A brief explanation of the different Sparta Scan metrics that display in the Movement Health Platform.
Introduction
Force Plates
A Force Plate or platform is a device used to measure the forces exerted on the ground by a human body. Force plates can be thought of as high-powered bathroom scales because the devices themselves are relatively simple. The force plate device is instrumented with load cells that convert a force, such as pressure, into an electrical signal that can be measured and standardized. As the force applied to the load cell increases, the electrical signal changes proportionally.
Read More: Force Plate Technology
Data Types
Our data model describes the different levels of data that can be calculated utilizing the force plate, but at the simplest level, a force plate is designed to measure forces over a period of time. These two variables, force and time, are measured directly, and can then be utilized to calculate a variety of different metrics or variables based on Newtonian physics. It is important to note that the definition and calculation of the different “raw metrics” that can be calculated from the underlying force-time data are not necessarily standardized or agreed upon globally. The following are the definitions for the metrics that are available when utilizing the Sparta Movement Health Platform.
Read More: What types of data does Sparta provide?
Helpful Visualizations:
Vertical Force (z) vs Time: The above visual shows a generic Jump Scan force-time curve illustration generated by plotting the time-series data. Specific phases and points of interest are labeled above to provide a visual to better understand how the raw data metrics are calculated and what they potentially represent.
Center of Pressure (x,y) over Time: The above visual shows a generic center-of-pressure illustration generated by plotting the center of pressure data collected over a time window visually onto the x and y axes to show the CoP or Sway path. An important note is that data is collected in all three planes (x, y, and z) for all of the different Sparta Scans. The black line shows the path of the center of pressure during the assessment, in this example a Balance Scan.
Movement Panel Metric (Raw Data) Descriptions
GENERAL
Body Weight: Body mass multiplied by g (g = gravitational constant). Measured in N.
Body Mass: Body weight divided by g (g = gravitational constant). Measured in kgs.
JUMP SCAN
Jump Height: Jump height calculated by the integration of acceleration to determine exit velocity. Measured in cm. Learn more here: How does Sparta measure jump height?
Load (Avg Braking RFD): The average rate of force change from braking point to zero velocity (concentric) point. Measured in N/s. Learn more here: Load, Explode, and Drive
Explode (Avg Relative Concentric Force): The average force for concentric phase divided by body mass. Measured in N/kg. Learn more here: Load, Explode, and Drive
Drive (Relative Concentric Impulse): The integral of force in the concentric phase divided by body mass. Measured in Ns/kg. Learn more here: Load, Explode, and Drive
Max Change in Acceleration: The maximum change in acceleration during the eccentric phase. Measured in m/s³.
Max Acceleration: The maximum acceleration achieved during the jump. Measured in m/s².
Eccentric Impulse: The integral of Force divided by body mass in the eccentric phase. Measured in Ns/kg.
Concentric Impulse: The integral of Force divided by body mass in the concentric phase. Measured in Ns/kg.
Max Velocity: The maximum velocity of center of mass during jump. Measured in m/s.
Max Power: The maximum product of Force and velocity divided by body mass achieved during jump. Measured in W/kg.
Unweighing Time: The duration of time from the start of unload to start of eccentric phase. Measured in s.
Eccentric Time: The duration of the eccentric phase of jump. Measured in s.
Concentric Time: The duration of the concentric phase of jump. Measured in s.
Time to Takeoff: The duration of time from start of unload to liftoff. Measured in s.
Time to Max Acceleration: The time from start of unload to max acceleration is reached. Measured in s.
Countermovement Depth: The distance the center of mass moves downward in the countermovement. Measured in m.
mRSI - Modified Reactive Strength Index: Jump Height divided by Time to Takeoff. Measured in m/s or arbitrary units.
Jump Height (Flight Time): Jump height calculated from the flight time. Measured in m.
COPx Shift Start: Lateral weight shift from the start of unload to the braking point. Measured in m.
COPy Shift Start: Forward weight shift from the start of unload to the braking point. Measured in m.
COPx Shift Acceleration: Lateral weight shift from the braking point to liftoff. Measured in m.
COPy Shift Acceleration: Forward weight shift from the braking point to liftoff. Measured in m.
COPx Sway Velocity: Leftward sway velocity from braking to concentric point.
COPy Sway Velocity: Forward sway velocity from braking to concentric point.
BALANCE SCAN
Sway Velocity Mean: The average sway velocity magnitude for 5 second period on one side. Measured m/s.
Multivariate Multiscale Entropy: A multivariate, multiscale sample entropy measurement for center of pressure (x-y axes) and vertical force over target window. Measured in arbitrary units.
Multiscale Vertical Entropy: A multiscale sample entropy measurement for vertical force signal over target window. Measured in arbitrary units.
Multivariate Multiscale Entropy in X-Y plane: A multivariate, multiscale sample entropy measurement for center of pressure (x-y axes) over target window. Measured in arbitrary units.
COPx shift: The shift in x-axis (ML) center of pressure (COP) when moving from two legs to one. Measured in m.
Right: Above metrics for Right side only during balance.
Left: Above metrics for Left side only during balance.
Symm: Above metrics comparing Right and Left side measure of relative similarity between values of the metric; where 1.0 represents maximum symmetry and 0 represents minimum symmetry.
Sway Velocity - 2 Leg: The average sway velocity magnitude while balancing on two legs during any weigh-in segment. Measured in m/s.
Multivariate Multiscale Entropy - 2 Leg: A multivariate, multiscale sample entropy measurement for center of pressure (x-y axes) and vertical force over target window on two legs during any weigh-in segment. Measured in arbitrary units.
PLANK SCAN
Mass Fraction: The average fraction of bodyweight on the plate during plank. Measured as a fraction of 1.0.
Sway Velocity Mean: The average sway velocity magnitude for 5 second period on one side. Measured m/s.
Mass Fraction Divided by Sway: The Mass Fraction divided by the Sway Velocity Mean. Measured in s/m or arbitrary units.
Negative Log Sway Mass Fraction: The Mass Fraction multiplied by the negative log of average sway velocity.
Multiscale Vertical Entropy: A multiscale sample entropy measurement for vertical force signal over target window. Measured in arbitrary units.
Multivariate Multiscale Entropy: A multivariate, multiscale sample entropy measurement for center of pressure (x-y axes) and vertical force over target window. Measured in arbitrary units.
Multivariate Multiscale Entropy in X-Y Plane: A multivariate, multiscale sample entropy measurement for center of pressure (x-y axes) over target window. Measured in arbitrary units.
COPx Shift: The shift in x-axis (ML) center of pressure (COP) when moving from two legs to one. Measured in m.
Right: Above metrics for Right side only during plank.
Left: Above metrics for Left side only during plank.
Symm: Above metrics comparing Right and Left side measure of relative similarity between values of the metric; where 1.0 represents maximum symmetry and 0 represents minimum symmetry.