One of the themes of The Loneliness of the Long-Distance Runner is the struggle of the individual against the system. As a young working-class lad, Smith feels kept down in this class-conscious society. Though he lives at a time of full employment, with jobs in plentiful supply, he's still alienated from an economic and political system which he doesn't believe serves the interests of his social class. Smith has a very simplistic view of society, in which the upper and middle-classes lord it over working-class folk such as himself. His is very much a "them and us" attitude: an attitude of antagonism towards those above him in the social hierarchy.
In such a society, Smith feels he has no alternative but to assert his individuality and his working-class identity through committing crime. It's notable that Smith's a burglar, which shows his contempt for other people's property and the social system on which it is founded. Burglary, like the long-distance running in which Smith participates, is also a solitary activity, where Smith can briefly feel free from the stifling social norms that restrict the expression of his true identity. Whether it's as a burglar or as a long-distance runner, Smith shows that, although he can never break the system, he will never be broken by it.