Werm has it right. Why lift all those logs when it is not necessary?
Jake has it right even though he does part of his splitting the wrong way.
Eric is right too! My back is already bent. I have a terrible back and sometimes have to go days or even weeks doing practically nothing due to back pain (part from polio, part from an injury).
I do place the splitter so the wheel is right tight against the pile of logs. The newer splitters are not as wide as my older one so you could get those even closer. This picture may not the best to show but if you look closely you can see how I do it. Notice there are 4 rows of logs. I split 2 rows at a time, moving the splitter as I go. At present I am working on the second set of 2 rows so when I get these 2 rows done there is only a part of one row left to split. Then I'll start the stacking chore.
The splitter is tight to the stack. The first row I just reach out and grab a log. The second row is a bit of a reach. Not long ago people were posting about a hook for grabbing. When I split the axe is usually right by me and if I can't get a log from the second pile, rather than getting up, I can just reach with the axe and pull it to me far enough so I can then get a hand on the log.
When I get a log off the stack, I simply let it fall to the ground and then most of the time using only my left hand will roll it onto the splitting block.
I do not constantly get up and down although from time to time I will get up; usually for a drink of water. Also I have to get up every so often to move the splitter ahead when I run out of wood which is what has to be done no matter the method used.
I do not get a sore back from bending. I pretty much sit the same as if I were in a chair. How is that bending bad? I do not understand when this is claimed.
I have a time or two split some big logs right where I cut them. For this I usually just get down on my knees to do just a couple of logs.