysis

How is lactate threshold measured and whats its relationship to sport performance

blood lactate samples; increases as intensity increases; reflects interaction between aerobic and anaerobic energy systems; ability to exercise at high intensities without accumulating lactate is beneficial to athletes because lactate accumulation contributes to fatigue; LT is major determinant of pace that can be tolerated during a endurance event

How is economy of effort measured and what is its relationship to sport performance?

no way to measure economy; high economy of effort mean using less energy during activity and therefore being able to exercise for longer periods of time

What is the relationship between O2 consumption and energy production?

O2 is required to breakdown substrates for energy; increased 02 consumption means being able to break down more substrate and being able to break down substrates quicker .:. being able to provide more energy for exercise and burning more calories

Why do athletes with high Vo2max values perform better in endurance activities than those with lower values?

ability to perform at a higher VO2max and being able to maintain VO2 max (or a % of Vo2max) for prolonged times indicates that the individual is able to take in more oxygen to be converted into energy for endurance activity

Possible causes of fatigue 1) 15-30 sec. and 2) 2-4 hours

1) PCr depletion, ATP decreasing, muscle glycogen depletion, possibly lactic acid accummulation --> increased muscle acidosis (increased H+), Failure of muscle fiber's contractile mechanism

2) glycogen depletion, increased muscle temperature, loss of water (dehydration) and electrolytes (high body T)

Three mechanisms through which lactate can be used as an energy source

1) can be taken up in mitochondria and directly oxidized

2) Lactate shuttle: transported to other cells for oxidization

3) transported by the blood to the liver, where it is reconverted into pyruvic acid

O2 and CO2 measurement volumes

expired O2 concentration is less than the inspired

CO2 concentrations are higher in expired air than in inspired

During O2 deficit, where does the body get the oxygen fro aerobic ATP production while O2 uptake is increasing?

O2 stores

Direct Calorimetry

Measurement of heat production as an indication of energy expenditure

Indirect Calorimetry

Calculates energy expenditure from ratio of CO2 produced to O2 consumed

All the body's metabolic process ultimately results in heat production. What are the percentages of substrate energy for ATP and heat?

________ % of substrate energy → ATP

________ % of substrate energy → Heat

40% and 60%

What are the pros of direct calorimetry?

Direct measurement and it is accurate

What are the cons of direct calorimetry?

Expensive, Not practical, Exercise equipment adds extra heat, Sweat creates measurement errors

What is the direct relationship in indirect calorimtery?

Direct relationship between O2 consumption & amount of body heat produced

How does indirect calorimtery calculate energy expenditure (EE)?

Ratio of CO2 produced to O2 consumed

What things are required to calculate VO2 and VCO2?

Volume of air inspired (VI)

Volume of air expired (VE)

Fraction of O2 in inspired air (FIO2)

Fraction of CO2 in inspired air (FICO2)

Fraction of O2 in expired air (FEEO2)

Fraction of CO2 in expired air (FECO2)

Respiratory Exchange Ratio (RER)

The ratio of Co2 production to the volume of O2 consumption

What are the RER values for fat and CHO?

Fat = _________

CHO = __________

Fat = 0.7

CHO = 1.0

What are the RER values at rest and during exercise?

At Rest: RER = _______ to _______

During Exercise: RER = _________ to > ________

At Rest: RER = 0.78 to 0.8

During Exercise: RER =0.7 to > 1.0

Metabolic Rate

The rate at which the body uses energy; it it based on whole-body O2 consumption and corresponding caloric equivalent

Basal Metabolic Rate (BMR)

The rate at which a person uses energy when the body is at rest.

Resting Metabolic Rate

Basal metabolic rate plus energy expended in digesting food

What factors directly relate to BMR?

FFM, Body surface area (BSA), age, body temperature, and stress

VO2max

Max amount of oxygen the body can take in and use during exercise

What are influencing physiological factors of VO2max?

-Maximum ability of CR system to deliver O2 to contracting muscles

-Muscle's ability to uptake O2 (Genetics and Training)

During the first few minutes of exercise, ___________ pathways initially contribute to production of ATP.

Anaerobic

Steady State

Balance between energy required and aerobic production of ATP

Oxygen Deficit

Refers to the lag in oxygen uptake at the beginning of exercise

What factors influence O2 deficit?

-Intensity of exercise

-Endurance Training Status

Who has a lower O2 deficit, a trained or untrained individual? Why?

Trained individuals have a lower O2 deficit (Better-developed aerobic bioenergetic capacity)

Oxygen Debt/EPOC

Excess O2 uptake above rest following exercise (Repayment for O2 deficit at onset of exercise)

What are some things that occur in the oxygen debt stage?

-Replenish depleted ATP & PCr stores

-Clear lactate produced by anaerobic metabolism

-Replenish O2 borrowed from hemo- & myoglobin

-Remove accumulated CO2

-Increase metabolic and respiratory rates due to increased body temperature

Maximal Oxygen Uptake

Greatest amount of oxygen that can be used at the cellular level for the entire body

Transition from ______________ to light/moderate exercise causes oxygen uptake to __________________ rapidly and steady state can be reached within _______________ minutes.

Rest; increase; 1-4

Failure of O2 uptake to increase instantly at start of exercise, shows ________________________ pathways contribute to the production on ________________ early in exercise.

Anaerobic; ATP

After steady state is reached, the body's ATP requirement is met via ________________________ metabolism.

Aerobic

Lactate Threshold

The point at which blood lactate accumulation increases markedly above resting levels

Economy of Effort

being efficient w/ your body; minimizing energy expenditure

What are some characteristics of successful endurance athletes?

High VO2max, High lactate threshold, High economy of effort, High % type I muscle fibers

What 3 substrates power muscular contractions?

ATP, PCr, and Glycogen

What mechanisms influence fatigue? (Hint. 4 mechanisms)

-Type & intensity of exercise

-Muscle fiber type

-Training status

-Diet

What are the major causes of fatigue?

-Inadequate energy delivery/metabolism

-Accumulation of metabolic by-products

-Failure of muscle contractile mechanism

-Altered neural control of muscle contraction

Of the major causes of fatigue which are peripheral factors?

-Inadequate energy delivery/metabolism

-Accumulation of metabolic by-products

-Failure of muscle contractile mechanism

Of the major causes of fatigue which are central factors?

Altered neural control of muscle contraction

Glycogen Depletion

"Hitting the wall"; used more rapidly during the first few minutes of exercise

What factors contribute to glycogen depletion?

-Fiber type & recruitment

-Involved muscle groups

-CHO Source

What are the 4 metabolic by-products?

Pi, heat, lactic acid, and hydrogen ions

______________ glycogen is insufficient for prolonged exercise.

Muscle

________________ glycogen is used to provide a constant supply of blood glucose.

Liver

What happens to the blood glucose when muscle uptake exceeds the liver's glucose output?

Blood glucose decreases = hypoglycemic

As muscle glycogen decreases, liver glycogenolysis ___________________.

Increases

Fatigue may result from depletion of _______________ or glycogen, which impairs ____________ production

PCr; ATP

__________ generated by lactic acid leads to fatigue by ________ muscle pH, impairing cellular processes of ____________ production and ______________.

H+, decrease; energy production; muscle contraction

What are the theories why the neuromuscular junction fails and prevents muscle activation?

-↓ ACh synthesis & release

-Altered ACh breakdown in synapse

-↑ in muscle fiber stimulus threshold

-Altered muscle resting membrane potential

What is Excess Post-Exercise Oxygen Consumption? What is an alternate name fro EPOC?

O2 consumption does not decrease and return to resting levels immediately after exercise, the extra O2 consumed after exercise is called EPOC

aka oxygen debt

Describe the five criteria that indicate a valid VO2 max test result.

1) plateau in O2 consumption

2) the attainment of a RER reading of 1-1.5 or greater

3) the attainment of age-predicted max HR

4) the exhaustion of the subject

5) blood lactate 8mmol/L or greater

How does the lactic acid production affect exercise performance?

Decrease pH in the muscle cell causing reactions to occur slower.

The more lactic acid and athlete can produce the greater the power output the athlete can generate

-fast twitch muscle uses fast glycolysis

contributes to muscle fatigue

How does the body respond during steady state prolonged exercise compared to prolonged exercise in hot or humid environments?

steady state:

-ATP production primarily from aerobic systems

-steady state O2 uptake can generally be maintained during sub maximal exercise

hot or humid:

-upward drift of O2 uptake over time

-due to body temp and rising epinephrine and norepinephrine

-increasing body temp = increasing energy metabolism

What is the difference between lactate and lactic acid?

Lactate is the conjugate base of lactic acid

What is the metabolic equivalent or MET?

how does 1 MET correspond to VO2?

The expression of energy cost for activities in a simple unit.

1 MET = 3.5 ml/kg/min (relative VO2)

Describe the changes that occur in energy metabolism (ATP production) and O2 uptake when transitioning from rest to exercise.

1-ATP production increases immediately (quicker if fit)

2-oxygen uptake increases rapidly

-reaches steady state in 1-4 min

-after steady state is reached ATP met through aerobic systems

3-initial ATP production met through anaerobic pathways (less if fit)

-ATP-PCr System

-Fast Glycolysis (less lactic acid if fit)

4-oxygen deficit

-delay in oxygen uptake at the beginning of exercise

Discuss what happens to lactate during EPOC

70% in oxidized

20% reconverted to glucose

Slow curve concerned with blood glucose

What causes the lag in oxygen uptake at the onset of exercise?

Studies suggest that the lag is due to the slowness of oxidative phosphorylation to increase ATP production immediately

How can the lactate threshold be utilized in exercise training programs?

Prediction of performance along with VO2.

Used to plan training programs as a marker of training intensity.

At rest, most ATP is produced via which metabolic pathway? How would you characterize blood lactate levels at rest?

-Almost 100% from aerobic pathway

-Blood lactate less than 0.1 mmol/L

Outline steady state

Physiological variables are constant but not necessarily normal. Steady state can be disrupted if in a hot and humid environment.

What is the typical relative VO2 at rest?

3.5 ml/kg/min

0.25 L/min

How does O2 deficit differ between trained and untrained subjects? What factors account for this?

trained:

-reach steady state quicker

-less lactic acid accumulation

-shorter recovery

-better developed aerobic bioenergenic capacity

untrained:

-takes longer to reach steady state

-use more fast glycolysis = greater O2 deficit

-longer recovery

-more lactic acid

What is the typical absolute VO2 for an individual?

0.25 L/min

What two factors effect EPOC?

Lactate removal and elevated hormone levels

Why do trained individuals produce less lactic acid than untrained individuals?

Better developed aerobic bioenergenic capacity due to cardiovascular or muscular adaptations

What are the two sources of CO2 during exercise?

Metabolism and H+ buffering system

What does VO2 measure? What are two ways in which VO2 is expressed?

-The amount of oxygen the body consumes. The ability to deliver and use oxygen.

-absolute: in L/min

-relative: in ml/kg/min

The measure regarded by most as the best single measurement of cardiorespiratory endurance and aerobic fitness is known by all of the following terms EXCEPT

a. VO2max

b. VO2 drift

c. maximal oxygen uptake

d. aerobic capacity

b. VO2 drift

Delayed Onset Muscle Soreness

Feelings of muscle stiffness experienced in the days following exercise (48 hours)

Decrease exercise intensity and duration; stop exercise if necessary. Pick two that apply.

a.Acute muscle soreness

b.DOMS

c.EAMCs

a and c

Ensure good conditioning based on the principle of progressive overload. Pick two that apply.

a. Acute muscle soreness

b.DOMS

c.EAMCs

a and c

Hydrate properly with fluid and electrolytes.

a. Acute muscle soreness

b. DOMS

c. EAMCs

c

Perform high-intensity exhaustive training bout at the start of the training program.

a. Acute muscle soreness

b. DOMS

c. EAMCs

b

Reduce the eccentric components of training.

a. Acute muscle soreness

b. DOMS

c. EAMCs

c

Regularly stretch the affected muscles.

a. Acute muscle soreness

b. DOMS

c. EAMCs

c

What is NOT thought to be associated with DOMS?

a. Intracellular calcium level increases and activates enzymes that destroy the z-lines.

b. The by-products of cell breakdown and the inflammatory response stimulate free nerve endings.

c. High tension in the contractile-elastic component of muscle results in structural damage.

d. Loss of spinal-reflex control of alpha motor neurons during eccentric exercise over-stimulates muscle fibers, resulting in damage.

d

Which of these is NOT true of delayed-onset muscle soreness (DOMS)?

a. In the short term, DOMS reduces the force-generating capacity of the affected muscles.

b. DOMS is likely necessary to maximize the training response

c. Intense concentric exercise is the most likely cause of DOMS.

d. DOMS may actually result from structural damage in the muscle.

c