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Unit 10 > Week 4: Exercise physiology Lecture > Flashcards

Week 4: Exercise physiology Lecture Flashcards

1
Q

Define Metabolism

A

The sum of chemical reactions that occur within a living organism in order to maintain life.

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2
Q

What is the physics law relating to energy?
How does this relate to the body?

A

Energy can not be created or destroyed only transformed from one form to another.
The same is true for biochemically active molecules

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3
Q

Define cellular respiration

A

The chemical breakdown of organic molecules to produce energy in the form of ATP

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4
Q

How do we measure the rate of energy production by the body?
What is the drawback of this?

A

Use metabolic rate
This is estimated by oxygen consumption - however, this assumes pulmonary oxygen is equal to the oxygen uptake to the tissue - however, this is not always true such as in anaerobic respiration.

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5
Q

Why is respiratory quotient important?

A

The metabolic rate is determined by the substance/nutrient used to contribute to energy production
The respiratory quotient (RQ - cellular level)) or respiratory exchange ratio (RER - lung level) can be used to infer the substrate being used.

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6
Q

What is the respiratory quotient?

A

The ratio of carbon dioxide formed for each molecule of oxygen consumed at the cellular level, in the usage of a certain subtrate in metabolism.

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7
Q

What respiratory quotient value indicates what substrate?

A

1 - carbohydrates
0.8 - protein
0.7 - fats (less CO2 than O2)
A mixed diet will give a mixed value.

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8
Q

What is the respiratory exchange ratio?

A

The output of carbon dioxide by the lungs divided by the uptake of oxygen during the same period.

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9
Q

What is indirect calorimetry?
What is its function?

A

Also known as expired gas analysis - surrogate measure of metabolism at peripheral tissue (skeletal muscle)
Uses fractions of CO2 and O2 expired and respiration rate to assume oxygen consumption hence metabolism
Quantifies heat loss to metabolism.

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10
Q

What variables need to be adjusted for in indirect calorimetry?

A

Ambient temperature, pressure and humidity - as these all influence gas volume
Hence values should be adjusted as if for a dry gas.

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11
Q

What is meant by a steady state of metabolism?

A

The assumption that oxygen intake and the lungs it equal to oxygen consumption in the peripheral tissues.

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12
Q

Define metabolic rate

A

The rate of energy production by the body.

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13
Q

What is the equation for aerobic respiration?

A

Glucose C6H12O6 + 6O2 —-> 6CO2 + 6H2O + heat/energy/ATP

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14
Q

What is the relationship between oxygen consumption and energy?

A

One litre of oxygen consumption is equal to 5kcal burnt.

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15
Q

What indicates metabolic thresholds?

A

Also called lactate threshold, ventilatory threshold or anaerobic threshold.
Change from aerobic to anaerobic metabolism
Increase in blood lactate concentration, changes in ventilation, onset of fatigue.
Above this threshold, a steady state may not be reached

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16
Q

What is the resting metabolic rate?

A

The amount of energy needed to maintain homeostasis or normal physiological function, typically determined by lean mass
Includes: brain function, control of body temperture, blood circulation and breathing

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17
Q

What makes up the total energy expenditure/ bodies metabolic rate?

A

Resting metabolic rate - 60-70%
Diet-induced thermogenesis - 10% - influenced by the amount and type of food, used to absorb transport and use food.
Physical activity - 30%, varies by activity of the person. Can be incidental or active.

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18
Q

What factors influence the resting metabolic rate?

A

Age (loss of muscle tissue, change in neurological tissue, children more energy to maintain body temp)
Sex (males larger in size and greater proportion of muscle mass)
Growth
Lean body mass v fat
Hormones
Genetics
Physiological stresses
Pregnancy
Temperature
Dieting or starvation.
Drugs - nicotine and caffeine
Illness - increase as need to recreate tissue

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19
Q

What foods have the greatest effect on diet induced thermogenesis?

A

Protein - increases the most
Carbohydrates
Fats - increase least.

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20
Q

What equations can be used to calculate the resting metabolic rate?

A

The Harris Benedict Equation
Mifflin-St Jeor Equation

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21
Q

What are the pros/cons of equations used to calculate resting metabolic rate?

A

Pro - adjustable to sex, age, height and weight
Cons - reflext population at the time, different diets and levels of physical activity, influence the assumptions of what makes up resting metabolic rate.

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22
Q

Describe how resting metabolic rate can be calculated from oxygen consumption in the lab.

A

Used a patient in the relaxed supine position
Measure VO2 expired over five minutes extrapolate to 24 hours. Calculate the RER value to look up the energy value per litre of oxygen from a reference table, multiplied by the volume of oxygen consumption.

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23
Q

Suggest why lab-measured RMR may be higher than predicted values

A

Person not fully rested - may have worrying thoughts, may be distracted,
Temperature - may be cold
May have subtle movements - as awake status

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24
Q

What are the scaling factors used to adjust resting energy expenditure to physical activity?

A

Sedentary x1.2
Lightly active x1.375
Moderatly active x1.55
Active x1.725
Very active x1.9

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25
Q

Why does exercise increase metabolic rate?

A

Skeletal muscle is a highly metabolic tissue
During exercise additional muscle fibres are recruited, and metabolic activity increases in proportion with intensity.

26
Q

Why does the metabolic rate decrease when we sleep?

A

Decreased activity of skeletal muscle

27
Q

What clinical factors can increase resting metabolic rate?

A

Burns
Hyperventilation
Hyperthermia
Hyperthyroidism
inflammation
Metabolic acidosis
Morbid obestiy
Overfeeding
Physical agitation
Sepsis
Stress

28
Q

What clinical factors will decrease basal metabolic rate?

A

Coma/deep sleep
General anesthesia
Heavy sedation
Hypothyroidism
Gluconeogenesis
Metabolic alkalosis
Paralysis
Sarcopenia/cachexia
Starvation/underfeeding.

29
Q

What tissues consume the most energy at rest v at exercise?

A

Rest - liver and brain
Exercise - skeletal muscle, heart and skin

30
Q

Why might a patient be asked to exercise in a clinical setting?

A

Understanding of how well the cardiovascular, ventilatory and skeletal muscles work together
Combine with cardiopulmonary testing.
Aims to explain presenting symptoms such as fatigue, breathlessness, chest pain or leg pain etc.

31
Q

What is the purpose of CPET?

A

Identify what factors influence exercise intolerance
Identify the function of the heart and lungs

32
Q

What are other terms for exercise tolerance?

A

Peak oxygen consumption
Maximum oxygen consumption
Functional capacity

33
Q

What factor influence exercise tolerance?

A

Capillary density
Oxidative enzymes
HR and SV - influence cardiac output
Hb% saturation rates
All influence VO2 max

34
Q

What is measured in a CPET?

A
  1. Mask that will analyse the volume and proportion of expired air (O2 and CO2), measure rate of flow (spirometer) - used to calculate oxygen consumption and volume of CO2 produced.
    2.Blood pressure cuff is attached to upper arm
    3.12 Lead ECG
    4, Pulse oximeter
  2. In some scenarios blood gases may also be taken
  3. Calculate work rate**
  4. Symptomatic reports
35
Q

What tests may be done in preparation for a CPET test?

A

Lung function
To identify FEV and Vital Capacity
Allows to estimate maximal voluntary expiration - indicates ventilatory capacity.

Estimate maximum heart rate.

36
Q

What happens in the CPET test?

A

The patient sits on a cycle ergometer
Cycles at a steady but moderately active rate for 10-12 minutes

37
Q

What values can be derived from a CPET?

A

Respiratory exchange rate
The anaerobic threshold
Heart rate recovery
Breathing reserve - the difference between maximum voluntary ventilation and maximum exercise ventilation.
Work efficiency slope - O2 consumption divided by the workload.

38
Q

Under what criteria must a CPET test be stopped?

A

ST depression or elevation
Significant arrhythmias causing symptoms or haemodynamic compromise
Rapid fall in systolic blood pressure
Hypertension
Severe desaturation
Loss of coordination
Mental confucsion
Dizziness or faintness

39
Q

What are some contraindications for a CPET?

A

Absolute: syncope, MI, unstable angina, uncontrolled asthma, endocarditis, uncontrolled arrhythmia etc

Relative: hypertrophic cardiomyopathy, abdominal aortic aneurysm,. electrolyte abnormalities, advanced or complicated pregnancy, arrhythmias, coronary stenosis or aortic stenosis.

40
Q

What different protocols may be used in CPET testing?

A
  1. Graded ‘step’ protocol - work increases at regularly over time allowing to reach steady state
  2. Constant load protocol - constant workload, exercise continuously.
  3. Ramp protocol - increments are very small and made regulary.
  4. 6 minute walk test - aim to complete as many laps between cones of set distance as possible
  5. Incremental shuttle walk test (bleep test) and record distance walked (set point between cones)
41
Q

What toole is preferred for a CPET? What else may be used?

A

Cycle test is most commonly used
Treadmill test (where speed and gradient may be changed)

42
Q

Why are the chosen intervals in a CPET test important?

A

Too small - patient reaches maximum effort and fatigue very quickly, too fast to observe the necessary changes in symptoms.

Too large - takes too long for the patient to reach VO2 max, loose motivation as test prolonged or become fatigued. Unneccessary.

Aim to complete test within an 8-10minute ratio.

43
Q

How do you determine what a good interval in a CPET test would be?

A

Based on normal level of fitness (athletes require higher intervals)
Ask about symptomatic appearance and limitation
Determine what is safe for a person of their health
Use validated work load algorithms** (specific in lecture not in notes).

44
Q

What are the benefits and cons of using a cycle in CPET tests?

A

VO2 max of patient tends to be lower
Can calculate work rate measurement
Easier to collect blood gas
Less noise and artifacts
Less weight bearing patient (hold more of patient weight) (so lower metabolic response)
Safer, cheaper and easier to store
Require less patient familiarisation
Can cause leg muscle fatigue before symptomatic end point in those not cycling
Is most suitable for patients

45
Q

What are the pros/cons of using a treadmill in a CPET test?

A

Gives a higher value of VO2 max
Can not measure work rate and is more difficult to get blood gas collection
More noise and artefacts
Less safe
More weight bearing for patient (holds less of patient weight)
Requires more leg muscle training
Most appropriate for active normal subjects.
Require more space (for crash mat), more expensive and harder to store.
Patients often more familiar with walking.
Utilises all of the body mass, provides greatest physical stress.

46
Q

How does O2 consumption change with workload?

A

Lower levels of exercise - oxygen consumption increases with work rate - relatively proportional - does so in a way to ensure only supplying enough oxygen to meet the needs of recruited skeletal muscle.

Higher levels of exercise - plateau of oxygen consumption - reached maximal oxygen consumption - also known as ventilation threshold.

47
Q

How does CO2 produced vary during incremental exercise?

A

At lower work load - nice linear increase
At higher work load - continues to increase but at a higher rate (no longer linear), indicates more CO2 produced than O2 consumptions - indicates anaerobic respiration

48
Q

Why is additional CO2 produced at higher rates of exercise workload?/

A

Aerobic metabolism - produced CO2 in proportion to O2 consumption

Also anaerobic metabolism - increased pyruvate conversion to lactic acid, which is buffered for in the blood by bicarbonate ions, which dissociate into H+ and CO2 resulting in increased production of CO2.

49
Q

What should the change in Respiratory Exchange Ratio be in exercise?

A

Typically increases in a linear fashion - due to increased reliance on carbohydrates over fats during exercise
Within the start of exercise may decrease slightly (elevated before exercise due to anxiety due to test)

50
Q

Suggest what changes are responsible for helping to increase metabolic rate during moderate and sustained exercise.

A
  • recruitment of more skeletal muscle fibres that have a very high metabolic rate.
  • increase in heart rate and stroke volume - increase CO - more oxygen/blood transporter to muscles, greater supply to cells to increase cellular respiration
  • increase respiratory rate and higher tidal volume due to changes in blood CO2 and O2 detected by chemoreceptors
  • adrenaline, may start a stress response
51
Q

What is the cardiovascular drift in exercise?

A

Originally in exercise blood flow is directed to the skeletal muscles to reach increased activity hence metabolic demand
Early in exercise - rise in body temperature causes some blood flow to be directed to the skin - this aids in cooling down the body but can temporarily reduce oxygen supply to the skeletal muscles

52
Q

Suggest what changes you expect to see in short high intensity exercise?

A

Periods of rapid recovery interweaved by physiological responses to exercise.
After a period of time will start to fatigue - leads to increased physiological response - higher HR and RR - some blood will also be diverted to the skin to aid cooling.

53
Q

How does RQ value vary between exercise and at rest?

A

Increases from rest to exercise linearly
At rest more metabolism of fats at exercise more carbohydrate metabolism
Will eventually increase above 1 to 1.5 or 2, due to the appearance of anaerobic metabolism and buffering of lactic acid leading to more CO2 production.

54
Q

Patients suffering with diabetes mellitus may have a low RQ value, can you suggest why?

A

Dysfunctional carbohydrate metabolsim (due to lower or resitance to insulin)
More reliant on fat metabolism
Which is indicated by lower RQ values (0.7)

55
Q

How does blood pressure tend to relate to the volume of blood?

A

2ml of blood entering the arteries would increase blood pressure by 1mmHg

56
Q

How does blood pressure relate to stroke volume?

A

Pulse pressure - systolic - dystolic pressure
Pulse pressure x2 = stroke volume

57
Q

How do you calculate cardiac output?

A

CO L/min = SV (ml/100mL/L) x heart Rate (bpm)

58
Q

How do you calculate pulse pressure?

A

Systolic blood pressure - diastolic pressure

59
Q

How does stroke volume change during exercise?

A

Increase linear
Then plateaus - after this, the only way to increase cardiac output is to increase HR

60
Q

What is the difference in response to exercise on a bike compared to a treadmill?

A

Bike - lower response (due to less weight-bearing, leg fatigue, smaller increase in VO2 max)

Unit 10 (37 decks)

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