It might be about 15 years ago when a friend of us, who is a building contractor suggested that I would dig some eight holes for the foundation of our summerhouse just by hand with a shovel.
I thought then he was mad. That would be a back-breaking impossible mission. Now, all those years later I have dug much more than just those holes and... I find it fun and my back is just fine.
The most important term is time.
You cannot expect this to happen a quickly as with a JCB. So pace yourself.
The second important one is amount. Don't overfill your shovel or wheelbarrow. Take less at a time and you get less exhausted.
In addition I changed frequently my working position and sometimes I filled a bucket in the trench and moved earth this way. Around piping I used a small masonry trowel, which made things very easy.
The bonus of my digging is that I found an ancient wall, obviously a foundation of an earlier house. I didn't move it around as that would be against the law, so I took pictures and then I will fill the trench with gravel to drain any water away from the foundation.
Great fun in great summer weather.