5: CRF Flashcards
Cardiorespiratory Fitness
– Maximal aerobic capacity
– Functional capacity/Physical work capacity
– Cardiovascular endurance, fitness or capacity
– Cardiorespiratory endurance, fitness or capacity
Cardiorespiratory Fitness
- One’s ability to aerobically perform dynamic exercise utilising large
muscle groups (maximal ability = max aerobic/CR capacity) - Ability to perform dynamic, moderate to high intensity exercise
involving large-muscle groups for prolonged periods (CR endurance). - Reflects the functional capabilities of the heart, blood vessels, lungs
and skeletal muscles to perform work. - One of the best indicators of the health and function of the body
Reasons for assessing
Cardiorespiratory Fitness
- Inform people about their current CRF status relative to
standards and age & sex matched norms - Tailor goals/training programme to current CRF levels -
motivational - Periodically assessing CRF allows progress to be tracked
– motivational - Determine risk of developing cardiovascular disease
(client education & developing appropriate exercise
prescriptions to reduce their CVD risk)
Why is CRF important for health?
1) Relates to functional status/capacity (ability
to perform common everyday activities)
2) Low CRF is an independent risk factor for
all-cause and cardiovascular (CV) mortality.
Risk Factors for CVD
- Positive risk factors:
– Age
– Family history
– Cigarette smoking
– Sedentary lifestyle
– Obesity
– Hypertension
– Dyslipidemia
– Prediabetes
– Low CRF - Negative risk factor:
– High serum HDL
cholesterol
- Low CR fitness increases the risk of:
– premature death from all causes (regardless of weight status)
– Premature death from CVD (regardless of weight status)
– developing CVD, Type 2 diabetes, some cancers
Improving CRF (regardless of weight status) can reduce the risk of
all-cause and CVD death
- High CR fitness is related to:
– higher levels of habitual PA
– higher PA levels are associated with many health benefits
– Higher functional status (ability to perform common
everyday activities without tiring)
Pretest Standardizations for CRF
Assessments,
* Participants should be instructed to:
– Wear appropriate clothing
– Avoid tobacco & caffeine 3 hours prior to test
– Avoid alcohol 12 hours prior to test
– Obtain adequate sleep night before test
– Keep hydrated
– Avoid strenuous exercise for 24 hours before the test
Gold standard measure of CRF
- Maximal exercise test with collection of
expired gases to determine VO2max - Performed in the Lab setting
- Primary outcome is directly measured
VO2max - Participant cycles or runs until complete
exhaustion
Selecting the Mode for Max Testing:
Common modes
- Treadmill—the default mode for most facilities due to its
similarity to daily activities and typically the highest VO2max - Cycle ergometer—non weight bearing exercise, good for obese or
disabled individuals, trained cyclists, lower values for VO2max why? - Test stopped at maximal capacity (indicators?) or if subject
experiences any absolute or relative indications (see box 8.1. of
ACSM textbook) - Need to use a standard protocol for treadmill or cycle ergometer
– Accurate and reliable measure of CRF
– Interpret CRF results by comparing to normative data
Measured and Estimated VO2max
- Gold standard tests will directly measure VO2max with a
metabolic measurement system - If metabolic system not available
– VO2max can be estimated (based on exercise test time or workload achieved) using equations
and/or
normative data (as long as a standard protocol has been used)
If maximal exercise testing with collection of expired gases is the gold standard:
Why can we not always perform this test?
- Lack of…
– Facilities
– Equipment
– Personnel
– Time - Risk associated maximal exercise testing
- Alternatives to estimate CRF are:
– Field tests
- Takes place in a variety of non laboratory settings, typically by a group people, max/near max tests and submax tests (level of effort limited to submaximal exertion)
Field tests of CRF
– 1-mile walk test
– 1.5-mile run test
– 12 minute run test
– 3 minute step test
– 20 metre shuttle run test/bleep test
Step Tests
- Fixed amount of work in a set amount of time (submax test)
- Subjects step up and down on a step height (16.25in) for 3
minutes at a set rate (different step rates for men & women) - Immediately after completion, heart rate (HR) is measured
and used to estimate VO2max
1 Mile walk test
- Subject asked to walk 1 mile around a measured course
as quickly as possible
– 1 foot in contact with ground at all times
1.5 Mile run test
- Subject asked to run 1.5 miles around a measured course as
quickly as possible - VO2max(ml.kg.min-1) = 3.5 + 483/1.5 mile time (mins)
- 12 minute walk/run test
- Subject covers maximum distance (expressed in meters)
in 12 minutes - VO2max(ml.kg.min-1) = (distance in meters – 504.9)/44.73
Multistage Fitness Test (Bleep Test)
- Maximal exercise test
- Use the level and shuttle achieved to estimate VO2max using published equations or tables
– e.g. see the bleep test score calculator on Topend Sports - Use the level and shuttle achieved and compare it to normative data (age and sex) to categorise fitness level
weakness of field tests to measure CRF
- Majority of field tests have been developed for use with younger, low risk individuals
- Many of these tests would not be suitable for individuals with moderate or high risk of CVD
- Estimating VO2max using prediction equations, measurement error
Strengths of field tests to measure CRF
- Minimal equipment
- Low cost
- Personnel
- Time efficient
- Generally safe (for young, low risk groups)
Factors influencing the accuracy &
reliability (consistency) of the measurement of CRF from field tests
- Subject not following pre-test instructions
- Tester not following standardised procedures
- Learning effect, not practising the test
– 1.5 mile run test & 12 min walk/run test - Subject motivation
– bleep test, 1.5 mile run test & 12 min walk/run test - Estimating VO2max using prediction equations introduces measurement error
- If the characteristics of the subject do not match the characteristic of the population used to develop the equation or the norms table then VO2max might be overestimated/underestimated
