Various studies have shown that intensified training results in reduced EMG activity performing a standard assessment. But why is that so at the same power output? If cycling @ 200W then EMG activity is lowered in VL for example in an overreached scenario.
Do you mean - more muscle fibers need to be activated because the activity in the muscle fibers you are analysing with EMG have downgraded activity levels due to fatigue. Hence the need to bring in more high threshold motor units to deliver the amount of work required. I assume the EMG activity only picks up a small portion of the muscle group?
Hi Allan,
I think there could be two more reasons.
1st if training resulted in more ST-fibers and more ST-fibers are used during respected tasks (E.g. ergometry at 200W) then EMG would be lower due to better mechanical efficiency of ST-fibers compared to FT-fibers.
2nd it might be a coordination effect. If coordination is better after training EMG should be lower at same absolute intensities due to better mechanical efficiency.
I think you should follow the activity for minimam one minute under loading. To see the fatiuge slope for muscles. Then you can see the change ratio of the activity from start to end.
This is specifically in athletes who are over-reached and thus may report a higher RPE for the 200W bout but yet ECG activity is reduced - training effect would not be relevant as these athletes would be highly trained and certainly have undergone maximal fibre conversion. Would extra fatigue lead to increased muscle co-ordination and hence reduced EMG?
Hi Alan,
I believe it is a repetitive type of work.
I found frequency analysis of EMG signal is more reliable than amplitude analysis while doing repetitive type of work. Then calculate the centre frequency . Centre frequency decreases with time (till fatigue). Slope will be higher for higher load as suggested by Mansour Attaallah. I have published two papers in this area: (a) fatigue at different hand position and (b) fatigue recovery due to rest period.
Amplitude analysis of EMG signal is better for isometric contraction.
I agree with Keshaba. FFT analysis is better to determine fatigue status.
Thankyou for all your replys - Im not asking for a method but for a physiological reason for this phenomona? Why does EMG activity reduce for the same work output in fatigued athletes?
Which Parameters are reduced? Amplitude, time (contraction), Area under curve...Specify your data (if it is yours), so one can get a better understanding
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