It is not clear to me what you want to identify.
You can easily identify the starting and ending points of the force signal using the islocalmin function twice, using 'FlatSelection','first' with the first call to it, and 'FlatSelection','last' in the second call to it.
With respect to ‘the second peak’, both islocalmax and findpeaks would work similarly. Identify the peal with'MinProminence' or 'MinPeakProminence' (depending on the function you are using), and then use either 'MinSeparation' or 'MinPeakDistance' to only return the information for the first peak in a specific interval.
It would be easier to describe this (and possibly write specific code) if I know what you want and if I have your data to experiment with.
.
