Please use the following background information to answer questions 2-4: Jack, a
ID: 3476063 • Letter: P
Question
Please use the following background information to answer questions 2-4: Jack, a student in BIO 131, is the subject for this lab and has his EMG recorded during a maximal contraction. To achieve a maximal contraction, he must lift 45 pounds. Six months later, after working out steadily and maintaining a healthy diet, Jack's muscles are noticeably bigger. He decides to try to elicit a new maximal contraction (and record the EMG), and is now able to lift 60 pounds. 2. (2 points) Compare the EMG recordings for Jack's maximal contraction "before" and after" his 6-month training sessions. Circle the correct answer below: a. The EMGs will have the same amplitude. b. The "before" EMG will have a larger amplitude. c. The "after" EMG will have a larger amplitude. (4 points) After his muscle growth, did Jack need greater or fewer motor units to lift 4s pounds as he did "before"? As a result, would the amplitude of Jack's EMG be larger or smaller compared to the amplitude "before"? Please explain your answer. 3. (2 points) Suppose we take samples of Jack's muscle before and after his training period and look at them under a microscope (note: the samples are the same size). After Jack's 6-month training period, you would expect the "after" muscle sample to contain (circle the correct answer below) 4. the same number of muscle fibers with a reduced amount of thick and thin filaments per fiber. the same number of muscle fibers with an increased amount of thick and thin filaments per fiber. an increased number of muscle fibers with the same amount of thick and thin filaments per fiber. a. b. c.Explanation / Answer
2. The AFTER EMG will have a larger amplitude. This is because of the hypertrophy of muscle fibres which results in higher electrical activity of the muscles.
4 (b) The same number of muscle fibers but with increased ACTIN and MYOSIN filaments. This is because the number of muscle fibers does not increase ( NO HYPERPLASIA ) but the muscle fibers increase in size (HYPERTROPHY)