You're doing it wrong.
my back and arse hurts from playing chess what should i do?
Sort:
Patient: Hey Doc, my head is really hurting from banging it against the wall.
Doctor: So stop banging it against the wall.
quit playing chess
Take a walk after each move
Find somewhere else to put the captured pieces.
Inject copious amounts of morphine before playing.
Nigel?
You need to work on your positioning. In what state are your legs? If one of them is being constricted too much that's your "bad leg". If it's bad enough, perhaps gangrene setting in, it may be worth trying to exchange it off. Undoubtedly the leg pair offer some advantage, but it's quite possible to obtain an excellent position without it.
Some examples may prove instructive. First a timeless classic:
Note the excellent position of Zukertort (left), in contrast to his opponent who is somewhat awkwardly, whose chin is being supported by his right hand.
And here's our friend Karpov, in his famous match with Fischer. See his positioning: very tense and both players aren't giving anything away as yet, but make the slightest mistake and he'll destroy his opponent.
Squats and dead lifts.
Eating tacos usually helps
Sounds painful
Now, eating tacos. Doesn't hurt!
lie on your stomach while you play until your back and arse are all better
try placing the pole between your boobs instead of bustin your butt. it should hurt a lot less.
get a more comfortable chair for heaven sakes
An injection in the bum to make it numb is also worth trying.
Roger Waters would've called it comfortably numb.
im confused