Lots of people put a lot more effort into using their spades than is necessary so i'm going to give you a few tips on efficient, safe digging for the average home user.
Digging is hard work and also a good workout but you will need some forms of protection before you can go for a while. First of all you will need gardening gloves to keep your hands from getting massively blistered. It would also help to have Sturdy footwear if you have any.
To effectively use a spade you need to keep it verticle when digging into the ground. This works best if you hold the handle with both hands then push the blade down with your foot. After this your going to want to use the lever system here. Hold the spade at the handle and leverage the soil up so it requires as little effort as possible.To lift the soil simply bend your knees and slide one hand down the blade. Remove the soil by walking a few paces. If you repeatedly twist your torso to drop it next to you it wont take long before you start to feel muscle strains. If you follow this simple guide then digging shouldn't be too hard on you although it is not the easiest of gardening tasks.