@TeeKay6 @Vinnie90
Afternoon chaps, bet you didn't think you'd hear from me again. Today I finally managed to get some time to work on this project. I started by putting a band pass filter on each of the 2 muscle signal inputs but not the reference. I checked that they worked first with a function generator and they did so I connected them up to the INA. I also set the gain to ~160 as by my calculations the amplifier was only increasing the signal to about 1.6V at its peak. Anyway, I have a circuit together now with band pass filters on each muscle input to keep the signal to ~5-500Hz but I'm still not getting a signal that increases and decreases with muscle contractions. I've attached an image of the circuit diagram, the output on my oscilloscope and the layout on the breadboard (Not that the last one will probably help much). The 10uF caps are electrolytic for no reason other than they were within arms reach at the time. The 0.1uF caps are ceramic.
Tah

 

@TeeKay6 @Vinnie90
Afternoon chaps, bet you didn't think you'd hear from me again. Today I finally managed to get some time to work on this project. I started by putting a band pass filter on each of the 2 muscle signal inputs but not the reference. I checked that they worked first with a function generator and they did so I connected them up to the INA. I also set the gain to ~160 as by my calculations the amplifier was only increasing the signal to about 1.6V at its peak. Anyway, I have a circuit together now with band pass filters on each muscle input to keep the signal to ~5-500Hz but I'm still not getting a signal that increases and decreases with muscle contractions. I've attached an image of the circuit diagram, the output on my oscilloscope and the layout on the breadboard (Not that the last one will probably help much). The 10uF caps are electrolytic for no reason other than they were within arms reach at the time. The 0.1uF caps are ceramic.
Tah

1. The scope shows what I believe to be 50Hz pickup from your mains. You will have to shield your circuitry within a metal container that is grounded (unless the 50Hz signal is via your power supply).
2. The filter caps could be problematic. Ceramics are often microphonic (respond to vibrations/pressure). Electrolytics have high leakage and often considerable dielectric absorption (i.e. they never completely discharge). Film caps for both would be a better choice.
3. The 3K resistor to ground in your filters is much too low; you would short out any signal coming from a muscle. Recalc for a resistor of 300K or more.
@Rossosaurus
Update: It remains doubtful that you can use high value resistances with the INA126's high input bias currents. An INA with low bias current would be preferable.
3. If you connect your 3 inputs together, what output results? It should of course be zero.

 

@TeeKay6
Hi there, Good news! I think this thing actually works. I've attached a video of the circuit functioning and it definitely seems to increase when I tense my bicep. I changed high pass filter to something with a resistance of 300K and now it works. I will probably still do as you say and switch to an amp with a lower input bias, probably the AD8220, and buy some film caps. I also printed a battery holder for my Arduino as I assumed like you did that the 50Hz was coming from the mains and am now running it off a battery but it still reads 50Hz. I will start work on the precision rectifier now and report back.

http://imgur.com/EbE7JZm