The three classes of dynamic cellular response could be captured by the model for all cell shapes considered, including circular (top row) and spindle-shaped (bottom row) cells.

<p>Populations of stress fibers were studied with the same mean pre-stretch, but with three different standard deviations. Monotonic reinforcement (first column), reinforcement followed by retraction (second column), and monotonic retraction (third column) were all predicted, depending upon the variation in pre-stretch within the fibers. Cells in which many stress fibers ruptured in tension underwent monotonic retraction. Cells in which no stress fibers ruptured in tension underwent monotonic reinforcement. All other cellular responses lay between these two extremes, and involved reinforcement following retraction.</p>