CARDIAC OUTPUT:
SUPINE vs UPRIGHT EXERCISE
Fall  2000
95 Points

     Cardiac output (Q; the volume of blood pumped by the left ventricle per minute) is the product of heart rate (frequency of heart beats) and stroke volume (volume of blood pumped by either the right or left ventricle each beat).   Cardiac output has a direct relationship to the intensity of dynamic exercise.   Heart rate and stroke volume interact to maintain the required cardiac output.

     Cardiac output is often evaluated in the clinical setting using exercise testing more advanced than simple treadmill stress tests.   In the clinical setting, cardiac output is more easily measured in the supine position. However, exercise prescriptions are given for the upright position.

    The purpose of this lab is

  • to determine the nature of the relationship between cardiac output and oxygen consumption (VO2)
  • to compare the cardiac output-VO2 relationships between supine, recumbent, and upright exercise
  • to apply the HR-VO2 relationships to the supine and upright exericse scenarios
  • to determine the influence of posture on energy expenditure

Click here to download the lab write-up.

Click here to download the data form.
Turn this data form in to Dr. Wallace as soon as you collect the data.

 

LABORATORY PROCEDURES

  1. Prepare the subject for the measurement of


    2.
    1. heart rate
    2. expired gases using the Sensor Medics 2900 Metabolic Cart
    3. blood pressure measurement
    4. cardiac output using the Sensor Medics 2900 Metabolic Cart or bioelectric cardiac impedence
  2. Use the Pause feature on the metabolic cart for the periods between rest and exercise.


  3. Use a subject who has had previous determination of VO2 max.   From the previous data determine a target VO2 for 20% and 50% of VO2 max.    Use the table below for calculations
    4.

            ml/min kg                 L/min                 ml/min        
    VO2 max               
    20% VO2 max               
    50% VO2 max               


  4. Determine approximate workrates on a cycle ergometer for 20% and 50% of VO2 max, using the following formula:

    Target VO2 (ml/min) = [(Kgm/min) x (2 ml/kgm)] + [(3.5 ml/min kg) x (wt kg)]


    The workrate (kpm/min) is the unknown in the above formula.   Use the table below for calculations:

    5.         ml/min                  Workrate (kpm/min)                 Load (kg)                 RPM        
    @ 20% VO2 max                    
    @ 50% VO2 max                    

  5. Measure heart rate, blood pressure, oxygen uptake, and cardiac output at rest, in the
    1. Upright
    2. Recumbent
    3. Supine position

    for 5 minutes.   Randomize the order of the three positions for the different lab groups.  Do not randomize the rest and exercise intensities within the position.

    6. Supine Rest
    Upright Rest

  6. Have subject exercise at 20% in the same position measured in #5 above.   Each workrate should be done for at least 5 minute.   Measure the cardiac output after the subject has reached steady state; perhaps the last two to three minutes.

  7. Have subject exercise at 50% in the same position measured in #5 above.   Each workrate should be done for at least 5 minutes. Measure the cardiac output after the subject has reached steady state; perhaps the last two to three minutes.

    8. Supine Exercise
    Upright Exercise

  8. Repeat procedures 5, 6, & 7 again with the subject in one of the other positions.

  9. Repeat procedures 5, 6, & 7 again with the subject in one of the other positions.

Click here for a recording form.

References:

  1. Exercise Physiology Textbooks
  2. Astrand may be a good reference.
  3. McArdle, Katch and Katch, Exercise Physiology: Energy, Nutrition and Human Performance, may be the best reference.
  4. ACSM Resource Manual

QUESTIONS

Indicate references, including page numbers.

  1. Plot the cardiac output response to supine, recumbent, and upright exercise (5 points).

  2. Plot the stroke volume response to supine, recumbent, and upright exercise (5 points).

  3. Plot the heart rate response to supine, recumbent, and upright exercise (5 points).

  4. Describe the differences and similarities in cardiac output among positions, for the the 20% workrate.    (10 points)

  5. Describe the differences and similarities in cardiac output among positions, for the the 50% workrate.    (10 points)

  6. What variable (heart rate or stroke volume) appears to be more responsible for these differences?    What evidence supports this? (5 points)

  7. Does the relationship between cardiac output and VO2 change with position changes?   If so, how?   Explain the possible mechanisms. (10 points)

  8. What clinical exercise tests are administered in the supine or recumbent positions? (5 points)

  9. Can a valid target heart rate be given for upright or recumbent exercise from a supine stress test?   Expalin.   (10 points)

  10. Plot the energy expenditure (VO2) of supine, recumbent, and upright exericse vs the workrate(5 points).

  11. What clinical population exclusively uses recumbent cycling for training in an out-patient rehabilitation setting? (5 points)

  12. How does recumbent cycling differ from upright cycling for energy expenditure, cardiac output, and heart rate response? (10 points)

  13. How does recumbent cycling differ from supine cycling for energy expenditure, cardiac output, and heart rate response? (10 points)

  14. Can a valid target heart rate be given for recumbent exercise from a either an upright or supine stress test?   Expalin.   (10 points)
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