Exercise for Diagnosis: Principles of Exercise Testing Flashcards
ST depression is a marker of
myocardial ischaemia
Exercise testing mainly focuses on
cardiopulmonary disease
What are reasons for exercise testing?
exercise capacity/fitness; disease risk (METs); differential diagnosis (pulmonary vs cardiac vs vascular); assessment of disease severity; pre-op risk (frailty VO2max is 18mL O2/kg/min); disability evaluation; rehab/exercise prescription (to Rx %max); effectiveness of an intervention/therapy/exercise/surgery/medication
What is the Bruce protocol?
4 stages of increasing treadmill speed and grade (10%-22%)
What are modified Bruce protocols?
increasing grade progressively (not both speed and grade) making the test longer; or smaller but more increases in grade and speed
What is a ramp protocol?
Increasing workload continuously
Ramp protocols show what with regards to O2 consumption?
continuous rise in O2 consumption measured breath by breath
What is a one minute step protocol?
increasing workload each minute, similar to ramp
What does a two-minute step protocol show with regards to O2 consumption?
shows an increase in O2 consumption then levelling off with each increase in workload
What is the benefit of starting with a step protocol then using ramp?
achieve steady states to give an idea of VO2 - PO relationship then ramp to fatigue - avoid MSK fatigue but adequately stress the CV-respiratory system
What is VO2 peak?
The highest VO2 measurable during a test
What are the criteria for VO2 max?
reaching age-predicted maximal HR; RER greater than 1.2 (significant CO2 buffering of metabolic acidosis); and VO2 does not increase by more than a few mL/kg with an increase in workload
As exercise intensity increases, lactate
increases, often exponentially
In more active groups, the lactate curve shifts
Right - ie trained muscle reaches lactate threshold later
In someone with heart disease, the lactate curve shfits
Left - ie impaired O2 delivery to the muscle causing lactic acid production
What are indirect exercise tests?
walk/run (6/12min walk) tests; beep test/20m shuttle run; using submax HR responses to predict VO2 max; VO2 - HR relationships during cycling (is HR decreased at same PO after training); harvard step test; PWC 150 and PWC 170 = physical working capacity - what PO do you need to get to HR 150 or 170 (fitter = higher PO to reach 150 or 170)
What is the limitation to extrapolating VO2 max from submaximal testing?
differences in the HR response - slope can differ between trained and untrained; max HR can change due to changes in intrinsic HR; individual differences - some increase exponentially, others hyperbolically (ie non-linearly)
VO2 max is limited by
O2 delivery; not so much mitochondrial oxidative capacity
Fuel choice is influenced by
mitochondrial capacity
Increasing mitochondria in muscle reduces reliance on which fuel?
CHO
T/F Exercise performance is purely dictated by VO2 max
False; ability to use a high proportion of VO2 max for a long period of time determines performance
What determines performance?
The ability to use a high proportion of VO2 max for long periods of time, rather than just a high VO2 max itself
Ability to exercise at high proportion of VO2 max is determined by
ability to exercise at high intensity without producing a lot of lactate (because this means you are depleting glycogen)
Muscle pyruvate oxidase assay measures
oxidative capacity
Endurance is more related to _____________ while VO2 max is more related to ______________
oxidative capacity (mitochondria); O2 carrying capacity (delivery)
Lactate threshold is more highly correlated with
muscle oxidative capacity than VO2 max
T/F Trained individuals have a high VO2 max bc they have high oxidative capacity
False; may not be causal - trained indv have more mitochondria tf a higher oxidative capacity and generally also have high VO2 max
Higher lactate threshold = ________ glycogen use
lower
Higher lactate threshold is associated with
lower glycogen use and tf longer time to fatigue; higher lactate threshold means less glycogen is used at a given exercise intensity OR for a given glycogen use you can exercise at a higher intensity
How can muscle strength be tested?
1 repetition maximums (RM); maximum voluntary contractions (MVC); can train with isometric, concentric/eccentric, isokinetic (velocity is controlled)
