Analysis & Questions

Analysis:
Conversion of Moments from the measured axes to the center joint axes:
Mx'=Mx + Fy*d
My'=My-Fx*d
Mz'=Mz
Fx'=Fx
Fy'=Fy
Fz'=Fz'
d=0.1204

1. The six-axis forces and moments measured during the MVC are with respect to the geometric center of the force sensor. Data for the maximal voluntary contraction (MVC) are saved in _____.What are the corresponding force and moment measurements with respect to the center of the elbow joint for each trial? Compare the "off-axis" torques before and after the transformation, and compare the amplitude of the major elbow flexion torque with the "off-axis" torques after the transformation.

2. What is the maximum flexion torque during the MVC? While the subject generates MVC flexion torque, how much "off-axis" torques are generated about the other two axes of the elbow joint in each trial(supination-pronation and varus-valgus)?

3. Matrices bic_raw and bic are the raw (unprocessed) and linear envelope of the Bicep EMG signal, respectively. Data on the EMG is in _____ Plot the the EMG linear envelope using the Matlab command plot(bic). What is the maximum amplitude of the EMG signal during the MVC in mV in each trial?

4. Plot the mean isometric flexion torque(Mz) versus the mean EMG linear envelope(bic) during the target matching tasks over various torque levels(EMG-Torque relationship), and fit it with a straight line (need help with curve-fit? check out a Matlab example). Data on the EMG-torque relationship are in ______. A time window you can use (with steady torque level) is from the 3000th to 4000th data points.

5. Plot the flexion torque and the biceps raw EMG signals as a function of time over the 180 sec fatiguing exercise. Data on muscle fatigue are in ________. Do a spectral analysis for two contraction periods near the beginning and end of the fatiguing exercise, respectively. Plot the two power spectra together. Analyze the spectrum of the raw EMG signal and compare between two contractions (e.g., the first and last contractions in Trial 1 with range1=1000:3000; range2=35500:38000,compare bic_raw(range1,1) vs. bic_raw(range2,1)). What differences do you see between the two curves?
Hint: refer to the following example Matlab program. You can use on-line help provided in Matlab (e.g., "help spectrum").

* For data in Matlab format, each column represents a trial (if there are multiple trials) and each row corresponds to a data point within a trial.

Questions:
1. How does the skin movement over the muscles affect the EMG signal?
2. What is a typical cause of noise in the data and how can you correct it?
3. How does fiber orientation affect placement of the electrodes?
4. If you were testing the contraction in the leg, on what muscles would you place the electrodes in the thigh?

1. Document general methodology and procedure.
2. Submit your figures of the EMG analysis. If multiple trials are performed for the same task during the actual experiment, only one representative set of figures is needed.
3. Hand in a detailed analysis of the figures derived from the Analysis of the data
4. Answer all questions

Sample Analysis
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