PHYSIOLOGY OF ACTIVITY

Lab #1 Heart Rate

 

INTRODUCTION:

Heart rate (HR) is an easy way to measure an individual's cardiac function and estimate fitness level. The more efficient the cardiovascular system the lower the heart rate and the greater the stroke volume (amount of blood ejected by the heart with each beat). In terms of exercise prescription it is critical to understand that a linear relationship exists between HR and exercise intensity. HR increases proportionally with the workload (up to maximum levels where HR plateaus). Identifying an optimal workload (target heart rate-THR) at which exercise should be done to improve cardiac efficiency is important. In this lab we will be examining two methods to determine the target heart rate for an individual to improve their cardiovascular system.

PURPOSE: to experience and become proficient in taking heart rate by the use of palpation and auscultation (hearing),

- to determine heart rate in various postures,

- to determine estimated and actual maximum heart rates, and

- to determine target heart rates.

EQUIPMENT: Treadmill, Bicycle, Polar heart rate monitors

METHODS: Methods of Measurement

Arterial locations for taking the pulse by palpation.

a. carotid artery --in the neck, just to the side of the larynx (voice box).

b. brachial artery -- in the upper arm, medial to the inferior third of the bicep

c. radial artery -- lateral side of the wrist.

Taking Heart Rate by Palpation
    1. Responsibilities: You will be responsible for determining the pulse rate of one

other member of your group. Prior to doing this find the above described

pulses on yourself. Use your index and middle fingers. DO NOT use your

thumb since it contains an arterial pulse itself.

b. Heart rate will be taken in the supine, seated and standing positions.

c. After having the subject sit or lay quietly for minutes, take their pulse using the

following technique.
    1. Start the stopwatch on a pulse beat and begin the count with zero. Count the

pulse at one location during a 30 second interval while remaining seated.

e. Record resting heart rates (RHR) on the class data sheet.

Estimate your Maximum HR and Target HR

Calculate your estimated maximum HR (MHR) and target HR (THR) using the following formulas:

MHR = 220- age

THR = (220-AGE-RHR) x 60- 80% + RHR

Exercise Heart Rate to Exhaustion

NOTE:

The safety of the subject should be of utmost importance to the technician administering the test. They should be alert to immediately stop the treadmill should the subject fall, stumble, become dizzy or be at the point of exhaustion. A spotter should be ready to assist the subject

if necessary during the test (for more details refer to Guidelines for Exercise Testing.

Before beginning this section of the lab make sure to stretch and warm-up. This is a maximum test so give it your best.

I. Cycle Ergometer Test

    1. Adjust the seat height of the bicycle to conform to your subject's legs

      2. length. A very slight angle in the knee should be present when the foot is resting on the pedal and at the bottom of a pedal stroke. Make sure the subject is comfortable before the test begins.

      b. The subject will maintain a comfortable pedal RPM .

    2. Begin the test. As the subject begins pedaling set the resistance to

      3. 0.5Kp (by turning the handle until the pendulum indicates 0.5 on the large scale). Allow the subject time to get accustomed to the cadence. Once pedaling at the proper cadence start the timer to begin the test.

    3. When about 40 seconds have elapsed begin preparing to take HR (you

may palpate or auscultate). During the last 15 seconds of each minute

count the number of pulses, multiply by four, and record.

e. Increase the resistance to l.5Kp Repeat steps d and e during subsequent

minutes by increasing the resistance 0.5Kp each minute and taking the

HR during the last 15 seconds of each minute and recording it.

Continue until the subject can no longer maintain the cadence or insists

on stopping. In the latter minutes you may have to vocally encourage

the subject to get them near their maximum.

f. Note the total cycle test time. During recovery allow the subject to

pedal against minimal resistance. Take recovery HR during the last 15

seconds of each minute of recovery until the subjects HR is below

100bpm of resting. Do not allow the subject to perform any duties until

this time.

g. Record the subject's determined MHR (cycle) on the class data sheet

II- Treadmill Test
    1. Subjects may wish to stretch prior to the test. Remind the subject that

      2. this is a test of maximum effort, but the technician will immediately

      stop the test upon their request.

    2. The subject should look straight ahead and not at their feet, and should

      3. concentrate on the treadmill rhythm.

    3. The subject should place their hands on the rails with legs straddling

      4. the belt. Turn on treadmill to warm-up stage. Allow the subject to get

      use to the speed. When the subject is comfortable begin the test.

    4. During the last 15 seconds of each stage try to count the number of

      5. pulses. If you are successful record beats/minute. Each stage will last

      two or three minutes. The Bruce protocol is as follows:

       

      Warm-up 0% grade 2 mph 3 min

      Stage I 10% grade l.7 mph 3 min

      Stage II 12% grade 2.5 mph 3 min

      Stage III 14% grade 3.4 mph 3 min

      Stage IV 16% grade 4.2 mph 3 min

      Stage V 18% grade 5.0 mph 3 min

      Stage VI 20% grade 5.5 mph 3 min

      Stage VII 22% grade 6.0 mph 3 min

    5. During the test talk to and reassure the subject. In the latter stages of

      6. the test frequently inquire whether they can go another stage.

    6. When the subject indicates fatigue the treadmill speed should

      7. immediately be decreased to a walk (3 mph). Immediately and

      accurately determine the maximum treadmill heart rate at this time.

    7. Monitor recovery HR for the next 3 minutes, while the subject either

walks at 3 mph or lies down. Be sure the subject's HR has returned

near resting (with 20 bpm) before they begin any other duties.

 

RESULTS:

1. List the raw scores for each class member and calculate the averages for the class, males, and females for the following measurements: (9 points)

a) Seated RHR

b) Standing RHR

c) Supine RHR

d) Estimated maximal heart rate

e) Calculated target HR

*f) Actual maximal HR for cycle

*g) Actual maximal HR for treadmill

** Note: you will only have data for one or two subjects for f and g; therefore, you may not be able to provide an average.

2. Plot exercise heart rate and RPE x 10 against workload for one

subject's treadmill test. (2 points)

DISCUSSION (4 points each)

1. Compare standing, seated, & supine heart rates. What factors may account for differences in HR with these postural changes? Think in terms of Cardiac Output = HR X SV

2. Compare the actual maximal heart rate (MHR) on the cycle vs. the actual MHR on the treadmill. If a substantial difference exists, how do you explain it?

3. Explain what should happen to one's resting heart rate as they increase their level of physical fitness. Also, explain the

difference between a trained and an untrained person's

response to submaximal exercise.

4. Discuss the relationship between heart rate and RPE. Looking at your graph, does Borg's theory hold true? Do you think the RPE scale is a valuable way for someone to gauge their intensity?

Total points available: 25