Methods for collecting footfall data have come a long way since the days of using ink or carbon paper to make footprints on paper which were then measured with wooden rulers. Today, the gold standard for collecting accurate Spatio Temporal Gait (STP) is an electronic, pressure-sensing walkway, such as the ProtoKinetics Zeno Walkway System. The Zeno Walkway System provides a direct measure as to where and when the foot is making contact with the ground. This allows STPs to be calculated directly without using algorithms or manual methods to determine important gait events, such as foot-strike and foot-off.
Measuring Footfalls Temporally and Spatially
As a subject walks across the pressure mat, the foot-ground contact activates individual pressure sensors. ProtoKinetics Movement Analysis Software (PKMAS) is able to store that array of activated sensors from the walking trail, knowing the time each sensor was activated, the level of pressure on it, and the sensor’s location within the walkway. The software groups the activated sensors together and labels the grouped sensors as right or left footfalls. The first sensor within a footfall group denotes a foot-strike. The last sensor of the footfall deactivating denotes a foot-off. Combining the foot-strike and foot-off information from all of the right and left footfalls allows for the calculation of the temporal and stance phase variables described in our earlier post, Measuring Spatiotemporal Parameters: Time & Stance Phase.
Groups of sensors can also be viewed spatially. When looking at the sensor array in this way, the PKMAS software is able to locate heel, toe, foot mid-line, and center locations. The spatial analysis of the sensors is like that of the old technique of stepping in ink before walking across a paper floor. After the software identifies key locations on each of the footfalls, distances between those locations can be used to calculate the spatial parameters as described in our previous post, Measuring Spatiotemporal Parameters: Spatial Parameters, Speed and Walk Ratio. The advantage PKMAS provides is to separate footfalls both temporally and spatially. For instance, if a subject has a stride length that is shorter than their foot length, it results in footprints overlapping. By separating footfalls temporally and spatially, PKMAS is able to separate overlapping footfalls and provide STPs for walking patterns that would have previously been very difficult or impossible to measure accurately.
Measuring Center of Pressure
In addition to STPs, the Zeno Walkway System offers measures using specific pressure data. Because each sensor is able to differentiate between levels of pressure, a center of pressure (COP) can be calculated at any given time using all of the activated sensors (on the walkway mat or within a specific region, like a single footfall), and the level at which they are activated. The COP trajectory can be tracked over time and can be viewed within specific periods of the gait cycle using the temporally defined time points. This allows the PKMAS system to describe how the foot is interacting with the ground, in addition to when and where the interaction is taking place.
Directly measuring where and when the foot interacts with the ground is the most accurate way to calculate temporal and spatial values. The Zeno Walkway System simplifies the process of collecting and reporting these important variables.