Name:Date:

Lab:How Do Your Muscles Work?

Introduction:Much of the work of the body depends on the contraction of skeletal muscles. In this experiment, you will first observe the characteristics of muscle contraction and then investigate the effects of two factors that influence the action of your muscles- temperature and fatigue.

Materials:

Dishpan of water

Narrow strip of paper that will fit around upper arm

Ice or snow

Timer (clock, watch, stop watch)

Hypothesis: (____/1 point)Describe what you expect will happen when you flex your muscles using an “If, then” statement.

Procedure:

General Muscle Action: (____/4 points)

  1. Place your fingers along the angle of your jaw just in front of your ear. Grit your teeth and observe what happens to the hardness of the muscles in your cheek. Record what you feel on the outside of your mouth.
  2. ______
  1. What muscle was used while doing this?
  1. With the thumb and little finger of one hand, span the opposite arm’s biceps brachii (from the elbow to as close to the shoulder as possible.) Bend the arm and observe the change in the length of the muscle. Record your observation below.
  1. From the information learned in the video, what can contribute to this change?
  1. Measure the circumference of your upper arm while extended and record below. Clench your fist and flex your bicep record the circumference of your arm after.
  2. Before ______After ______
  1. Describe in words the observations:
  1. What muscles were used to do this?

Effect of Temperature on Muscle Action:

Hypothesis: (_____/1point) Read the procedure below and form a hypothesis using an “If, then” statement.

Procedure:

  1. Count the number of times you can make a fist in 20 seconds. Start with your hands completely outstretched and make a tight fist each time. Do it as rapidly as you can. Record your data.
  2. Now submerge your hand in a dishpan of water to which has been added snow or ice so that the temperature is near the freezing point. Leave your hand in the water for 40 seconds.
  3. Remove your hand and immediately count how many forceful fists you can make in 20 second.Start with your hands completely outstretched and make a tight fist each time. Record in Table 1.

Table1(____/.5 points)

Effect of Temperature on Muscle Action

Temperature of Water / Number of Fists
Room Temperature
Ice Water

Effects of Fatigue on Muscle Action

Hypothesis: (____1 point)Read the procedure below and form a hypothesis using an “If, then” statement.

Procedure:

  1. Wrap a rubber band 2x around your thumb and pointer finger. Count how many times you can open your finger in 20 seconds. Repeat the squeezing nine more time and record the results every time. Do not rest between trials. (Example: Record at 20, 40, 60, etc. seconds)
  2. Your partner should record your data on your table.

Table 2(____2 points)

Effect of Fatigue on Muscle Action

Trail # / Number of Squeezes in 20 seconds / Description of your muscles:
1 (20 seconds)
2 (40 seconds)
3
4
5
6
7
8
9
10

Data Analysis:(_____4 points. In order to receive full credit, you must write in complete sentences)

  1. What is one change you observed in a muscle while it is working?Name the muscle and describe the changes.
  1. What effect did the cold temperature have on the action of your hand muscles? Why do you think this happened? Use the terms skeletal muscle fiber and fatigue in your explanation.
  1. What can be done to prepare your muscles while exercising in the cold?
  1. Jim Fitch decided that his physique left much to be desired, so he joined a local gym. After three months of training, during which he was able to lift increasingly heavier weights, he noticed that his arm and chest muscles were substantially larger. Explain the structural basis of these changes.

Graphing Challenge: In Table 3, make a line graph of your and your partners’ results of the Fatigue experiment (make a separate line for each person) Be sure to create a title and x and y axis labels.

Table 3

Title:

Grading Rubric:

Title / Axis’ Labeled / Variables on correct axis / 2 sets of data represented / Accurate numbering
___/1 / _____/2 / _____/2 / ______/2 / _____/2

What can you summarize about your graph above?(___/.5)

Case Study: Diet, Exercise or both?

In a one-year, randomized, controlled trial, researchers from Washington University School of Medicine in St. Louis evaluated independent and combined effects of weight loss through calorie reduction and exercise in nearly 100 obese older adults with an average age of 70. The study, published in the March issue of New England Journal of Medicine, randomized subjects into one of four groups:

1.Control group – participants of which did not receive any advice to change diet or activity.

2.Diet group – followed a reduced-calorie diet (deficit of 500 to 750 calories per day) with high-quality protein (1 gram per kilogram of body weight per day).

3.Exercise group – maintained weight and exercised three times weekly, which included 90 minutes of aerobic exercises, resistance training, and flexibility and balance exercises.

4.Diet-exercise group – combined weight management instructions and exercise trainings as described in 1 and 2.

To “even the playing field” and reduce confounding variables, the researchers gave participants 1,500 milligrams of calcium and 1,000 IU of vitamin D as supplements per day.

Questions 1-6 pertain to the experiment above. (_____/6)

1)What is the dependent variable in the experiment?

2)What is the independent variable?

3)What is the purpose of the control group?

4)Between what weeks were the greatest changes recorded?

a)0-6

b)6-12

c)They are the same

5)Which of the groups had the greatest success while losing weight?

6)What could you summarize about this experiment?