If i couldn't take MCV in the dynamic contraction because i have more than athlete and more than eight muscles for measure . what is the best method for that . I have the average level of the muscle activation and max peak value in this area, Should i take a percentage of these data ( average level / Max Peak * 100).
It depends on the purpose of your measurement. I am sure you know the excellent literature that an MVC, even for an isometric contraction, is extremely elusive. Honestly, I don't think it can be done.
Thank you Richard for your answer. Yes i know that is MVC is a better method to normalize EMG signal and i already do it with another measurements . But i was trying to find a soultion to process these data.
Reagards
Mansour, not sure I follow your challenge but I can share something we have come across. Dynamic normalization of the EMG. We collected shoulder muscle activity all day in a field application, we used three reference (submaximal) contractions (RVCs) of the muscle for normalization and to aviod injury. RVCs and MVCs each have their own strengths. However, our subjects were non-native English speakers so the RVCs were rather inconsistent. Since the all day task was the same across all subjects and at a very low level with what we believed to be free of fatigue (and later proved the amplitude and mean power frequency did not change across the day). What we did is normalize the EMG to the 95percentile value in the first half hour of the field activity (the task was very cyclical). Amazingly enough this normalization gave us the lowest variability between subject as far as normalized muscle activity. Not sure if this is what you are proposing but the method may be viable depending on your application and what the subjects did and how standard the tasks were across subjects.
the research question was, what is difference between muscle activity for volleyball player from different level of play.
Thank you Peter for your answer. its really Amazing and more real. Because sometimes EMG measurements is more complicated ( from measure procedure until data processing) alot of filters with different standard however for some reason we cant follow this instruction it take a lot of time especially with a big samples and a lot of muscles. So there was always a solution
But, Mansour, if you are just asking about activity, you can measure only EMG and don't need to normalize, right?
Dr. Richard I am really appreciate what you do to help. but there is a huge standard deviation between muscle activity from different players.
How about normalizing to a ground reaction force or objective kinematic or kinetic parameter?
Dear all, I am very happy for Mansour's question, I understand the aim of question about EMG normalization to help for output data interpretation. The methods of EMG normalization ranked by 1- Isometric actions: maximal voluntary contraction (MVC) for athletes and healthy people, submaximal voluntary contraction (SVC) for instability situations, Reference voluntary contraction (RVC) for disorders or injuries situations; 2- Isokinetic actions: maximal voluntary contraction (MVC); 3- Dynamic actions: Peak Dynamic (PD), Mean Dynamic (MD). I agree with the opinion that prefer the MVC because it is the accurate method in different measurements, furthermore, in sports the player do several trails the MVC is a constant value when processing data of all trials for the same player, but other methods depend on the value of every trial separately.
Dr. Richard L Lieber could I ask you, how can I normalize the muscle activity to ground reaction force or biomechanical parameters?. I think this idea is very difficult and need more studies for validation, because the ground reaction force is value of center of body mass GRF that output mainly from force platform, and the most studies found no significant correlation between GRF and muscle activity. Notwithstanding, If you have any study or evidence about your opinion, it is very good for helping of more data interpretation.
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