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Pressure, Force, Muscles and Massage

By Kristin Shields



TYPE OF ACTIVITY:

  • Hands-on activity
  • Group/cooperative learning

TARGET AUDIENCE:

  • Life Science
  • Biology
  • Anatomy & Physiology
  • Integrative Science 1, 2 or 3

QUESTIONS ADDRESSED:

  • What is pressure?
  • How does pressure relate to force and area?
  • Why is pressure important to a masseuse?

Acknowledgement:

I am indebted to Ken Watkins, a teacher at Vanden High School, for creating and introducing this activity to me.


BACKGROUND INFORMATION:

Notes for the teacher:

  • Instructors should feel comfortable instructing the students on safe use of weights.
  • Students benefit from a demonstration of correct massage technique.

Required of students:

  • Willingness to remove shoes and sock and get their feet wet.
  • Basic understanding of muscle anatomy.
  • Willingness to work together and have physical contact with another student's arm.

Preparation time needed:

Students need access to weights to fatigue their arm muscles. Arrangements to use the school's weights should be made in advance. If this option isn't available, students can fatigue their arm muscles in the classroom using heavy objects.

Class time needed:

Part 1: Pressure exerted on the bottom of feet.-- 1.5 days (footprints need time to completely dry)
Part 2: Massage--1.5 days (part of a class period is spent fatiguing arm muscle one class period should be alloted for massage)


ACTIVITY:

Summary/Abstract:

Our body is constantly being subjected to external forces. The relation between force and pressure is straightforward. The more force that is exerted, the greater the pressure. But the effect of area on pressure is somewhat more subtle. A proper understanding of the concept of pressure is essential to an understanding of most areas of physiology.

The Purpose of this activity is twofold:

  1. It will provide students with a feeling for what pressure is and how it is related to force and area. Students will determine the pressure exerted on the bottoms of your feet under a variety of circumstances. In each case, the force exerted is body weight. But the area over which that force is exerted differs, depending on standing on two feet, one foot or tiptoe (one-foot.)

  2. Through the process of massage students will apply their understanding of forces and pressures to enhance the relaxation of their lab partner's forearm.

Materials needed:

Part 1:

  • bathroom scale
  • drying oven (optional)
  • 3 sheets of paper
  • tray or pan
  • scissors,
  • food coloring
  • balance

Part 2:

  • flat table surface
  • sheet of plastic-1 meter long
  • scented oil
  • soap


PROCEDURE:

Part 1: Pressure exerted on the bottom of feet

  1. Remove your shoes and use the scale to determine your weight. Record result. (This step may be done at any time during the period when the scale is free.)

  2. Fill a tray or pan with tap water to a depth of 2 to 3 mm. Add 25 to 30 drops of food coloring and mix. Place a sheet of paper on the floor near the pan.

  3. Remove your shoe and one sock. Dip your bare foot into the colored water, shake off the excess water and then stand on the sheet of paper. Be sure you put your foot down so that all of it is on the paper.

  4. Blot the excess water from the paper, and set it aside to dry.

  5. Repeat steps 3 and 4, but standing on tip toe this time.

  6. Wash off the coloring and dry your foot.

  7. Initial your two sheets of paper (NOT on the footprint). Then place them in the oven to finish drying.

  8. On a third sheet of paper, draw an outline of the part of your shoe that makes contact with the floor. (cut out this outline).

  9. Determine the mass of the shoe cut out.

  10. Determine and record the mass (to the 1/100 g) of a complete sheet of paper.

  11. When your other 2 sheets of paper are dry, remove them from the oven. Cut out the colored footprint and toe-print. Determine and record the masses of these two cut-outs.

  12. Use the following information to calculate and record your body weight in grams.

(weight in pounds) (453.6 gram)
pound
= weight in grams
  1. Calculate the area (cm2) of the whole piece of paper massed in step 10. The area of a cut-out may be from the following proportionality:

    area of cut-out   mass of cut-out
    area of sheet = mass of sheet


    WARNING: Be sure to show UNITS with each of your numerical values. Examples of units: grams, pounds, cm 2 , etc.

  2. Calculate and record the pressure exerted on the bottom of your feet, toes, etc., under the following conditions:
    1. When you are standing barefoot on two feet. (remember to double the area of your cut-out.)
    2. When you are standing barefoot on tiptoe on both feet.
    3. When you are standing barefoot on tiptoe on one foot.
    4. When you are standing in your shoes on both feet.

Sample Data:

Body weight in pounds =
Mass of full sheet of paper =
Mass of cut-outs (3) =
Calculated body weight (grams) =
Calculated area of each cut-out (cm 2 ) =
Calculated pressure (for each situation, grams/cm 2 ) =

Part 2: Pressure and massage

  1. Prepare the table. Cover table top with the sheet of plastic. Have any oils, towels, etc. you may need ready to use and close at hand. Finger bowls work well for the oils.
  2. The temperature of the room should (ideally) be 70 degrees F or slightly above.

  3. The oils should be mixed and scented.

  4. The masseur or masseuse should have warm hands.

  5. Dip your hands in the scented oils, rubbing them together briskly.

  6. Never pour oil directly on to the skin of the person receiving the massage. Always pour oil on to your hands first. Pour about half a teaspoon of oil on to your hands at a time.

  7. Apply the oil with both palms. Use any kind of simple stroking movement that you want, but make certain that it is both gentle and at the same time very definite and steady. If you do not apply enough pressure your lab partner will complain that it tickles! Hairy arms will require more oil. If you get too much oil in one area you can remove excess oil by using the backs of your hands or arms.

  8. The amount of pressure you will use will vary according to the particular stroke (surface area contact) and on the body location being massaged. Keep your hands relaxed; mold your hands to fit the contours of the body; maintain an evenness of speed and pressure; use your weight rather than your muscles to apply pressure.

DETAILED PROCEDURE ON THE FOREARM

  1. Arrange your lab partner's right arm at his/her side with the palm turned down against the table. Spread oil on the hand, forearm and upper arm.

  2. Place both your hands palms down across your lab partner's wrist, cupping them so that they cover the sides as well as the top of the wrist. Have your hands side by side, with thumbs touching. Glide both hands up the arm (side-by-side).

  3. This stroke is called 'draining'. Raise the arm so that it is standing upright with the elbow still against the table. Now make a ring around the wrist with the thumbs and forefingers of both your hands; tilt your hands away from you so that your palms are facing up as you hold the wrist. Have your thumbs against the inside of the wrist, and have both thumbs touching each other. Now, squeezing lightly with your thumbs and fingers, slide both hands slowly down the length of the forearm as if you were draining it. When you reach the crook of the slide both hands back up again, still keeping your thumbs and forefingers in contact with the skin but now applying NO pressure at all. Repeat several times.

    Why, you may ask, do we use pressure going down but not coming up? The answer is that the veins, which lie closer to the surface of the skin than the arteries, are more directly affected by external pressure. Hence when we 'massage' towards the heart, we are giving an extra push to the blood circulating through the veins towards the heart.

  4. With the arm in the same upright position, place your fingers against the back of the wrist and the balls of your thumbs on the underside of the arm. Repeat several times.

  5. With the arm in the same position, make a loose fist with one hand and lightly massage the crook of the arm-- the inside of the elbow area-- with your knuckles. This is a tender area, so reduce the pressure by reducing the force you are applying. Work in tiny circles over the entire axle area.

  6. Finally, wipe any excess oils from the arm.

Sample Data:

Students can qualitatively compare relative soreness of their arms before the massage, immediately following the massage and days following the massage.

METHOD OF EVALUATION:

Discussion Questions-- Part 1:

  1. How does the pressure exerted while standing on two feet compare with the pressure exerted while standing on one foot?

  2. Compare your results with those of others. Can you find persons who weigh more than you do, but exert less pressure on their feet? Can you find opposite examples, i.e., persons who weigh less than you, but exert more pressure on their feet? How can such results be accounted for?

  3. Does your body sense force or pressure? Think about squeezing a thumbtack.

  4. Which of your calculated pressures is the greatest? Why?

  5. Which exerts less pressure on the ground: a 700 lb. gorilla on roller skates, or an 800 lb. gorilla on identical roller skates?

  6. You want to cross an ice-covered pond in wintertime. Why is the ice less likely to crack if you lie down and crawl, rather than walk across?

  7. Discuss the respective advantages and disadvantages of boots, skis, snowshoes and riding horseback in crossing deep, soft snow.

Discussion Questions-- Part 2:

  1. Describe how the masseuse was able to increase the pressure being applied to your arm.

  2. Describe why the pressure seemed to increase (sensed by the massagee) even though the pressure being applied by the masseuse was constant.

  3. How might this activity be improved?

Extension:

During Part 2 of the activity, students can measure the skin temperature of their arm before and after the massage. Thermistors work well for measuring skin temperature.


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