# Lab write up

6 June 2016

Title: Grip Strength and Muscle Fatigue
I. Purpose/Hypothesis: In this lab the subject will grip on a scale that measures the amount of force being put on it. We will observe the change in hand strength during continuous grip over time. Then we will also measure hand strength during rapid, repetitive gripping. I believe that hand strength will weaken during a continuous grip more than if you were to keep a repetitive grip.

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II. Procedure:
1. Connect the Hand Dynamomenter to LabQuest and select a new file 2. Change the time length to 100 seconds, and zero the readings on the hand dnyamomenter 3. Have the subject sit up straight, feet flat on the ground, and elbow at 90 degrees 4. Have the subject grip the sensor with full strength and start recording the data. 5. To retrieve data select the given time intervals on the graph, click Analyze and choose statistics to get the maximum force. (repeat this for every time interval) 6. Highlight 0−90 s on the graph. In the analyze menu select linear and record the slope 7. Do the same for repetitive grip.

III. Data:

Table 1 – Continuous Grip
Time Interval
Max force (N)
Change in Max force (N)
0 – 10s
207.4

20 – 30s
121.5
85.5
40 – 50s
122.5
1
60 – 70s
157.7
-35.2
80 – 90s
148.4
-9.3

Table 2 – Repetitive Grip
Time interval
Max Force (N)
Change in Max Force(N)
0 – 10s
212.2

20 – 30s
144.4
-67.8
40 – 50s
140
-4.4
60 – 70s
140.9
.9
80 – 90s
150.2
9.3

Table 3

Slope
Part 1 – continuous gripping
-.0013901
Part 2 – repetitive gripping
-.001501

IV. Conclusion: I saw that the subject’s grip strength was weakening
drastically towards the end of each trial, but it seemed that the continuous gripping was more tiring than the repetitive gripping. This supports my hypothesis that the muscle fatigue is greater in the continuous grip.

V. Discussion Questions
1. Examine your graph and the data in Table 1. What conclusion can you draw about the number of individual muscle fibers that are firing in the last 10 s compared with the first 10 s? The last 10 seconds had much less force than the first 10 seconds because of the fibers tiring out.

2. Is the change in number of muscle fibers that contract occurring at a constant rate? No, the longer you go the less muscles contract because they are getting tired.

3. Use your knowledge of fast, slow, and intermediate skeletal muscle fibers to hypothesize which fibers are contracting in the first, third, and final 10 s intervals. Fast fibers are used first, then intermediate, and lastly slow fibers.

4. How might you explain the subject’s response to coaching? This should be evident in the last 10 s of data for Parts I and II of the exercise. Discuss the possible involvement of the central nervous system, in addition to the muscle fibers. I think that coaching causes the subject to become aware of his ability and is able to work harder

5. Compare the slopes recorded in Table 3. Give a possible explanation for the difference, if any, in muscle fatigue rates seen in continuous versus repetitive gripping. There is a higher declining rate of muscle contraction in the continuous gripping than in repetitive gripping, meaning there is more work done in continuous contraction.

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