When you are physically active, your pulse rate tends to be higher than when you are inactive. The more intense your activity, the higher your pulse rate tends to be.

When you maintain your physical activity at a constant level (for example, when stepping up and down on a step at a constant rate, or walking up a uniform incline at a constant speed), your pulse rate will become fairly stable after a few minutes.

Under these circumstances, your pulse rate is a good indicator of the rate at which you are metabolizing oxygen as you deplete your body's glucose reserves.

Since your physiological responses are complex, the relationship between the rate of oxygen metabolism and your pulse rate is not perfectly linear, but overall the relationship tends to be reasonably close to linear.

The amount of blood pumped per heartbeat is nearly the same at different pulse rates, but there are small differences due to a variety of physiological factors, including blood pressure, the compliance of the heart tissues, and others.

The concentration of oxygen in blood coming from the lungs tends to be about the same for different pulse rates, but small differences do occur at different pulse rates and with different types of activity. The same can be said for oxygen returning to the lungs.

If the amount of blood per heartbeat, the concentration of oxygen in the blood entering the lungs, and oxygen concentration as blood leaves the lungs, were all perfectly constant, then (barring some kind of oxygen leak from the blood, which doesn't happen, or significant blood loss, which can't be sustained) the rate at which oxygen is metabolized will be linearly related to pulse rate.

In this experiment, you will correlate your pulse rate with various measures of your activity rate.

Activity that influences pulse rate comes from moving various objects and body parts, and from pushing and pulling on things. The activities used in this experiment are therefore chosen so that as many as possible of the following can be measured with a reasonable degree of accuracy:

forces (at least average forces) exerted

distances moved

time

pulse rate.

Pulse rate will be correlated with various combinations of these quantities. We will determine whether and how many of the following are related to pulse rate:

force alone (i.e., force independent of distance and time)

distance alone (i.e., distance indepent of force and time)

time alone (i.e., time independent of force and distance)

the product of force and distance (i.e., force * distance independent of time)

the product of force and time (i.e., force * time independent of distance)

the quotient force / time (i.e., force/time independent of distance)

the product of distance and time (i.e., distance*time independent of force)

the quotient distance/time (i.e., distance/time independent of force)

the product of force, distance and time

the quantity force*distance/time

the quantity force/distance/time.

Pulse rates will be observed as you:

Step up and down at various rates on one or more steps.

Pull at a constant velocity against various resistances.

Pull at different velocities against a constant resistance.

Run back and forth at various frequencies between two points.

Repeatedly extend and release an elastic spring.

Walk at various speeds up a steady incline.

Opening Question: Suppose that I asked you what my pulse, or your pulse (whichever you would rather think about) would be after climbing a hill 200 feet high. What other information would you need to have in order to make a reasonable conjecture? What is the minimum number of questions you could ask to obtain sufficient information?

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Predict your pulse rate for each of the following situations, and sketch the indicated graph. You may if you wish try a few of these to get a feel for how your pulse rate various with different situations, but you should be able to imagine most of these situations. Pay close attention to how you would expect the pulse rate to vary for different activity levels in each group. Assume that each activity is maintained for at least 5 minutes. If you think that an activity is too intense for you to maintain for 5 minutes, make no prediction for that activity.

Group 1.

You step up and down on an 8-inch-high step at each of the following rates:

5 steps/minute

10 steps/minute

15 steps/minute

20 steps/minute

30 steps/minute

40 steps/minute

50 steps/minute

60 steps/minute.

Sketch a predicted graph of pulse rate vs. stepping rate.

Give your predictions and describe your graph.

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Group 2.

You walk or run up and down a flight of 8-inch-high steps at each of the following rates:

5 steps/minute

10 steps/minute

15 steps/minute

20 steps/minute

30 steps/minute

40 steps/minute

50 steps/minute

60 steps/minute.

Sketch a predicted graph of pulse rate vs. stepping rate.

Give your predictions and describe your graph.

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Group 3.

You pull for a distance against a 20-pound resistance at the following rates:

25 feet/minute (125 feet in 5 minutes; a turtle's pace)

50 feet/minute (250 feet in 5 minutes; a very slow stroll)

75 feet/minute (375 feet in 5 minutes; a slow stroll)

100 feet/minute (400 feet in 5 minutes; a slow walk)

200 feet/minute (800 feet in 5 minutes; an easy walk)

300 feet/minute (12000 feet in 5 minutes; a standard walk)

400 feet/minute (1600 feet in 5 minutes; a fast walk or slow jog)

500 feet/minute (2000 feet in 5 minutes; a jog)

600 feet/minute (2400 feet in 5 minutes; a fast jog)

700 feet/minute (2800 feet in 5 minutes; a slow run).

Sketch a predicted graph of pulse rate vs. walking rate..

Give your predictions and describe your graph.

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Group 4.

You pull at 100 feet/minute (a slow walk) against the following resistances:

5 pounds

10 pounds

20 pounds

30 pounds

40 pounds

50 pounds

60 pounds

70 pounds

80 pounds

90 pounds

100 pounds.

Sketch a predicted graph of pulse rate vs. resistance..

Give your predictions and describe your graph.

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Group 5.

You walk, run or jog up a hill with a 10% grade (about as steep as the roads get around the VHCC campus) at the following rates:

1 mph (a very slow walk)

2 mph (a slow walk)

3 mph (a moderate walk)

4 mph (a fast walk)

5 mph (a slow jog)

6 mph (a regular jog)

7 mph (a fast jog)

8 mph (a slow run)

9 mph (...

10 mph (...

Sketch a predicted graph of pulse rate vs. your speed.

Give your predictions and describe your graph.

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Group 6.

You run back and forth between two points 12 feet apart (the width of an average room) with the following frequencies:

4 round trips per minute

6 round trips per minute

8 round trips per minute

10 round trips per minute

12 round trips per minute

14 round trips per minute

16 round trips per minute

18 round trips per minute

20 round trips per minute.

Sketch a predicted graph of pulse rate vs. frequency.

Give your predictions and describe your graph.

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Setting up and collecting data.

Measure the vertical or horizontal rise of a step you have chosen for this experiment. You should choose a step approximately 6 inches high.

Distance students: You are the subject, unless you can find a volunteer. Work only within your physical comfort range, and if you have any physical limitations at all that interfere with performing this experiment, contact the instructor. You will be provided with data from another student, or with simulated data.

Determine the desired stepping rates for the subject, and adjust the length of a pendulum to model the different rates:

You will time each stepping rate with a pendulum.

Determine by trial and error the approximate stepping rate, in beats per minute, at which the subject's pulse after at least 3 minutes of stepping will be 20 beats per minute greater than his or her rest pulse.

Let the pendulum swing through a complete cycle (both back and forth) as the subject steps up, and again as the subject steps down. Adjust the length of the pendulum until the subject achieves the desired pulse rate.

What is the subject's pulse rate, and what is the length of the pendulum?

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You have determined the number of steps per minute necessary to increase the subject's resting pulse rate by 30 beats per minute. You will perform a number of trials, each of which increases the stepping rate by about half this many steps per minute. (For example, if a stepping rate of 12 steps/minute was required to elevate the subject's pulse rate by 20 beats/minute, then the stepping rate should increase from trial to trial by 6 steps/minute).

Figure out how many steps per minute will be required for each trial. There should be approximately 5 trials.

Determine the corresponding series of pendulum lengths to use in order to obtain the desired stepping rates. Use paper clips or knots to mark these lengths.

Give a table of the desired stepping rates and pendulum lengths.

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Obtain pulse rate vs. stepping rate data:

Pulse timing must be completed within 20 seconds after stepping ceases, so practice beforehand to get comfortable with the process of finding and timing the pulse within these time constraints. If timing is not accurately completed within 20 seconds, repeat the 3 minutes of stepping and time again.

Have the subject begin stepping at the first rate, and continue for at least three minutes. Use the pendulum to keep the subject stepping at the prescribed rate. Then find the subject's pulse rate by timing his or her pulse for 10 seconds.

Repeat for each subsequent stepping rate. Stop when the subject begins to feel moderate discomfort, or when the maximum safe heart rate of .8(220 - subject's age) (around 160 for a 20-year-old) is reached. For each trial, record pendulum length, stepping rate and pulse rate.

Enter the pulse rate vs. stepping rate data.

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Do steppping rates seem to change from data point to data point by about the same amount? Does it seem, allowing for the unavoidable errors in your observations, that pulse rate tends to increase by about the same amount from data point to data point?

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Sketch a graph of pulse rate vs. stepping rate. Clearly label the graph.

Is there a clear tendency for the graph to curve either upward or downward, or is it plausible that the overall tendency of the graph is to form a straight line?

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Explain how this fact makes it clear that force alone does not determine your pulse rate.

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The duration of your effort was 3 minutes for every trial.

Explain how this fact makes it clear that duration alone does not determine your pulse rate.

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Do you think it would have made a significant difference in your pulse rate to have continued for 5 minutes instead of 3 on every trial? Do you therefore conclude that duration (beyond 3 minutes) has a significant effect on pulse rate? How could you design an experiment to prove or disprove your conjecture?

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Assuming that you made the same motions with each step, varying only the speed with which you made those motions, the force required to lift your weight was exerted through the same distance on every step (we haven't proved this here; accept it for the moment and be ready to test it later).

How was the total distance related to the stepping rate?

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How was the observed pulse rate therefore related to the distance?

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In this experiment you will move at a constant speed while exerting a measured force against resistance.

 

The force may be exerted to drag some object, or against the resistance of other individuals who are pulling against you, or even against a vehicle which is moving at constant speed.

 

The force may be measured by spring balances or by other means.

Obtaining the data

Use a force equal to about 1/8 of the subject's weight. If the subject is in very good physical condition, double this force could be used. If the subject cannot easily perform the first trial of this experiment with a force equal to 1/8 of his or her weight, that subject should not be a subject for this experiment.

Mark off a path at intervals of 2 meters. These intervals will be used to keep the subject moving at a constant pace.

The subject will begin by pulling against the resistance (not carrying the weight; pulling against the specified resistance) for 3 minutes while moving at a constant rate of 1/4 meter/second. This means that it should take the subject 16 seconds to pass from one mark to the next.

At the end of 3 minutes, quickly determine the subject's pulse rate.

Repeat, this time moving at 1/2 meter/second.

If the subject's pulse rate at 1/2 meter/second has risen less than 20 beats/minute from resting rate, increase the speed by 1/2 meter/second in each subsequent trial. Otherwise increase by 1/4 meter/second.

Continue to increase the speed, by either the 1/4 or 1/2 meter/second increment, and continue 3-minute trials until the subject's pulse rate is greater than the maximum comfortable rate for the indivicual (about 140 if the subject does not exercise vigorously on a consistent basis, or 160-170 if the subject does exercise vigorously and consistently).

Give your data.

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Analyzing the data

Make a table of pulse rate vs. the subject's speed. Clearly label the table and attach a brief explanation of what the data is about.

The subject's speed changes from data point to data point by about the same amount. Does it seem, allowing for the unavoidable errors in your observations, that pulse rate tends to increase by about the same amount from data point to data point?

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Sketch a graph of pulse rate vs. speed. Clearly label the graph.

Is there a clear tendency for the graph to curve either upward or downward, or is it plausible that the overall tendency of the graph is to form a straight line?

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Quantities associated with pulse rate

The force required to pull the weight is the same at any speed. Explain how this fact makes it clear that force alone does not determine your pulse rate.

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The force was exerted through a different distance on every trial.

How was the total distance related to the subject's speed?

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How was the observed pulse rate therefore related to the distance?

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Would the pulse rate have been significantly affected if the speed had remained the same, but the distance changed (assuming that the duration is at least 3 minutes)?

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Would the pulse rate have been significantly affected if the distance had remained the same but the speed had been decreased?

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Does the pulse rate, for a constant force, depend on distance alone, on duration alone, or on speed?

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In this experiment you will pull the same object as in the preceding experiment, but you will maintain a constant speed of 1 meter / second while applying different forces.

 

Start with a force of about 5 pounds (about 2.5 kilograms or 25 Newtons) and a speed of 1 meter per second. Continue for 3 minutes and take the pulse.

Increase the force to about 10 pounds (5 kg or 50 Newtons) and repeat.

Then use 15, 20, 25 pounds, etc. until the maximum safe heart rate is reached (see previous experiment). Keep the speed at 1 meter/second for every force.

Analyzing the Data

Make a table of pulse rate vs. the applied force. Clearly label the table and attach a brief explanation of what the data is about.

The applied force changes from data point to data point by about the same amount. Does it seem, allowing for the unavoidable errors in your observations, that pulse rate tends to increase by about the same amount from data point to data point?

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Sketch a graph of pulse rate vs. force. Clearly label the graph.

Is there a clear tendency for the graph to curve either upward or downward, or is it plausible that the overall tendency of the graph is to form a straight line?

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The speed with which the weight is pulled is the same for every force.

Explain how this fact makes it clear that speed alone does not determine your pulse rate.

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Estimate the pulse rates you would expect if the subject pulled the weight 400 meters at a constant velocity, covering the distance in 10 minutes, in 9 minutes, in 8 minutes, in 7 minutes, in 6 minutes, in 5 minutes, in 4 minutes and in 3 minutes.

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Collect and Analyze Data

Perform this experiment. Record the pulse rate corresponding to each time. As usual, do not exceed safe heart rates. Analyze and determine what sort of effect the time in which a given number of steps are made has on pulse rate.  Give your data.

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What combination of force, distance and time determines pulse rate?

Other things being equal, what effects do force, distance and time have on pulse rate?

For a given distance and time (e.g., 400 meters and 7 minutes), will increased force tend to increase or to decrease pulse rate?

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For a given force and time (e.g., 20 pounds and 7 minutes), will increased distance tend to increase or decrease pulse rate?

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For a given force and distance (e.g., 20 pounds and 400 meters), will increased time tend to increase or decrease pulse rate?

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Which of the following quantities would you most reasonably expect to have a linear relation to pulse rate?

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force * distance * time

force * distance / time

force / distance / time

force / distance * time

force + distance + time

force + distance - time

force - distance + time

force - distance - time.

For each possibility, either describe a situation which shows that the quantity could not possibly be linearly related to increased pulse rate, or explain why it should be so related.

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Does the pulse rate, for a constant force, depend on distance alone, on duration alone, or on speed?

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