Humans have been splitting wood since they mastered the concept of fire.
It doesn't mean, however, that you should continue chopping wood with chiseled stones.
You can continue splitting firewood like a caveman. Or, you save your back by using your brain.
The simplest solution is a manual log splitter.
They are very similar to the tire jack in your trunk. You create pressure by manually cranking two poles like a cross country skier.
Frankly, we're not the biggest fans of manual log splitters. We recommend getting an small electric log splitters
Basically, a simple electric motor replaces your muscle power, so you can save your stamina for more important things.