  Molecular motors transduce chemical energy obtained from hydrolizing ATP into
mechanical work exerted against an external force. We calculate their
efficiency at maximum power output for two simple generic models and show that
the qualitative behaviour depends crucially on the position of the transition
state. Specifically, we find a transition state near the initial state
(sometimes characterized as a "power stroke") to be most favorable with respect
to both high power output and high efficiency at maximum power. In this regime,
driving the motor further out of equilibrium by applying higher chemical
potential differences can even, counter-intuitively, increase the efficiency.
