Digging is the garden task that injures most backs, because it is heavy, bent and usually done in a single annual burst. The way through is to count the work before starting and spread it, rather than discovering the total halfway through.

How much digging does a small allotment really involve?
More than it looks. A west London notebook that keeps figures for a small urban plot puts a ten-rod allotment at about 253 square metres of ground to manage. Turned by spade at a steady pace, that is several full days of bent work, not one Saturday.
The number is the point: once the plot is a workload on paper, spreading it stops feeling like cheating.
How can heavy garden work be spread to spare the back?
Break the plot into strips and do one strip a day. Alternate twenty minutes of digging with a lighter job: hoeing, compost-turning, watering. And take seriously the option of not digging at all: mulched beds and a hoe do most of what the spade does on ground that is already in cultivation.
Our page on why your back hurts the day after gardening covers the pacing habit in more detail.
Which habits change the load on the spine?
Three: a spade that is the right length for your height, lifting the fork or spade load at thigh height rather than throwing from the ankles, and a hard stop before tiredness turns technique sloppy. Most digging injuries happen in the last third of a session.
When is garden soreness just soreness?
Ordinary digging stiffness settles over a day or two. Pain that is sharp on movement, goes down a leg, or is still strong after a week is a different matter and deserves a GP's opinion rather than another dose of the same work.
The National Allotment Society publishes practical guidance on running a plot, from soil care to tenancy, at nsalg.org.uk.
The indoor cousin of the same problem, lifting heavy kit at home, is in the hobby that weighs twenty kilos.