I would use a Butterworth or Chebyshev Type II filter with a passband of [1 100] Hz and a stopband of [0.5 120] Hz, a passband ripple of 10 dB and a stopband ripple of 40 db. (Both of these filters have a flat passband, so the value of the passband ripple is in practice irrelevant.)
Remember that you have to normalise the passband and stopband frequencies by the Nyquist frequency, the reason you are likely filtering out much of your signal now:
Fs = ...; % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
Wp = [1 100]/Fn; % Normalised Passband
Ws = [0.5 120]/Fn; % Normalised Stopband
This is my typical filter for EKGs. It may be necessary to tweak it depending on the sampling frequency, since a sampling frequency ‘Fs’ >200 Hz is best, and 250 Hz is usually the most efficient. If your sampling frequency is lower than 200 Hz, you will have to reduce the upper passband and stopband frequencies of the filter accordingly.
