Exam 1 Flashcards
Relationship between glycogen stores and fatigue
slow ATP production and increased cellular acidosis which promotes fatigue
What does beta-oxidation produce?
H+ for electron transport chain and acetyl-CoA for Kreb’s cycle
At rest, what is providing 50-90% of energy?
lipids
what is alanine important source of?
gluconeogenesis in the liver during long term endurance exercises
how is the rapid synthesis of ATP accomplished during the first 6-8 seconds of exercise?
hydrolysis of creatinine phosphate
How long should a glycolysis exercise test be?
longer than 6-10 seconds but shorter than 3 minutes
what does peak power output assume?
CP-ATPase capacity is tested
what does average power output assume?
glycolytic capacity is tested
what does the O2 deficit during the transitional stage represent?
the energy that was provided by anaerobic metabolism
during submaximal exercise, where is the majority of energy derived from?
aerobic processes
at a steady state in sub maximal exercise, what is there a balance between?
energy demand (energy expenditure in kcal) and oxygen uptake (L/min) which is why VO2 is a good index of energy expenditure
Health related components of physical fitness
cardiorespiratory endurance or fitness, body composition, muscular strength and endurance, flexibility
what is Vo2max?
the maximal capacity to transport and utilize oxygen (capacity for aerobic transfer)
Cardiorespiratory endurance/fitness
ability to perform large muscle, dynamic, moderate to high intensity exercise for prolonged periods
what is low level cardiorespiratory fitness associated with?
markedly increased risk of premature mortality from all causes, especially cardiovascular disease
what is increased cardiorespiratory fitness associated with?
a reduction in death from all causes
higher levels of habitual physical activity, which in turn is associated with health benefits
purposes of cardiorespiratory fitness testing
- obtain data needed for writing exercise prescriptions
- evaluation of progress in an exercise program
- motivation via provision of realistic exercise goals
- education on current fitness status
- health related risk stratification
What type of subjects are typically tested in health-related cardiorespiratory fitness testing?
asymptomatic adults
purposes of clinical exercise testing
- diagnostic testing
- testing for disease severity and prognosis
- clinical management
- pre and post discharge testing
- functional testing
Common ECG finding with myocardial ischemia
ST segment depression or elevation
purpose of ECG monitoring
- assess presence and severity of CAD
- predict likelihood of future cardiac events
- analysis of exercise induced arrhythmias
What is radionuclide exercise testing and why is it important?
radionuclides are rapidly taken up by cardiac muscle
the pattern and rate of uptake and clearance provides information on myocardial perfusion and ventricular function
what can assessing myocardial profusion detect?
coronary artery stenosis and muscle ischemia
what is radionuclide exercise testing clinically used for?
diagnosis of CAD in symptomatic individuals
prognosis of future event in patients with stable CAD
post MI assessment of myocardia ischemia, viability and ventricular function
What does stress echocardiography give information on?
- myocardial contractility
- cardiac volumes (ejection fraction)
- valvular function
what is the major use of stress echo and radionuclide imaging?
detect ischemic coronary artery disease
what is the gold standard for determining aerobic capacity?
directly measuring VO2 max
disadvantages of directly measuring VO2 max
- costly equipment
- specially-trained personnel
- time-consuming
- requires subjects to exercise to volitional fatigue
what is the second most accurate way of evaluating/determining aerobic capacity?
estimating VO2 max from maximal exercise testing (often used in clinical SLM-GXT)
how do you estimate VO2 max from a submaximal testing protocol?
- determine HR-VO2 relationship during progressive submax exercise or determine HR-exercise intensity relationship during submax exercise
- predict VO2max from the relationship determined using prediction equations
Primary criteria for reaching VO2 max
plateau in oxygen uptake with a further increase in workload
secondary criteria for reaching VO2max
- fatigue
- respiratory exchange ratio greater than or equal to 1.10
- HR during last stage that is within 10 beats per minute of age predicted max HR
- future of HR to increase with an increase in intensity
- RPE greater than 17 (on 6-20 scale) or greater than 9 (on 0-10 scale)
- post exercise venous lactate > 8 mM
what can influence RPE?
mood state, environmental conditions, exercise modes, and age
what factors can affect VO2 max?
- mode of exercise
- genetics
- gender
- body size and composition
- obesity
- aging
- activity level/training
what mode of exercise testing usually results in the greatest VO2 max value?
treadmill test
what factors contribute to the gender differences in VO2 max?
body composition, Hb concentration, variations in physical activity
what is VO2 max proportional to?
amount of contracting muscle
what do variations in body mass explain?
nearly 70% of the differences in VO2 max and accounts for most of the gender differences in VO2 max
how does age affect VO2 max?
VO2 max rises during childhood and peaks around age 20-25
decreases with age (about 1% per year after 25yo)
What is glucose converted to?
pyruvate then to either lactate or acetyl-CoA
What is EPOC?
difference between VO2 measured after exercise and the actual resting VO2 measured prior to exercise
Should be equal to the O2 deficit present before reaching steady state
Fast component of EPOC
- resynthesizes CP and ATP stores in muscle
- replaces oxygen stores in blood, body fluids, and myoglobin
slow component of EPOC
- lactate removal
- elevated core temp
- elevated hormones
- O2 demands of heart, respiratory muscles, etc during recovery
Purpose of submaximal exercise testing
prediction of VO2 max (max aerobic capacity) from an endpoint measured during a submaximal exercise effort
Types of endpoints in submaximal exercise testing
HR during steady-state exercise or immediately after exercise
time to complete a given submaximal workload
Submaximal testing advantages vs maximal testing
- easier, faster to administer to large groups of persons
- less expensive equipment and less specialized training are required (if VO2 is not measured)
- subject motivation is less of a concern
- decreased probability of provoking a cardiac event during exercise
typical measurements during submaximal testing
- heart rate
- blood pressure (not practical during field tests)
- RPE
- for field tests: time to complete a standard workload or distance covered in a standard period of time
- signs and symptoms of cardiac or pulmonary distress
why do we use heart rate to predict oxygen consumption?
- there is a strong positive relationship between cardiac output and VO2 during aerobic exercise
- the rise in heart rate is primarily responsible for the increase cardiac output during exercise (peak rise in SV occurs at light intensity)
- there is a close relationship between HR and VO2 when intensity is increased from high to moderately heavy workloads
Explain cardiac output and its relationship to VO2
CO is proportional to VO2
CO = HR x SV
CO is linearly related to heart rate during moderate exercise
Therefore, VO2 is linearly related to heart rate response during moderate exercise
what is the goal of measuring steady-state HR to predict VO2max in cycle ergometry?
measure steady-state HR at 2 or more consecutive workloads considered light to moderately heavy for the subject
how long are the stages (workloads) when using steady-state HR to predict VO2max in cycle ergometry?
about 3 mins
must be in steady state (2 HR measurements within 5 bpm) before workload is increased again
When using steady-state HR to predict VO2max in cycle ergometry, how many consecutive stages do you need?
2 or more that elicit HR between 110 and no more than 85% of predicted max HR (or 70% or HRR) in order to predict maximal workload or VO2
What are the assumptions underlying the prediction of aerobic capacity from submaximal HR?
- steady-state conditions are present when measuring HR
- duration of stages are usually >90 secs to 3 mins
- a linear relationship exists between HR and VO2 up to maximum exercise
- maximal HR at a given age is uniform among individuals
- mechanical efficiency or oxygen cost of the activity is the same for all individuals
can ramp protocols be used when predicting aerobic capacity from submaximal HR?
no
where does the tightest linear relationship between HR and VO2 occur?
when the workload is <85% (moderately heavy) of predicted heart rate
is maximum HR at a given age actually uniform?
no, it varies +/- 10-12 bpm from predicted value
this is an unavoidable source of error
does poor economic result in an over or underestimation of aerobic capacity?
underestimation
what effect does handrail support have on O2 cost?
reduces it by 30%
how much should you expect walking/cycling and stepping economy to vary among individuals?
walking/cycling: +/- 6%
stepping: +/- 10%
What other factors can affect the slop of the submaximal HR:VO2 relationship?
- dehydration or exposure to heat/humidity
- eating prior to the test
- alcohol, caffeine
- fear, excitement or other emotional stress (less important at higher workloads)
what accuracy can we expect when predicting VO2max from submaximal HR?
- generally, VO2 max predicted from submaximal HR is within 10-20% of the individuals actual value
- this is suitable error for general screening and categorizing “fitness” levels
- submax tests are also an excellent method for following a subject’s progress though a training program
on average, how much did the submax test (using predicted HRmax) under predict VO2max?
250 ml/min
Modes of Submaximal Exercise Testing
- many are based on cycle ergometry
- others include treadmill and bench-stepping
- field tests (depending on subject motivation and pacing ability)
what is bench stepping tests good for?
mass testing because it utilizes easy and cheap equipment
Single-Stage Submaximal Treadmill Test
- a 2-4 min walking warm up at 2-4.5 mph with 0% grade
- patient walks for 4 mins at 5% grade at walking pace (2-4.5 mph)
- measure HR at end of 4th minute (steady-state)
- use prediction equation (speed, HR, age, gender)
how accurate is the single-stage submaximal treadmill test?
+/- 5 ml/kg/min
Submaximal Step tests categories
- use the exercise HR just prior to the end of the exercise bout –> the lower the HR, the greater the aerobic capacity
- use the recovery HR determined during a specific period post exercise (# of bpm in one minutes starting 5 seconds into recovery) –> the faster the recovery/the lower the HR, the greater the aerobic capacity
Rockport One-Mile Walking Test
- walk as fast as possible a one-mile course on level terrain or track
- count HR for 15 seconds immediately post exercise (x4bpm) or use HR monitor
Cooper 12 minute test (field test)
- objective is to cover the most distance possible in 12 mins (can walk or run)
- published normed by age and gender
1.5 mile run test (field test)
objective is to cover 1.5 miles as fast as possible
Non-exercise estimate of VO2max
estimates VO2max from age, physical satiety status, and body composition
accurate in subjects with VO2max <55 ml/kg/min
non-exercise estimate of VO2max derived from FRIENDS Registry
uses age, sex, and body weight (in lbs)
<5 METs
<17.5 ml/kg/min
Poor prognosis
usual limit of functional capacity immediately after MI
peak cost of basic ADLs
10 METs
35 ml/kg/min
Typical healthy 50-60 year old man
prognosis with medical therapy as good as coronary bypass surgery
13 METs
45.5 ml/kg/min
excellent prognosis regardless of other exercise responses
18 METs
63 ml/kg/min
elite endurance athletes
20 METs
70 ml/kg/min
world-class athletes
What is the 6 minute walk test and what is the outcome measured?
a clinical field test that measures the distance in meters walked by a patient in 6 minutes
when is the 6MWT used?
It is targeted at patients with at least moderately severe impairment, usually primary cardiac or pulmonary disease
Widely used for pre and post operative evaluation
what can the 6MWT predict?
morbidity and mortality in heart failure and COPD
what does the 6MWT NOT do?
directly determine peak oxygen uptake, diagnose causes of exertion dyspnea or provide insight into mechanisms of exercise intolerance
physiologic definition of maximal oxygen consumption
maximal capacity to transport and utilize oxygen
operational definition of maximal oxygen consumption
the VO2 at which oxygen uptake no longer increases with increased workload
what term is used when it is not clear that the exercise bout elicited the “true” physiologic VO2 max or when a plateau was not demonstrated?
peak aerobic power or peak oxygen uptake
Components of oxygen transport system?
- pulmonary ventilation
- transfer oxygen to the blood
- cardiac function
- blood flow to active muscle
- transfer of oxygen to the muscle
- metabolic function of the muscle
relative workload
the workload is expressed relative (%) to a standard, usually that persons maximum HR or VO2max
absoute workload
expressed at l/min or ml/min/kg of O2 uptake or as watts, mph, kgm-min, etc
what is VO2 reserve?
the difference between VO2max and resting VO2
equation for work
work = force x distance
total distance traveled on cycle ergometer
total distance traveled = revolutions/time x distance/revolution x time
what is power?
work done per unit time
direct calorimetry
measured heat liberated as a measure of metabolic rate
indirect calorimetry
measures O2 consumption as an index of metabolic rate under steady state conditions
respiratory quotient
co2 produced/o2 consumed at a cellular later due to combustion of foodstuffs
RQs of carbs, fats, and proteins
carbs: 1.00
lipids: 0.70
protein: 0.82
what occurs when RQ decreases over prolonged steady state exercise?
increased oxidation of lipids
respiratory exchange ratio
term used when CO2/O2 ratio at lungs does not accurately reflect cellular metabolism
occurs during a non-steady state exercise (start and at strenuous activity)
when does RER exceed 1.00?
during exhaustive exercise when the lactic acid is buffered by bicarb leading to increased co2 production
Resting metabolic rate
60-75% of TDDE
basal metabolic rate
the minimum level of energy required to sustain vital functions in the waking state
measured under stringent lab conditions
is BMR or RMR higher?
RMR
what strongly influences RMR?
body composition
more free fat mass = higher RMR
how does RMR change with age?
decreases
2-3% loss per decade
associated with decreased FFM
Thermic effect of food
ingestion of food increases metabolism
it is the energy required for digestion, absorption, assimilating nutrients
equivalent to 10-35% of ingested calories
large genetic component
NEAT
the energy expenditure associated with daily activity, such as posture, spontaneous ambulation, and talking
1 MET =
3.5 ml/kg/min
what can effect economy?
skill in performing activity
terrain or surface
gait mechanics or use of assistive device
when does running become more economical than walking?
about 8 km/h or 5 mph
