The definition of electromechanical delay here is the time delay between the M wave which
is stimulated by ES and the onset of force.
Finding force onset is pretty easy. I just found the point which is double standard deviation of
the baseline force.
However, finding M wave onset is a little bit difficult. I made two definition to find the onset
point. One is the location of point should be in front of the location of Max peak and Min peak of M wave.
The other is the point should be zero after differential.
