We have a Zebris FDM-T treadmill running Noraxon MR 3.10 software, and we have developed an app in Excel to calculate Center of Pressure variability at 10% intervals. We downloaded .csv files from the software, which calculates x and y coordinates from the edges of the force sensor array, and our participants typically have about 70 sequential points for each of 250-260 steps (about 5 minutes each trial.)

Our app works well. But, because it uses the calculated CoP at initial contact as the reference point for all subsequent points (x is P-A progression, y is M-L) the CoP variability it calculates is affected by step-to-step variations in foot rotation position (but it is not affected by variations in medial-lateral or posterior-anterior foot placement.) Therefore, this CoP calculation are not comparable to those that are calculated from the edge of the foot (e.g., Becker, G & P, 2014; Koldenhoven, 2018, Electromyography & Kinesiology.) But the inclusion of the effect of foot rotation doesn’t seem like a bad thing to us – we are clinicians, not engineers, and this combo CoP measure intuitively seems clinically meaningful. Does anyone else have a more informed opinion? Thank you.

Brent S. Russell, MS, DC
Professor, Life University, College of Chiropractic
Dr. Sid E. Williams Center for Chiropractic Research
office (770) 426-2641