Cardiovascular Reflexes

Posture

Exercise

Objective:

To explain in a short essay or a diagram the blood pressure, heart rate, and pO₂ that occurs during changes in posture and exercise, at the level of 85% proficiency for each student.

In order to achieve this objective, you will need to be able to:

1. Measure blood pressure, heart rate and pO₂ during sitting, reclining, standing, and exercise.

Measure differences in the cardiovascular responses of well conditioned and poorly conditioned individuals.
Explain why blood pressure, heart rate, and pO₂ change during changes in posture and during exercise.

Methods and Results

To monitor circulatory adjustments to changes in position, take blood pressure and pulse measurements under the conditions of sitting, reclining, and standing noted in Table I. Measure Arterial pressure using the the sphygmomanometer. Measure Heart rate and pO₂ using the Nonin Pulse Oximeter shown below. Record your results in Table 1.

Table 1 Posture

Sitting quietly

Reclining for 3 min

On standing

After standing for 3 min

You will be working in groups of four, duties assigned as indicated above, except that student 4, in addition to recording the data, will act as the timer and call the cadence.

Any student with a known heart problem should refuse to participate as the subject.

All four students may participate as the subject in turn, if desired, but the bench stepping is to be performed at least twice in each group--once with a well-conditioned person acting as the subject, and once with a poorly conditioned subject.

Bench stepping is the following series of movements repeated sequentially:

Place one foot on the step.
Step up with the other foot so that both feet are on the platform. Straighten the legs and the back.
Step down with one foot.
Bring the other foot down.

The pace for the stepping will be set by the "timer" (student 4), who will repeat "Up-2-3-4, up-2-3-4" at such a pace that each "up-2-3-4" sequence takes 2 sec (i.e., 30 cycles/min).

Student 4 should obtain the step (20-in. height for male subject, or 16 in. for a female subject) while baseline measurements are being obtained on the subject.
Once the baseline pulse and blood pressure measurements have been recorded on Chart 2, the subject is to stand quietly at attention for 2 min to allow his or her blood pressure to stabilize before beginning to step.
The subject is to perform the bench stepping for as long as possible, up to a maximum of 5 min, according to the cadence called by the timer. The subject is to be watched for and warned against crouching (posture must remain erect). If he or she is unable to keep the pace for a span of 15 sec, the test is to be terminated.
When the subject is stopped by the pacer, stops voluntarily because he or she is unable to continue, or has completed 5 min of bench stepping, he or she is to sit down. The duration of exercise (in seconds) is to be recorded, and the blood pressure and pulse are to be measured immediately and thereafter at 1-min intervals for 4 min post-exercise.
Record the test values on Table 2, and repeat the testing and recording procedure with the second subject

Table 2 Exercise

Harvard Step Test			Interval Following Test
	Baseline		Immediately		1 min		2 min		3 min
	BP	HR pO₂	BP	HR pO₂	BP	HR pO₂	BP	HR pO₂	BP	HR pO₂
Well conditioned
Poorly conditioned

The subject's index of physical Fitness is calculated using the formula below:

	duration of exercise in seconds x 100
Index =	—————————————————
	2 X sum of the 3 pulse counts in recovery

Scores are interpreted according to the following scale:

below 55 poor physical condition	72 to 79 high average
55 to 62 low average	80 to 89 good
63 to 71 average	90 and over excellent

Discussion

When did you notice a greater elevation of blood pressure and pulse? Explain.
Was there a sizeable difference between the after-exercise values for well-conditioned and poorly conditioned individuals? Explain.
Did the diastolic pressure also increase?