So we have 100 milliseconds, 200 milliseconds, 300 milliseconds, and so forth. So the blue graph is the action potential as it is generated on the membrane of that skeletal muscle cell. And the red graph, e, is the graph that describes our muscle contraction. And notice what we see from this diagram. We see that the muscle contraction takes place after the action potential actually occurred. So basically, we have the cell membrane of that skeletal muscle.