Comparison of forelimb and hindlimb movements during treadmill and overground locomotion at different speeds in intact adult cats

To evaluate locomotion, motorized treadmills have been widely used in research due to several advantages over conventional overground locomotion. Although comparisons have been made, whether locomotion is equivalent on the treadmill and overground at different speeds remains poorly understood. In the present study, we collected kinematic and electromyography (EMG) data in 10 intact adult cats at four matched speeds ranging from 0.5 m/s to 0.8 m/s during motorized treadmill and overground locomotion. During treadmill locomotion, fore- and hindlimb cycle and stance durations were longer, whereas swing duration was reduced at matched speeds. Cats preferred more stable support periods (i.e., with more limbs on the ground), such as triple and quadrupedal support during treadmill locomotion, whereas they favored diagonal support during overground locomotion, which is known to contribute to forward propulsion and locomotor efficiency. The type of gait and footfall pattern was conserved between locomotor tasks. The fore- and hindlimbs took longer steps and strides during overground locomotion, but paw placement at contact was more rostral during treadmill locomotion. Fore- and hindlimb extensor muscle burst durations likely reflect the proportionally longer stance phase observed during treadmill locomotion. EMG burst amplitude was greater in fore- and hindlimb extensor muscles during overground locomotion, whereas EMG burst amplitude of flexor muscles was greater during treadmill locomotion. Overall, our findings demonstrate distinct neuromechanical strategies between treadmill and overground locomotion, reflecting differences in stability requirements, propulsion, braking, and fore- and hindlimb positioning in quadrupedal mammals.