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6.Chronic headaches and temporomandibular disorders (TMD) may be the result of unconscious clenching of the jaw. What are some ways to reduce/prevent jaw clenching?Lab 6: EMG and Muscle Fatigue
PURPOSEThe purpose of the lab is to obtain representation of the electrical activity of a muscle, correlate grip strength measurements with electrical activity data, correlate measurements of grip strength and electrical activity with muscle fatigue, and observe the effect on grip strength of a conscious effort to overcome fatigue. MATERIALSANDMETHODSMaterials:Lab handout, Vernier EKG sensor, electrode tabs, Vernier Hand DynamometerMethods:Select one person from your lab group to be the subject.Part I Grip Strength without Visual Feedback1.Connect the Hand Dynamometer to LabQuest and choose New from the File menu.2.On the Meter screen, tap Length. Change the data-collection length to 100 seconds and the data-collection rate to 100 samples/second. Select OK.3.Zero the readings for the Hand Dynamometer.aHold the Hand Dynamometer along the sides, in an upright position (see Figure 2). Do notput any force on the pads of the Hand Dynamometer.bWhen the readings stabilize, choose Zero from the Sensors menu. The readings for the sensor should be close to zero. 4.Attach three electrode tabs to one of your arms, as shown in Figure 3. Two tabs should be placed on the ventral forearm, 5 cm and 10 cm from the medial epicondyle along an imaginary line connecting the epicondyle and the middle finger. 5.Attach the green and red leads to the tabs on ventral forearm. For this activity, the green and red leads are interchangeable. Attach the black lead to the upper arm.6.Have the subject sit with his/her back straight and feet flat on the floor. The elbow should be at a 90° angle, with the arm unsupported. 7.Have the subject close his/her eyes, or avert them from the screen.8.Instruct the subject to grip the sensor with full strength and start data collection. The subject should exert maximum effort throughout the data-collection period.9.At 80 s, the lab partner(s) should encourage the subject to grip even harder. Data will be collected for 100 s. 10.Use the force vs. time graph to determine the mean force exerted during different time intervals.dTap and drag across the data from 0 s to 20 s.eChoose Statistics from the Analyze menu. fRecord the mean force in Table 1, rounding to the nearest 0.1 N. gChoose Statistics from the Analyze menu to turn off statistics.
11.Repeat Step 10 for two other 20 second intervals: 60−80 s and 80−100 s.12.Repeat Step 10 to record the maximum and minimum mV during three intervals on the EMG graph: 0–20 s, 60−80 s, and 80−100 s. Rounding to the nearest 0.01 mV.13.Calculate the difference between each minimum and maximum value and record this value inthe ∆mV column in Table 1.Part II Grip Strength with Visual Feedback14.Have the subject sit with his/her back straight and feet flat on the floor. The Hand Dynamometer should be held in the same hand used in Part I of this experiment. Instruct the