Many individuals believe that lactic acid can cause sore muscles for days after exercise. Soreness from exercise actually comes from the small tears in the muscle that are in need of repair, as well as intercellular components that spil into the extracellular spaces where these small tears occur. The soreness may last anywhere from 1-5 days depending on the physical fitness of the individual. Scientists have found that the body uses lactic acid for energy and breaks down within 30-60 minutes after very intense exercise. PROCEDURE In this exercise, muscle fatigue will be demonstrated by lifting a heavy object. A partner or family member may be required to assist with this exercise 1. Before beginning, set up a data table similar to the Data Table 5 in the Lab Report Assistant 2. 3. 4. 5. section to record observations while performing the experiment Obtain the stopwatch from the LabPaq Retrieve the Anatomy and Physiology textbook (or other heavy textbook) Record a zero “O” in the start time column for Trial 1 into Data Table 5 Stand up and extend an arm straight out in front of you (DO NOT BEND YOUR ELBOW AT ALL) so that the arm is parallel to the floor. 6. Hold your hand out with your palm flat and fingers straight. Place your A&P text in your hand and immediately start the stopwatch 7. Hold the book straight out in front of you until the arm starts to ache or burn. Ask the partner to record this time into Data Table 5 as “Aching/Burning Feeling Begins.” 8. When the arm begins to drop, ask the partner to record the final time as “Arm Begins to Drop seconds 9. Put down the book and begin the rest period. Rest for one minute 10. Repeat Steps 4 through 9 twice more, for a total of three trials. Record the data for Trials 2 and 11. Calculate the total time in seconds required for each trial and record this under “Duration” in 12. Plot a graph for the total time it took for fatigue to set in for each trial. Label the horizontal 3 next to “2” and “3” in Data Table 5, respectively. Data Table 5 axis as “Trial” and the vertical axis as “Time in Seconds.” 220