In August 218 researchers from the USA published the results of their study to assess the effect of different treadmill running speeds on the coordination and variability of coordination in healthy runners. Fourteen healthy runners ran on a split-belt force instrumented treadmill at five different speeds. Continuous relative phase was used to quantify coordination and variability during the three phases of stance (loading, mid stance, and propulsion). Results showed that the thigh internal/external rotation (shank abduction/adduction) was different during the propulsive phase and that thigh flexion/extension showed the greatest differences in coordination and variability during the five different speed levels of the treadmill. In addition, significant differences were seen in thigh flexion/extension (toe-off) and thigh flexion/extension (foot inversion/eversion). It was also noted that the decreases in coordination and variability were accompanied by changes in the centre of mass vertical motion during stance, but not knee flexion angles. The researchers therefore concluded that increases in running speed led to a more constrained running pattern through a reduction in the degrees of freedom in movement.
Bailey JP et l. Effects of treadmill running velocity on lower extremity coordination variability in healthy runners. Hum Mov Sci. 2018 Aug 6;61:144-150.