Cardiorespiratory Fitness Testing

Definitions

Cardiorespiratory Endurance

  • Definition: The ability to perform dynamic exercise involving large muscle groups at moderate to high intensity for prolonged periods.

Maximum Oxygen Uptake (VO2max)

  • Definition:

    • Rate of oxygen uptake during maximal exercise.

    • Maximum amount of O2 the body can utilize at max exercise.

    • The “gold standard” measure of Cardiorespiratory Fitness (CRF).

    • Note: Exercise fitness evaluation should always include an assessment of cardiorespiratory function.

Absolute Oxygen Consumption

  • Definition: Measured in liters per minute (L/min).

    • Directly related to body size.

Relative Oxygen Consumption

  • Definition: Measured in milliliters per kilogram per minute (mL/kg/min).

    • Used to compare CRF independent of body size.

Converting Absolute to Relative Oxygen Consumption

  • Method for normalization to body size.

Importance of Aerobic Capacity

  • Aerobic capacity (CRF) is a more powerful predictor of mortality than any other risk factor in both normal and cardiovascular disease (CVD) patients.

  • Each 1 MET increase corresponds to a 12% improvement in survival.

  • Maximal Aerobic Capacity (VO2max) expressed in METS (Metabolic Equivalent of Task).

Purpose of Testing

  • Identify Fitness Status: Assess fitness status and risks for CVD and mortality.

  • Screening for CVD: Resting EKG may not tell the whole story; evaluation during strenuous activity is sometimes necessary.

  • Exercise Programs: Results used to prescribe exercise programs (i.e., %VO2max) and evaluate their effectiveness based on observed changes.

  • Motivation: Help alert or motivate individuals regarding the need to improve their fitness levels.

Resting Assessments

  • Historically, CRF was evaluated by resting measurements, including:

    • Heart Rate

    • Blood Pressure

    • EKG/ECG

  • Caveat: These measurements are not very good indicators of CRF; they are mainly used to screen for problems and assess CVD risk. Generally fit individuals tend to have lower resting heart rates. CRF must be evaluated based on oxygen uptake responses during exertion.

Measuring Aerobic Capacity

  • Open-Circuit Spirometry: A measure of gas exchange during graded exercise tests (GXT).

    • Gradual increase from sub-maximal to maximal effort.

  • Regression Equations: Applied to the results of testing protocols, either maximal or submaximal.

Common CRF Tests

  • Field Tests: Includes walking or running tests (submaximal or maximal).

  • Treadmill: Can be submaximal or maximal testing.

  • Cycle or Rowing Ergometer: Also used for submaximal or maximal testing.

  • Step Testing: All are classified as graded exercise tests (GXTs).

Graded Exercise Tests (GXTs)

  • Definition: A multi-stage exercise test where exercise intensity progressively increases, bringing the subject to a self-imposed fatigue level.

  • Common GXT Types:

    • Step tests

    • Cycle ergometer

    • Both maximal and submaximal tests must measure workload effectively.

Key Submaximal Testing Assumptions

  1. A steady-state heart rate (HR) is obtained for each exercise work rate.

  2. A maximal HR for a given age can be estimated as 220 minus age (220-age).

  3. Mechanical efficiency remains constant across individuals at a given work rate.

  • Implication: This may not hold true, suggesting that submaximal testing could underestimate VO2max in untrained individuals and overestimate it in trained subjects.

  1. A linear relationship exists between HR and VO2max between 110-150 bpm.

  2. HR variability correlates with fitness levels among subjects for any given workload.

  • Note: The above assumptions can lead to errors; hence, submaximal GXTs may not be as accurate as maximal GXTs.

Heart Rate and Intensity Assumptions

  • Graphical Representation: Relationship illustrated between heart rate (beats/min) vs. treadmill speed (km/h) for various fitness levels, emphasizing the HRmax (maximum heart rate).

HR vs. Workload Assumption

  • Another graphical representation detailing the workload (kgm/min) associated with different heart rates for untrained vs. trained individuals.

Field Test Examples

  • Sherman C. Amith: Example of a subject undergoing field tests to evaluate CRF.