To put this in context, I'm looking to achieve both high speed and high accuracy for measuring biosignals through the FFT. I'll describe a quick example to see if I understand this properly as well as to illustrate my question. So, if I have this correctly, if I wanted to take a low-frequency FFT, say frequencies 0-64 Hz for example, to mmeet the Nyquist criterion my sampling frequency would have to be at least twice that, thus 128 Hz. Then, if I wanted a frequency resolution of 1 Hz to one bin, I would need 64 bins, which would put me at 128 samples because there are both real and imaginary parts. Therefore, to achieve that 1 Hz resolution, I would be presented with having a sampling rate of only 128 Hz while needing to take 128 samples, which would put me in the position of having only 1 full performance of the FFT for every second of time that elapses.
Ultimately, this leads me to my real question: at low frequencies, is it possible to take a high resolution FFT (say 1 or 2 Hz per bin) while still maintaining some semblance of speed? Or is this simply impossible due to the limitations of the transform? If so, is there some alternative method or some sort of compromise to be made between resolution and speed? As an aside, I read an article a while ago about oversampling and throwing out samples at certain integer multiples past a certain point (or something like that, sorry it was a little while ago) in order to speed up the sampling process. Maybe somebody knows what that is (or maybe I'm jut rambling at this point). Either way, thanks for any help you can provide in advance.