Earlier this year, the Government announced that it wanted big reductions in the nine-subject compulsory primary curriculum so that schools could concentrate on literacy and numeracy.
But Peter Hain, the education minister for Wales, said yesterday that schools must carry on with running, throwing and jumping even when the slimmed-down curriculum is introduced in September.
Advice on how English schools should teach these other subjects is expected to be published by Government curriculum advisers later this summer.
Mr Hain said: "Many young children take very little exercise. Habits formed by children at primary-school age persist into later life. I am determined that our youngstersshould not become the next generation of couch potatoes. I want Wales to produce a nation of fit children who will go on to become top sportsmen and women to represent Wales."
He said the changes would still leave plenty of time for reading, writing and arithmetic.
His announcement came as a report by the Chief Inspector of Schools in Wales said general fitness was unsatisfactory or poor among primary children.