Traction force dynamics in wild-type cells migrating on adhesive substrates. (A) Kymograph of the instantaneous magnitude of the traction stresses and axial tension for a wild-type cell chemotaxing on a highly adhesive substrate, showing that the cell alternates between the NS and SK modes. The inclined red and black lines indicate the instantaneous position of the front and back cell edges. (B) Left, middle, and right columns show the mean magnitude of the total, axial, and lateral stresses, respectively, in cell-based coordinates for the cell depicted in A during the NS (top) and SK (bottom) modes. (C) Box plots of the time duration of the NS (blue) and SK (red) modes (n = 9 cells). (D–I) Box plots of motility parameters corresponding to the NS and SK modes (n = 9 cells). Each parameter is normalized with its mean value for each cell. (D) Migration speed, V/V〉. (E) Aspect ratio, AR/AR〉. (F) Strain energy, U_s/U_s〉. (G) Axial force, F_x/F_x〉. (H) Lateral force, F_y/F_y〉. (I) Ratio of axial to lateral force, (F_x/F_y)/F_x/F_y〉. One or two asterisks denote statistically significant differences between medians (<0.05 or <0.01, respectively). (J) Table showing mean migration speed (V), aspect ratio (AR), cell area (A), strain energy (U_s), axial and lateral force (F_x and F_y) for n = 11 cells on poly-L-Lys–coated substrate versus control (collagen only, n = 12).