Hi!
In our psychophysiological stress research, we plan to measure 3 modalities: EDA, ECG, and temperature. However, we also consider EMG as a interesting stress marker. The physiological measurement will last about 20 minutes altogether.
Do you have some experience in measuring EMG (e.g., the activity in upper trapezius muscle) to index stress response to psychological stimuly (e.g., social evaluation, mental load)?
Would you recommend to use EMG signal in a multi-modal assessment of the stress response? Does it provide a valid and reliable measure suitable for indexing the presence (or degree) of acute stress?
Thank you for any relevant advice,
best,
M.
Hello
If the objective of the psychophysiological evaluation protocol is to evaluate the impact of the stressor (arithmetic task, TSST, cognitive task, etc), of course the EMG; but my suggestion is to measure it in corrugator muscle (if it is a psychological task). If the task requires physical activity (increase-decrease) of the muscles to test the effectiveness of some technique, then the trapezius muscle is more appropriate. It depends on the objective of the study (to assess stress, or deactivation of stress, you have to select the stressor and the measure). In my experience I used the EMG for years, but I have seen that it also limits the movement of the spontaneous response to the emotional task. Then I have replaced it with the infrared thermal image and basically the same thing is found: the corrugator muscle increases the temperature when the subject is stressed, the nose decreases the temperature. In press I have some manuscripts sent with infrared thermal image and blood pressure to assess stress-relaxation in both clinical population and healthy subjects. In short, according to the objective of the study (Evaluation of autonomic and somatic activity?) I suggest the EMG.
Article Cram's Introduction to Surface Electromyography, 2nd Edition
Article Psychophysiological facial thermal assessment of the relaxat...
Thank you for your valuable reply,
the thing is that we use Virtual Reality device, so the facial muscles would be inappropriate here. The stress paradigm consists of an exposition to a stressor in VR (height) to participants (with varying fear of height). The movement will be minimized in certain time windows.
The main purpose of the study is to validate it (i.e., does the VR paradigm induce reliable stress response?). But also to see whether physiological response to stress is related to motor regulation during the VR task.
If I may, how big time window would you recommend when using EMG. Is it ok to use a sampling from a 2-3 min. period?
Thank you,
best!
M.
It is a very good objective to validate the psychophysiological effect of VR. It is important to consider the control of movement, because any psychophysiological measure is altered by the single movement. I can suggest the inclusion of respiratory sinus, HRV or blood pressure. Now I dedicate myself to analyze more the response of peripheral temperature with a thermal camera, for example, directly in the nose and maxillary area, they give a lot of information about the autonomic activity of exposure to stimuli with emotional charge.
In the case of using the EMG, the trapezius and / or extensor muscles (in the arm) would be ideal. By steps, my suggestion is an A-B-A design (repeated measures):
1) Phase 0: Stability period of the EMG signal for 5 min. (pre-baseline, that is, the value of the signal is not recorded until it stabilizes, the registration begins).
2) A. Phase 1: A 5-minute baseline is the norm for an original research study. If it was for patients with special conditions (that can not be kept quiet for some reason before the protocol), then a minimum of 3 minutes.
3) B. Phase 2: Your affective task (20 min? - consider something that justifies so much time)
4) A. Phase 3: Recovery, that is, return to the baseline by itself (5min)
Hi again!
Since we use stabilometry, the subject will be required to stand firmly on a predefined (physical and virtual) area. Other physiological measures are going to be included as well, e.g. EDA, ECG (and derived respiration) and peripheral temperature (finger). We also consider some neuroendocrine markers (alpha-amylase, cortisol).
As for the design, we plan to use 4 conditions (time windows).
A - "Baseline" after 10-15 min of resting
B - VR simulation in height = 0
C - VR simulation in height = 20 virtual meters
D - VR simulation in height = 20 virtual meters
Each time window will have ~5 minutes to collect the data. But we might consider also a recovery time block (E), but not sure about it now because we are more interested in stress induction than the recovery (for now).
Thank you for your help!
Martin
Good plan! EMG is recommended to fasic response. The Cram's book of introducction has many value of EMG diferents muscles. I suggest have a period of recovery to all measures (phase E - 5 minutes), to contrast.
Hello M. In my experience of measuring upper trapezius EMG during exposure to an acute psychosocial stressor, some individuals are 'responders' and others are 'non responders' when it comes to their trapeziu EMG. What I mean is that some individuals will exhibit an increase in trapezius EMG during exposure to the stressor (even when they are instructed to stay relaxed) and others will not. This seems to be independent of other markers of the stress response, for example increases in heart rate or blood pressure. So if your question is realted to the motor system at all I think it would be an interesting measure to include. But if you are simply trying to determine if there has been some kind of stress respose I would bear in mind that the motor response seems to vary across individuals.
Regarding sampling period, when you say 2-3 min, do you mean that this is the duration of the sampling period, or do you mean that you would like to start quantifying EMG 2-3 min after the start of the stressor?
Best,
Jen
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