Can we feel sinusoid?
You can "feel the sinewave" to the extent that, if variations in voltage are slow enough, then there will be a change in sensation as voltage and/or current vary across a certain range of values. 

The actual signal amplitude range where variations will be felt will vary with points of application, skin resistance, person involved and more. Very low voltage signals may not be felt at all. Very high amplitude signals (eg 300 V peak sine wave at 1 Hz). would probably be felt as if 300V DC with polarity changed every 0.5 seconds was applied -you MAY feel the zero crossings as 2 Hz pulses amidst the pain.

However, if you apply a signal such that at peak voltage you get significant but not overposering muscle contractions then you are liable to feel the variation in contractions at a 2 Hz rate. 2Hz for a 1 Hz signal as positive or negative 1/2 cycles will probably have much the same effects).