Fig. 7. Limping behavior, observed extremely rarely, under saturating ATP. Every second step occurs at 12 s^-1, intervening steps require much longer periods. The existence of such data suggests that every second step occurs from a similar biochemical state, which is consistent with models predicting that the two heads alternate roles with each unitary advance. The step distance in this data, taken with the dual-bead trapping geometry, is probably compromised by elastic linkages in the system.