Softly softly catchy monkey, or something. Getting tyres off is more about brains than brawn, although you'll still need a couple of levers. First off, let out as much air as you possibly can from the tube. Then, starting at the valve, pinch (like a crab) the tyre just off the wire/bead on each side so that it is pushed out of the internal lip of the rim. With the tyre a little more loose in the rim, use one lever to lift they tyre out directly opposite from the valve. If you can't now get a second lever in a couple of inches to one side of the first, go back to the valve and repeat the crab-pinch; you'll feel the bead pop back away from the rim, releasing the tension that stopped you getting the second lever in. Try again with the second lever. Repeat the process until you're tyre is liberated.
Trying to man-handle the tyre out is akin to trying to struggle free from Chinese handcuffs.