  We study the dynamics of a `composite' or `dressed' quark in strongly-coupled
large-N_c N=4 super-Yang-Mills, making use of the AdS/CFT correspondence. We
show that the standard string dynamics nicely captures the physics of the quark
and its surrounding non-Abelian field configuration, making it possible to
derive a relativistic equation of motion that incorporates the effects of
radiation damping. From this equation one can deduce a non-standard dispersion
relation for the composite quark, as well as a Lorentz covariant formula for
its rate of radiation. We explore the consequences of the equation in a few
simple examples.
