We present competition protocols to speed up the execution of sequential programs on a network of shared workstations in the background by exploiting their wasted computing capacity, without interfering with processes of workstation owners. In order to argue that competition protocols are preferable to migration protocols in this situation, we derive the closed form solutions for the speedup of competition protocols and migration protocols, and simulate both of protocols under comparable overhead assumptions. Based on our analytic results and simulation results, we show that competitive execution is superior to process migration, and that competitive execution can finish sequential programs significantly faster than noncompetitive execution, especially when the foreground load is sufficiently high.