Cardiorespiratory Fitness Testing
Cardiorespiratory fitness is defined by how well the body can perform dynamic activity using large muscle groups at a moderate to high intensity for extended periods.
CRF depends on the efficiency and interrelationship of the cardiovascular, respiratory, and skeletal muscle systems.
Exercise testing for cardiorespiratory fitness is useful to:
- Determine functional capacity
- Determine a level of cardiorespiratory function that serves as a starting point for developing goals for aerobic conditioning
- Identify metabolic markers (e.g., VT1 and VT2) that can be utilized to design individualized exercise programs
- Determine any underlying cardiorespiratory abnormalities that signify progressive stages of cardiovascular disease
- Periodically reassess progress following a structured fitness program
Maximal Oxygen Uptake (V02max)
Maximal oxygen uptake (VO2max) is an:
- Excellent measure of cardiorespiratory efficiency
- Estimation of the body's ability to use oxygen for energy at maximal exertion
Measuring VO2max in a laboratory involves the collection and analysis of exhaled air during maximal exercise.
- Measured in L/min = Absolute VO2max
- Divide by body weight (kg) to determine
relative VO2max (mL/kg/min)
Conducting a cardiorespiratory assessment at maximal effort is
not always feasible and can actually be harmful to certain populations.
Submaximal Cardiorespiratory Assessments
Submaximal cardiorespiratory assessments can provide relatively accurate values at a workload that can be extrapolated to determine expected O2 uptake during maximal efforts.
- As workload increases, so do heart rate and oxygen uptake.
- In fact, heart rate and oxygen uptake exhibit a fairly linear relationship to workload.
- This allows for VO2max estimates based on MHR (generally predicted).
Inaccuracies: Submaximal Cardiorespiratory Testing
Many estimation calculations are based on the calculation of 220 - age for estimating maximum heart rate (MHR).
Maximal oxygen uptake is determined by measuring HR at submaximal workloads and then extrapolating the workload and HR data to the predicted MHR to determine predicted VO2max.
A submaximal test is likely to underestimate the true maximum for an individual who is very deconditioned, and overestimate VO2max for a very fit individual.
Cardiorespiratory Fitness Assessments
- Bruce submaximal treadmill exercise test
- Balke & Ware treadmill exercise test
- Ebbeling single-stage treadmill test
Cycle ergometer tests
- YMCA bike test
- Astrand-Ryhming cycle ergometer test
Ventilatory threshold testing
- Submaximal talk test for VT1
- VT2 threshold test
- Rockport fitness walking test (1 mile)
- 1.5-mile run test
- YMCA submaximal step test (12 inches)
- McArdle step test (16 inches)
Graded Exercise Tests (GXT)
Graded exercise tests (GXT) conducted in laboratory and fitness settings typically use a treadmill, cycle ergometer, or arm ergometer to measure cardiorespiratory fitness.
- Some of the tests are administered in stages that incorporate gradual increases in exercise intensity.
- Other tests measure the heart-rate response to a single-stage bout of exercise.
- In the clinical setting, a GXT is typically performed to maximal, or near maximal, exertion.
Submaximal Graded Exercise Tests
Submaximal exercise testing is safer and, in many cases, provides a reliable indicator of maximal effort.
- The workload can be measured in metabolic equivalents (METs).
Workload is a reflection of oxygen consumption and, hence, energy use.
- 1 MET is the equivalent of oxygen consumption at rest, or approximately 3.5 mL/kg/min.
- For example: If a person is exercising at a workload of 7 METs, he or she is consuming oxygen at a rate of 24.5 mL/kg/min
(7 MET x 3.5 mL/kg/min).
- Most activities of daily living (ADL) require a functional capacity of 5 METs.
Indicators of Heart Disease Risk
A GXT is also a valuable tool in identifying those who are at risk of a coronary event.
The major indicators include:
- A decrease—or a significant increase—in blood pressure with
- An inadequate HR response to exercise
- Exercise duration (the longer the individual can tolerate the treadmill test, the less likely he or she is to die soon of CAD—or of any cause)
Monitoring the Client
It is essential to monitor the client before, during, and after any GXT.
- Heart rate
- Blood pressure
- Ratings of perceived exertion (RPE) - Signs and symptoms (S/S)
Ratings of Perceived Exertion (RPE)
(Borg 15-point Scale)
Borg 15-point Scale (RPE 6-20)
6 (corresponding HR of 60 bpm)
7 Very, Very Light
9 Very light
11 Fairly Light
12 (corresponding HR of 120 bpm)
13 Somewhat Hard
17 Very Hard
19 Very, Very Hard
20 (corresponding HR of 200 bpm)