Figure 1

Experimental setup and major locomotion parameters. (A) Rat walking on split-belt treadmill by the hindlimbs. The rats rested their forepaws on the bar in front of them and wore a harness connected with a flexible beam fixed on the treadmill. (B) Marker positions and definitions of angles. (C) Experimental procedure of one session (2.0x condition), where the two belts moved at 10 m/min in the ST and at 20 m/min in the FT, and one belt moved 2.0 times faster than the other belt moving at 10 m/min during the SB. ST: slow-tied configuration, FT: fast-tied configuration, SB: split-belt configuration. (D) Temporal parameters. \({t}_{i}^{{\rm{TD}}}\), \({t}_{i}^{{\rm{LO}}}\), and \({t}_{i}^{{\rm{MST}}}\) (i = fast, slow) are the time at touchdown, liftoff, and middle of stance phase, respectively. t^GCD is the gait cycle duration. Relative phase between the two legs is calculated by \(2{\rm{\pi }}({t}_{{\rm{fast}}}^{{\rm{MST}}}-{t}_{{\rm{slow}}}^{{\rm{MST}}})/{t}^{{\rm{GCD}}}\). Duty factor is calculated by the ratio of the stance phase relative to the gait cycle duration. Liftoff timing of the fast leg and touchdown timing of the slow leg relative to touchdown timing of the fast leg is calculated by \(2{\rm{\pi }}({t}_{{\rm{fast}}}^{{\rm{LO}}}-{t}_{{\rm{fast}}}^{{\rm{TD}}})/{t}^{{\rm{GCD}}}\) and \(2{\rm{\pi }}({t}_{{\rm{slow}}}^{{\rm{TD}}}-{t}_{{\rm{fast}}}^{{\rm{TD}}})/{t}^{{\rm{GCD}}}\), respectively. (E) Spatial parameters (stride length and step length). Stride length is defined by the distance from the touchdown position to the liftoff position of the foot for each leg. Step length is defined by the distance between the foot positions of the two legs at the touchdown of one leg along the direction of belt movement (fast/slow step length means the step length at the touchdown of the fast/slow leg). White arrows show the moving direction of the belts.