Virtual digging
Usually done at night to maximise the 'what the hell are they doing' factor on neighbours.
You will need:
Ideally a patch of rough ground
A hose with a sprinkler attached
A large heavy thing, ideally not water soluble
A pile of assorted sized rocks
Copious quantity of orange poster paint
Shovels and rakes and implements of destruction
A lump hammer
Optional, if available, an accomplice
Procedure
Start sprinkler as soon as possible to ensure ground is saturated. If sprinkler isn't available construct something from a washing up liquid bottle and some sticky-backed plastic.
Move large heavy thing and rocks to a position uncomfortable in the spray line
Daub yourself liberally with the poster paint, this should be repeated regularly throughout the session.
Using the shovels, rakes and other implements of destruction, move the rocks from one place to another place.
Move the large heavy thing to where the rocks were.
Move the rocks to the place vacated by the large heavy thing.
Repeat until you are knackered
Repeat for another hour.
Periodically hit yourself with the lump hammer to simulate walking into things.
If an accomplice is available, they can simulate rock falls by throwing rocks at you and clocking you on the bonce with the lump hammer. Simulation of fellow diggers can be achieved by hurling abuse and smaller rocks.
When you are only just able to walk, stop and attempt to wash the paint off.
Finally, sit down with a beer, you've earned it.
Once you have mastered this level, you can move on to more challenging levels, by repeating the above while remaining on your knees for the duration and then by lying down.
Further enhancements can be added to reflect the an actual dig site, such as the Frongoch - a 200m flat out crawl.
Don't look so embarrassed, it's a family trait...