Ergonomics is not limited to our musculoskeletal systems. Anatomically, humans are designed to squat when pooping. There are people in many cultures who still squat to void or eliminate. It is interesting to note that many of these third world cultures don't suffer from hemorrhoids, constipation, colitis, appendicitis, colon cancer, fistula, diverticulitis or other ailments we civilized Western Culture people do.
It is a popular misconception that a plumber named Thomas Crapper invented the toilet but it is not true. Crapper did not invent the flush toilet. He did, however do much to increase the popularity of the toilet. The toilet was invented by Sir John Harington. Look it up on the URBANLEGENDS website.
The modern toilet is great for people with bad knees and hips but it does nothing to promote good colon health and does everything to hamper it. Consider the garden hose. If you step on it or kink it, the flow of water will diminish considerably. If you look at a picture of your colon, you'll notice a series of kinks. The very last kink before the anus has the puborectalis muscle wrapped around it. This muscle aids in the effort to maintain continence. While you stand or sit, this muscle is engaged and helps to hold everything in.
When you sit on a toilet, you are sitting at a 90 degree angle and the puborectalis muscle is only partially relaxed and still attempting to hold everything in so you have to push to get stuff out. But when you sit at a 30 degree angle, the muscle is fully relaxed and the final bend in the colon is now straight so whatever is in there can now effortlessly fall out.
If you've ever been on the toilet with cramps, you instinctively know that it is more comfortable to curl down so that your chest is touching your knees. That is your body trying to do what it knows is the right thing but the torture device you are sitting on is preventing that for even in this almost proper position the kink in the colon is maintained.
If your home is equipped with a western civilization toilet and not one like you may find in India, for instance, experiment with putting your feet up on a step-stool, stepladder, box or trash can. You should try to sit upright with your knees at a 30 degree angle.
So the next time you feel like the crap was beaten out of you, try this posture and maybe you won't feel so pooped (sorry, I had to do that).