IME549 – Industrial Ergonomics
Grip/Pinch Strength Lab Exercise
Introduction: Physical Ergonomics is the science and study of using appropriate work postures to reduce the strain on workers which in return will maximize productivity. This grip strength experiment measures the maximum grip strength capability and EMG generated between the neutral and flexed wrist position as well as between genders. The goal is to show how posture affects force capability, which affects worker performance as well as corresponding muscle activity. Therefore hand tool and job design should be designed accordingly as to maximize production. Materials:
* DataLog (Biometrics, LTD, Model W4X8), Bluetooth technology, to record data * Biometrics Data Analysis Software, Version 7.0, to analyze grip strength and EMG data * P100 Pinch grip dynamometer (Biometrics, LTD) to measure pinch grip strength (collected at 50 Hz) * G100 Power grip dynamometer (Biometrics, LTD) to measure power grip strength (collected at 50 Hz) * SX230W EMG electrode (Biometrics, LTD) to measure electrical muscle activity (collected at 1000 Hz) *
R206 EMG ground strap electrode placed over the elbow (Biometrics, LTD)
Methods: The first step is to prepare the subject for the experiment. After letting the subject know what data you intend to collect and how you will collect it, you need to make sure there are no previous wrist or hand injuries such as carpel tunnel. If so, let the patient know that they are not eligible for testing because administering the experiment could lead to injury. After verifying that your patient is fully aware of the procedure and that there are no previous condition that could alter the experiment, prepare the subject. Since this was a simple lab experiment, we did not clean or prepare the skin for subjects. If this was a more in depth lab, it’s suggested to fully clean the skin of any contaminants and to prepare the skin by minor abrasion as to acquire to most accurate EMG readings. Set the subject in the testing chair and get ready to apply all the testing sensors. The first sensor is the external EMG electrode which is secured via double sided tape. Placement of the external EMG sensor should be ¼ the distance from the Humeral Medial epicondyle to the Styloid Process on the Radius side (see attached diagram) of the subject’s dominant arm. After marking the placement, we had the subject keep their finger on the location, prepare the EMG sensor. Place the double sided tape onto the EMG electrode and place at the marked location. The EMG electrode should be placed with the marked spot between the two sensors and be oriented parallel to the muscle fibers. The EMG electrode will collect electrical muscle activity at a rate of 1000 Hz/sec. Do not plug the EMG electrode into the DataLog reader just yet. Next on the list is to secure the R206 EMG ground. This sensor should be placed on the Humeral Medial epicondyle from which you measured in the previous step. Make sure the sensor is secure and has a snug fit. The subject now has all of the appropriate and required sensors needed for the experiment/data collection. The EMG ground should remain unplugged for now, just like the EMG electrode. Open up your Biometrics Data Analysis Software. We will now zero out the DataLog to acquire the most accurate readings. With the EMG electrode and ground still unplugged, go to the ‘Set Up’ tab on your software. Select Analog Input. The “Flexors” or EMG ld be collecting at 1000Hz/sec and the dynamometers should collect at 50Hz. Once you have verified these collection rates, click ‘Zero All’ and then OK. The DataLog is now zero’d out and you can plug in the EMG electrode and ground into their respective ports. The Dynamometers should be plugged in at this point at well. You are now ready to start collecting EMG and dynamometer data. Press the ‘S’ key to...
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