The user wishes to simulate an endurance exercise bout. Exercise simulation setup requires the user to change the value of more than one variable. In this case both the level of exercise (EXER) and the duration of exercise (XERMIN) must be changed.

1) To set up HUMAN for exercise and obtain control pre-exercise values, at the opening screen (see below)

Select

• Pick Experiment number 1 (see above left)
• Run for 10 minutes with 10 minutes between printouts.

Click on <Run>
- this results in the "Output from Web-Human Physiology Simulation" shown below

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Note that in this case the tables preset for experiment #1 already contain useful variables for an exercise readout (AP= arterial pressure, COL = cardiac output, etc.)

2) HUMAN is now ready to be set up to exercise for one hour with data readouts every 5 minutes. The level of exercise (EXER) will be set at 2.0 Liters/min. of O2 usage above basal and the duration of exercise (XERMIN) will be set at a sufficiently high value (120 minutes) to not terminate the exercise. The steps involved in the user control panel (see below) are

To set up exercise parameters (duration and intensity)

• Under Experimental Controls (lower left)
• Roll down Choose under Change Variable (button #1) to XERMIN and enter 120 (Enter New Value)
• Under Change Variable (button #2) roll down to EXER.
• Enter 2.0

To obtain both tabular (i.e. text) and graphic output

Under the View Output: section (top)
In the as: row (i.e. the 2nd row)
Change the output choice from text to graph for the first 5 variables (as shown below)

To begin the actual experiment at the above chosen values

• Under Run Experiment type in 1H (H =hours) with 5 (min.) intervals between printouts.
• Click on <Go>.

When the tabular and graphic outputs appear, click on the tabular output to bring it to the foreground. The tabular results of the experiment are shown below.

Some things to note:

The model exercised for about 25 minutes (after which EXER returned to zero). The model ceases exercising whenever it runs up a total O2DEBT of greater than 10L (which occurred here at 27 min.)

The cardiac output (COL) rises but less so, percentage-wise, than the ventilation (VENT).

At rest about 1/5 of the cardiac output (COL) is being sent to the muscles (MFLOL). As a result of exercise vasodilation, at its peak almost 13/17 of the cardiac output (see 12:15 AM) is directed towards the muscles.

Arterial pressure (AP) rises only slightly.

Graphing Data Outputs in web-HUMAN*

Now click on the graph window bringing it to the forground.
You obtained this 5 variable graph because, in addition to having selected graph as an output form,
in the View section (see below) you, by default, have chosen a graph style (see bottom) that was

- normalized (plots changes in the variable relative to baseline value) and
- a single plot (showing all the variables on one plot as opposed to individual plots)
*for more industrial grade plotting see the instructions in Help on How to Graph in Excel

The results of this graphing (seen below) confirm that exercise terminates at near 25 min. due to a near 10 Liter total O2DEBT and that Cardiac Output, Ventilation, etc. show a pattern closely responsive to the level of exercise.

A snapshot of the physiology of individual systems at this point in time can be obtained by rolling down the "Patient Charts or Lab tests " option (see below) under the View section and selecting the system of interest (in this case the ventilatory system).

The results of this snapshot in time for the respiratory system (here at 1 hour) follow.

Some additional possibilities

• Repeat the experiment (use the Start Over option) setting up the tables to study O2 delivery and extraction (use the List all variables option on any Help Info On: <Choose> screen). Some possibilities for variables are oxygen contents (O2A, O2V), partial pressures (PO2A, PO2V), etc.
• Try to get the model to 'run' for 24 hours (EXER = 0.75 yields a stable O2DEBT, set XERMIN > 24H). In addition to gas delivery, water balance, salt balance and body temperature rise must also be dealt with.
• Try to increase exercise endurance by supplying the respiratory system with 100% O2 (see FO2AT - the fraction of O2 in the atmosphere). Try to increase endurance by simulating cardiac conditioning. Cardiac contractility can be raised on the right and left side (see RHSB, LHSB - left heart strength basic). Which maneuver, cardiac or respiratory, yields the greater increase in endurance and why?

Note: Many of the ideas for this exercise experiment and its variations appeared originally in the Student Manual** to the microcomputer version of HUMAN written by Dr. James E. Randall, University of Indiana School of Medicine and Dr. Coleman.

**Coleman, Thomas and Randall, James E. Student Manual. HUMAN-80. Microcomputer Version of a Mathematical Model of The Human Body In Health, Disease and During Treatment, April, 1981.