  Mechanical unfolding of polyproteins by force spectroscopy provides valuable
insight into their free energy landscapes. Most phenomenological models of the
unfolding process are two-state and/or one dimensional, with the details of the
protein and its dynamics often subsumed into a zero-force unfolding rate and a
single distance $x_u^{1\textrm{D}}$ to the transition state. We consider the
entire phase space of a model protein under a constant force, and show that the
distance $x_u^{1\textrm{D}}$ contains a sizeable contribution from exploring
the full multidimensional energy landscape. Proteins with more degrees of
freedom are expected to have larger values for $x_u^{1\textrm{D}}$. We show
that externally attached flexible linkers also contribute to the measured
unfolding characteristics.
