i used to do a really good exercise - it's really hard though. i read it in a horse magazine years ago i wonder if anybody still uses it. you have to:
- get an orange/grapefruit/ball of similar size
- place orange on the floor
- place feet either side of ornage just slightly more than should width apart so you are standing just behind the orange
- arms behind your back, elbows bent so you can hold on to each arm with the oppoaite hand - this means you r back is straight and you shoulders are back as they should be when you are riding
- bend at the knees keeping your back straight and shoulders back
- pick up the orange between your knees
- stand up as far as you can - you wont be able to stand up completely straight becuase of the orange.
- repeat by putting the orange back on the floor, then start again
LOL i used to do this all the time, its really hard but lots of fun . other than that, you need a strong core and strong legs , upper body not so important