I need to know which sEMG descriptors are useful to determine motor unit recruitment or activation of a certain muscle. In our study, we want to see how the pattern of activation / recruitment differs between different inter-electrode distance (IED) and different intensities using an electrostimulator to cause muscle contraction.
In brief, we want to see if different intensities of electrostimulation (50, 75 and 100 mA) with different IED differ in the recruitment of motor units or something similar (i.e., any sEMG useful descriptor for this purpose).
During isometric contraction, more motor units are activated, including inactive units, which leads to an increase of the sEMG amplitude. Greater sEMG amplitudes may indeed occur due to greater motor unit recruitment, Thus, sEMG amplitude can be use as a measure of motor unit activity. However, Vigotsky et al. 2015 suggest, that examining actual motor unit recruitment is elaborate and requires specialized techniques, which entail breaking down an EMG signal into the motor units from which it is created.
I recommend article:
https://www.researchgate.net/publication/286930702_Greater_electromyographic_responses_do_not_imply_greater_motor_unit_recruitment_and_%27hypertrophic_potential%27_cannot_be_inferred
Greetings,
Michał Ginszt
Article Greater Electromyographic Responses Do Not Imply Greater Mot...
Hi Michal,
Thanks for your contribution. I know that sEMG amplitude is widely used for such purpose but also know that examining MU recruitment is not as easy as it looks. I am going to contact the first author of the paper!
Best,
Saúl
The selection of the appropriate electrotherapy device, to establish as correct of a physiological depolarization and repolarization as possible, appears to be one factor, in my opinion, that can be overlooked. Wavelength parameters of electrotherapy systems vary widely, while the motor neuron response is singular. We are currently using a horse model in Vienna to evaluate sEMG signals of a FES electrotherapy system. There is a practitioner in your area who has a FES electrotherapy system you may be interetested in evaluating.
With increasing contraction force, new MUs are recruited and those already active increase their firing rates. Both recruitment and rate coding influences EMG amplitude, so it is not easy to find a descriptor that would be sensitive only to recruitment. Moreover, at higher levels the phase cancellations occur, which causes further complications. I would suggest to critically evaluate methods for analysis of interference needle EMG, e.g. Turns/Amplitude method. There is also a cycle of Kopec papers, where several descriptors of interference EMG were proposed. Unfortunately, the journal where they were published, does not exist anymore, but may be you could find them in some libraries. Here are the references:
Kopec, J. (1993). "EMG-LAB computer system for routine electromyography." Electromyogr Clin Neurophysiol 33(3): 173-184.
Kopec, J. (1997). "Diagnostic value of recruitment order in routine EMG." Electromyogr Clin Neurophysiol 37(2): 111-121.
Kopec, J. and B. Emeryk-Szajewska (2002). ""Functional-QEMG" a new reliable method in daily routine investigation." Electromyogr Clin Neurophysiol 42(8): 495-506.
Some computer simulations would be certainly helpful.
Good luck!
Hi Saul,
In this article we addressed your question experimentally,
https://www.researchgate.net/publication/318744564_Associations_between_Motor_Unit_Action_Potential_Parameters_and_Surface_EMG_Features?_iepl%5BviewId%5D=Ceh18Y1A4CD5OsyOHOeDbsNB&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A318744564&_iepl%5BinteractionType%5D=publicationTitle
Hope it helps !
Ciao
Alessandro
Article Associations between Motor Unit Action Potential Parameters ...
- Badges
- Science topic
- Similar topics
- Force