In studies of human motor control, motor synergy hypothesis has been proposed as a solution of the well-known degree-of-freedom problem. On the other hand, controlling complex robots using optimal control also has the increased difficulty of facing the well-known problem of dimensionality. In this paper, performance of motor synergies in application of generating goal-directed movements using optimal control is examined. Results show that computational expense could be reduced while success rate is maintained, when motor synergies with properties of achieving goal optimally are utilized. The performance of utilizing motor synergies with different properties is also investigated. It is found that the same goals can still be achieved utilizing motor synergies which possess energy efficiency properties, with satisfactory success rate and computation expense.