COM (center of mass) between the feet (inside step width?)
/Center of Mass between the feet . . .
The coordinated movement of the spine and pelvis during running. Preece SJ1, Mason D2, Bramah C3.
Hum Mov Sci. 2016 Feb;45:110-8. doi: 10.1016/j.humov.2015.11.014. Epub 2015 Nov 24.
"There appeared to be an anti-phase relationship in the frontal plane between thorax and pelvic motion (Fig. 1b and h)
during stance. Specifically the thorax was laterally flexed towards the stance limb during early stance AND THEN MOVED
TOWARDS A NEUTRAL position during the latter half of stance, as the pelvis became elevated on the contralateral side. The coordination analysis classified the frontal plane pelvis–thorax motion as either anti-phase or pelvis-only during stance (Fig. 4b). This latter classification resulted from the increased motion of the pelvis compared to the thorax which resulted in a more
vertically aligned coupling vector (Seay et al., 2011b) and therefore a coupling angle which was classified as pelvis-only
motion."
This study supports our well founded beliefs that the COM moves within the confines of the step width, it moves TOWARDS, but not over the foot in the early stance phase, and then moves back towards a neutral position during the latter half of stance. One must fully understand the implications of the antiphasic nature in the planes of motion of the body during running (and walking) to understand what the COM is truly doing, what it is not doing, and what it should not be doing.
This study concluded,
"This is the first study to provide an underlying biomechanical rationale for the coordination pattern between the pelvis
and thorax during running in all three body planes. The data showed an anti-phase relationship between these two segments in the sagittal and frontal planes and we suggest that this in a consequence of the requirement to minimise accelerations of the CoM in the AP and ML directions."
The coordinated movement of the spine and pelvis during running. Preece SJ1, Mason D2, Bramah C3.
Hum Mov Sci. 2016 Feb;45:110-8. doi: 10.1016/j.humov.2015.11.014. Epub 2015 Nov 24.
